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1. ee ae A a i r r f SEAL fry EEFT i NAGY AKAN j T f fi f f li l T ri iff i jj i k A A LV MOE i ik j AY AAA AA AA Wh AWN hh h TA R iNi Hij Iil HJ l TA Ij ETT HTT w WANA ih TT dT ENIN NANN iil HALL J HIT MTT f HT I jii H TTT I iii Ii HII i LITT missy I II T il Ii fi li j iti Hi i HIT ELH Hi HI I l HH li TEL Getting Started with C Audio Programming for Game Development A hands on guide to audio programming in game development with the FMOD audio library and toolkit Getting Started with C Audio Programming for Game Development A hands on guide to audio programming in game development with the FMOD audio library and toolkit PACKT PUBLISHING BIRMINGHAM MUMBAI www allitebooks com Getting Started with C Audio Programming for Game Development Copyright 2013 Packt Publishing All rights reserved No part of this book may be reproduced stored in a retrieval system or transmitted in any form or by any means without the prior written permission of the publisher except in the case of brief quotations embedded in critical articles or reviews Every effort has been made in the preparation of this book to ensure the accuracy of the information presented However the information contained in this book is sold without warranty either express or implied Neither the author nor Packt Publishing and its deale
2. It is in the Update method where all of the fading takes place The process follows these rules e Ifasong is playing and we are fading in increase the volume of the current song a bit Once the volume reaches one stop fading e Ifasong is playing and we are fading out decrease the volume of the current song a bit Once the volume reaches zero stop the song and stop fading 37 Audio Control e If no song is playing and there is a song set up to play next start playing it void AudioManager Update float elapsed const float fadeTime 1 0 in seconds if currentSong 0 amp amp fade FADE IN float volume currentSong gt getVolume amp volume float nextVolume volume elapsed fadeTime if nextVolume gt 1 0f currentSong gt setVolume 1 0f fade FADE NONE else currentSong gt setVolume nextVolume else if currentSong 0 amp amp fade FADE OUT float volume currentSong gt getVolume amp volume float nextVolume volume elapsed fadeTime if nmextVolume lt 0 0f currentSong gt stop Current Ssong 0 currentSongPath clear fade FADE NONE else currentSong gt setVolume nextVolume else if currentSong 0 amp amp nextSongPath empty PlaySong nextSongPath nextSongPath clear system gt update Controlling the master volume of each category Controlling the master volume of each
3. Chapter 6 Let us start by creating a variable and some methods to control the volume The volume will be stored as a floating point number between 0 silence and 1 full volume The Set Volume method makes sure that the value is always inside this range We should also reset the volume to 1 whenever a sound begins playing public float GetVolume const return volume void SetVolume float value if value lt 0 0 volume 0 Of else if value gt 1 0f volume 1 0f else volume value private float volume In order to play the sound at this volume all we have to do is multiply each of the original values in the audio data by the value of the volume variable before we write them to the output Because the volume variable is a floating point number we need to cast the result back to PCM16 after the multiplication void MyChannel WriteSoundData PCM16 data int count if sound paused return for Unt i s 04 i s eount gt i te 2 4 if position gt sound gt count TE LOop 4 position 0 else Stop J3 return PCM16 value PCM16 sound gt data position volume data i value data i 1 value position 85 Low level Audio Changing pitch Changing the pitch of a sound is slightly more complicated than changing its volume The most basic way to modify the pitch of a sound although the speed of the sound is also affected is to control how fast we adva
4. Installing FMOD Ex Programmer s API Installing a C library can be a bit daunting at first The good side is that once you have done it for the first time the process is usually the same for every other library Here are the steps that you should follow if you are using Microsoft Visual Studio 1 Download the FMOD Ex Programmer s API from http www fmod org and install it to a folder that you can remember such as C FMOD 2 Create anew empty project and add at least one cpp file to it Then right click on the project node on the Solution Explorer and select Properties from the list For all the steps that follow make sure that the Configuration option is set to All Configurations 14 Chapter 2 3 Navigate to C C General and add Cc FMOD api inc to the list of Additional Include Directories entries are separated by semicolons 4 Navigate to Linker General and add c FMOD api 1ib to the list of Additional Library Directories 5 Navigate to Linker Input and add fmodex_vc 1ib to the list of Additional Dependencies 6 Navigate to Build Events Post Build Event and add xcopy y C FMOD api fmodex dll OutDir to the Command Line list 7 Include the lt fmod hpp gt header file from your code Creating and managing the audio system Everything that happens inside FMOD is managed by a class named FMOD System which we must start by instantiating with the FMOD System_Create function
5. volume min distance By changing the minimum distance we can control the overall size of the sound for example we could set a value of 0 1 for the sound of a fly or a value of 500 for the sound of an explosion When using this model the maximum distance should have a large value in order to give the sound enough distance to attenuate to silence We can make the sound attenuate slower or faster by changing the rolloffscale parameter in the System set3DSettings method The logarithmic model is realistic but has the disadvantage of making it harder to calculate the full range of the sound that is the distance to silence For this reason there are other models available that are easier to use such as the linear rolloff model which maps the minimum distance to full volume the maximum distance to silence and interpolates linearly in between We can select the linear rolloff model when creating the sound by adding the FMOD_3D_LINEARROLLOFF flag In this model the system rolloff scale does nothing if distance lt min volume 1 0 else if distance gt max volume 0 0 else volume distance min max min Setting the audio listener s properties Finally we must set the position velocity and orientation of the audio listener using the set3DListenerAttributes method of the system object FMOD VECTOR pos 3 0 470f 220E FMOD VECTOR vel 1 0f 0 0f 0 0 FMOD VECTOR forward 1
6. Then inside the WriteSoundData method we can apply these gains to the data before writing it to the output just as we did for the volume before Naturally we should only apply the values of leftGain and rightGain to their respective channels In addition because we need to cast to PCM16 after applying the gains there is no need to keep the cast from earlier void MyChannel WriteSoundData PCM16 data int count if sound 0 paused return for int i 0 L lt count i 9 d if position gt sound gt count 87 Low level Audio if lo p position 0 else Stop return float value sound sdata int position volume data i PCM16 value leftGain data i 1 PCM16 value rightGain position pitch With these out of the way we now need to create a floating point variable called pan and some methods to modify it The pan variable should take values between 1 full left and 1 full right Whenever the value of pan changes we call the private UpdatePan method to calculate new values for leftGain and rightGain public float GetPan const return pan void SetPan float value if value lt 1 0f pan 1 0f else if value gt 1 0 pan 1 0f else pan value UpdatePan private void UpdatePan float pan All that is left is to write the UpdatePan method There are a few different formulas to calculate the gain values for stereo p
7. int time 44100 buffer new PCM16 size memset buffer 0 size 2 The destructor deletes all the data allocated in the constructor MyDelay MyDelay delete buffer Finally the WwriteSoundData method does all of the work It begins by taking each sample in the output and mixing it with a portion of the sample stored in the buffer at the current position Next we take this new value and write it back to the output as well as to the buffer Finally we increment the position variable to the next sample wrapping around the end of the buffer void MyDelay WriteSoundData PCM16 data int count for int i 0 i lt count i Mix sample with the one stored in the buffer at position data i PCM16 data i buffer position decay Record this new value in the buffer at position buffer position datali Increment buffer position wrapping around position if position gt size position 0 91 Low level Audio To test this effect out simply create an instance of it in the main application and call the WriteSoundData method at the end of the audio callback When the application starts MyDelay delay new MyDelay 1 0f 0 50f Inside the audio callback for int i 0 i lt channels size i channels i WriteSoundData pcmData pcmDataCount delay gt WriteSoundData pcmData pcmDataCount Synthesizing a sound Before we end this chapte
8. A addGroup method 30 advantages FMOD cross platform 14 features 14 license 14 popularity 14 programming languages 14 supported formats 14 AIFF 11 ambient track of singing birds creating 61 analog audio signal 9 analog signal 9 APE 12 audio concepts analog signal 9 audio file formats 11 digital signal 9 multi channel audio 11 sound waves 7 audio data playing 75 76 representing 73 74 audio file errors checking for 18 audio file formats about 11 lossless compression 12 Index lossy compression 12 sequenced music 12 uncompressed audio files 11 audio files loading 16 streaming 16 17 versus sound events 54 55 audio listener 42 audio listener properties setting 45 audio manager building 19 improving 32 audio manager improvement project about 32 class definition 32 33 destruction implementing 33 initialization implementing 33 master volume controlling of category 38 songs loading 34 songs playing 36 37 songs stopping 36 37 sound effects loading 34 sound effects playing 35 sound effects stopping 35 audio manager project class definition examining 19 20 code samples 23 destruction implementing 21 initialization implementing 21 sounds loading 22 sounds playing 22 23 sounds streaming 22 audio mixing 89 audio source direction setting 44 audio source position setting 43 44 audio source range setting 44 audio sources about 42 creating 43 audio source velocity setting 43 44
9. FMOD LOOP NORMAL Seed random number generator for SFXs srand time 0 In the destructor we do the same thing as we did in the simple audio manager but this time there are multiple sound maps to clear AudioManager AudioManager Release sounds in each category SoundMap iterator iter for int i 0 i lt CATEGORY COUNT i for iter sounds i begin iter sounds i end iter iter gt second gt release sounds i clear Release system system gt release Loading songs and sound effects The loading portion of the manager is very similar to what we did in the last chapter The public methods LoadsFx and LoadSong delegate their work to the private Load method which does the actual loading process The only difference is that the Load method needs to use the correct sound map and mode from the arrays based on the value of the first parameter void AudioManager LoadSFX const std string amp path Load CATEGORY SFX path void AudioManager LoadSong const std string amp path Load CATEGORY SONG path 34 Chapter 3 void AudioManager Load Category type const std string amp path if sounds type find path sounds type end return FMOD Sound sound system gt createSound path c str modes type 0 amp sound sounds type insert std make_pair path sound Playing and stopping sound effects Sou
10. In the following example we have added a second parameter to the event which modifies the pitch of the first layer and the volume of the second layer 64 Chapter 5 0 400 0 600 0 800 Subroarine Environ Finally by right clicking on any sound inside a multi track event we can access some sound instance properties that are not available elsewhere Among those properties there is an auto pitch feature which behaves like adding a pitch effect to that sound and controlling it based on a parameter but is simpler to use This feature is useful when trying to simulate the sound of a car engine Length Start Mode Loop Mode Immediate Loop and cutoff Loop Count Autopitch Enabled Autopitch Parameter Event primary parameter Autopitch Reference Autopitch at Min Fine Tune length S S boop Count e Autopiteh Enabled No S Examples of multi track events Here are some ideas of how we can use multi track events to provide a more interactive and dynamic game audio experience in our games Many of these ideas build upon the ones discussed earlier for simple events 65 Intelligent Audio Creating an interactive footsteps sound loop One of the simple event examples from the previous section described how to generate a looping footsteps sound However that sound was only useful for a specific walking speed and for a specific surface Using multi track events we can create a single sound event that contains foo
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12. sine wave phase 32767 0 volume Mix sample with output data i PCM16 data i value data i 1 PCM16 data i 1 value Increment phase phase increment Wrap phase to the 0 2PI range if phase gt TWO PI phase TWO PI The actual audio data is generated by the sine_wave method highlighted in the previous code All that this method does is call the standard sin function on the phase value and return the result We can easily swap this method with any of the following implementations depending on the type of sound wave that we want to play double sine wave double phase return sin phase double square wave double phase return phase lt PI 1 0 1 0 double downward sawtooth wave double phase return 1 0 2 0 phase TWO PI double upward sawtooth wave double phase return 2 0 phase TWO PI 1 0 94 Chapter 6 double triangle wave double phase double result upward sawtooth wave phase if result lt 0 0 result result return 2 0 result 0 5 Summary In this chapter we have seen how to work directly with the bits and bytes of audio data how to load the audio data from a canonical WAV file how to play and control audio data using only low level operations how to implement a simple delay effect and how to synthesize some basic sound waves a p95 ad 7WNYNT Symbols 3D audio 42 fdp extension 56
13. the merchants the music changes very smoothly into the corresponding variation while retaining the correct relative positioning within the theme The horizontal approach re sequencing In this approach the music moves or jumps between different sections depending on the events of the game This usually requires splitting the music into segments so that the game can transition between them When the system is not transitioning between segments it keeps looping the current segment and the music continues playing indefinitely 68 Chapter 5 Information about the tempo and time signature of the music is frequently required so that the audio system can synchronize transitions to beats or measures of the song to provide a more musical experience The interactive music system in the FMOD Designer is capable of creating interactive music sequences in this fashion A classic example of interactive music using the horizontal approach is the song A pirate I was meant to be in Monkey Island 3 where the player can actually select in real time what verse of the song the characters will sing next The song waits in a loop while the player makes his choice and transitions gracefully afterwards Calling sound events from the game code In order to test our FMOD Designer project in a game we must first build the project by selecting the Build from the Project menu or pressing Ctrl B This process will generate the fev and fsb files t
14. 0 040E 040E J FMOD VECTOR up 0 0f 1 0 0 0f system gt set3DListenerAttributes 0 amp pos amp vel amp forward amp up This is very similar to setting up the attributes for an audio source except for the added orientation The orientation is specified as a pair of normalized perpendicular vectors pointing in the up and forward directions of the listener which you will typically get from your camera object or from the view transformation matrix The first parameter is an index that identifies the audio listener By default there is only one audio listener in the scene so we use the value of 0 If we need more than one audio listener we can use the set3DNumListeners method of the system object to increase that number 45 3D Audio Integration with a game There are several ways to approach this problem depending on the architecture used by the game engine but in general the process is to assign an audio source to each game object that can emit a sound and assign an audio listener to the camera object Then in the update phase of our game loop every time we change the position velocity or orientation of a game object or camera we must follow it up with an update to the corresponding audio structures Finally at the end of the update phase we update the audio system which processes all the changes made to the sources and listeners and updates the simulation accordingly Reverb Positional audio with
15. DSP effects are algorithms that modify the audio data to achieve a certain goal Now we will see an example of how to implement a simple delay effect The way a basic delay effect works is to keep a separate buffer of data and store the audio data that has already played in it The size of the buffer determines how long it takes between the original sound and its echo plays Then we simply need to mix the audio data that is playing with a portion of the old signal that was stored in the buffer which produces a delay Let us examine the following MyDelay class definition which encapsulates the effect class MyDelay pu ublig MyDelay float time float decay MyDelay void WriteSoundData PCM16 data int count private PCM16 buffer int size int position float decay 90 Chapter 6 The MyDelay class constructor takes two parameters time and decay The first parameter controls how many seconds it takes between the sound and the first echo occurs The second parameter controls how much energy is lost during each echo The class stores a buffer of PCM16 samples which we initialize in the constructor so that it can store the equivalent of time seconds of data at a sampling rate of 44100 Hz This buffer starts completely filled with zeros It also contains a position variable that will be used to cycle through the buffer MyDelay MyDelay float time float decay position 0 decay decay Size
16. FMOD System system FMOD System Create amp system Notice that the function returns the system object through a parameter You will see this pattern every time one of the FMOD functions needs to return a value because they all reserve the regular return value for an error code We will discuss error checking in a bit but for now let us get the audio engine up and running Now that we have a system object instantiated we also need to initialize it by calling the init method system gt init 100 FMOD INIT NORMAL 0 The first parameter specifies the maximum number of channels to allocate This controls how many sounds you are able to play simultaneously You can choose any number for this parameter because the system performs some clever priority management behind the scenes and distributes the channels using the available resources The second and third parameters customize the initialization process and you can usually leave them as shown in the example Many features that we will use work properly only if we update the system object every frame This is done by calling the update method from inside your game loop system gt update You should also remember to shutdown the system object before your game ends so that it can dispose of all resources This is done by calling the release method system gt release 15 Audio Playback Loading and streaming audio files One of the greatest things about
17. FMOD Designer how we can also apply some of these concepts to music and play sound events created in the FMOD Designer from our applications 71 Low level Audio We have now reached the final chapter of this book So far we have worked with audio at many different levels of complexity and abstraction using both low level and high level audio engines These audio engines provide an invaluable help to the developers and we should definitely use them whenever possible With their help we have loaded and played audio files learnt how to control sound parameters simulated sound in 3D environments and created complex multi layered interactive sounds In this chapter however we will pretend that these audio engines do not exist and work with nothing more than the bits and bytes that represent sound in a computer We will then re implement in a simplified form many of the features that FMOD takes care for us We will also take a brief look at sound synthesis which is the act of generating sound using mathematical formulas instead of relying on recorded audio The purpose of this chapter is to further our understanding of how sound works and to gain some insight into many of the features that audio engines implement for us It should also serve as a starting point for those who are looking to implement complex audio features in their games Representing audio data In Chapter 1 Audio Concepts we discussed the most important c
18. FMOD is that you can load virtually any audio file format with a single method call To load an audio file into memory use the createSound method FMOD Sound sound system gt createSound sfx wav FMOD DEFAULT 0 amp sound To stream an audio file from disk without having to store it in memory use the createStream method FMOD Sound stream system gt createStream song ogg FMOD DEFAULT 0 amp stream Both methods take the path of the audio file as the first parameter and return a pointer to an FMOD Sound object through the fourth parameter which you can use to play the sound The paths in the previous examples are relative to the application path If you are running these examples in Visual Studio make sure that you copy the audio files into the output folder for example using a post build event such as xcopy y ProjectDir ogg nS OUEDIE E The choice between loading and streaming is mostly a tradeoff between memory and processing power When you load an audio file all of its data is uncompressed and stored in memory which can take up a lot of space but the computer can play it without much effort Streaming on the other hand barely uses any memory but the computer has to access the disk constantly and decode the audio data on the fly Another difference in FMOD at least is that when you stream a sound you can only have one instance of it playing at any time This limitation exists because the
19. and information on a number of AndEngine functions including illustrations and diagrams for added support and results 2 Learn all about the various aspects of AndEngine with prime and practical examples useful for bringing your ideas to life 3 Improve the performance of past and future game projects with a collection of useful optimization tips CryENGINE 3 Cookbook ISBN 978 1 84969 106 2 Paperback 324 pages Over 90 recipes written by Crytek developers for creating third generation real time games 1 Begin developing your AAA game or simulation by harnessing the power of the award winning CryENGINE3 2 Create entire game worlds using the powerful CryENGINE 3 Sandbox 3 Create your very own customized content for use within the CryENGINE3 with the multiple creation recipes in this book Please check www PacktPub com for information on our titles
20. audio project file that groups all sound events together This means that the game only needs to load this single file to get access to all sound events which is significantly easier than having to load every individual audio file Introducing the FMOD Designer The FMOD Designer is the high level data driven API that complements the FMOD Ex low level engine that we have been using so far It contains two parts e FMOD Designer This is a sound designer tool that allows us to create complex sound events and interactive music for our games from http www fmod org e FMOD Event System This is an application layer that lets us use the content created with the designer within our games comes bundled with FMOD Ex inside the moddesignerapi folder 55 Intelligent Audio The FMOD Designer projects have the fdp extension but to use them inside of a game you must first build them from the Project menu The build process generates a fev file containing all the information for every sound event in the project and one fsb file for each wave bank in the project which is where the audio files are stored The following is a screenshot of the FMOD Designer user interface Fie Cdk Project Audition View Window Heb Events Sound Defs Music Banks rajet mcameles v Language defautt Catagories E examples AdvancedTechniques Car neverdirome E Car lamei wes Aj a PU 0 08 tive 0 WA FeatureDemonstration gt B Key Of stopp
21. category is just a matter of calling the corresponding channel group method void AudioManager SetMasterVolume float volume master gt setVolume volume void AudioManager SetSFXsVolume float volume groups CATEGORY SFX gt setVolume volume void AudioManager SetSongsVolume float volume groups CATEGORY SONG gt setVolume volume 38 Chapter 3 Summary In this chapter we have seen how to control the playback of a sound how to control the volume pitch and panning of a sound how to control multiple sounds at once using channel groups and finally how to apply these features in practical situations such as fading between songs or applying random variations to sound effects 39 www allitebooks com 3D Audio Our perception of sound varies depending on where we are located in relation to its source and on several characteristics of the environment We have already discussed that sound is a mechanical wave which has an origin and needs to travel all the way to our ears before we can hear it Along the way those sound waves interact with the environment such as walls objects or the air itself and begin to change Many of the changes provide valuable cues for our brain to determine the location of the sound or the nature of the environment The following is a list of some of the most important factors that have an impact on sound e Distance The distance between the source of
22. example code files for all Packt books you have purchased from your account at http www packtpub com If you purchased this book elsewhere you can visit http www packtpub com support and register to have the files e mailed directly to you 5 Preface Errata Although we have taken every care to ensure the accuracy of our content mistakes do happen If you find a mistake in one of our books maybe a mistake in the text or the code we would be grateful if you would report this to us By doing so you can save other readers from frustration and help us improve subsequent versions of this book If you find any errata please report them by visiting http www packtpub com submit errata selecting your book clicking on the errata submission form link and entering the details of your errata Once your errata are verified your submission will be accepted and the errata will be uploaded on our website or added to any list of existing errata under the Errata section of that title Any existing errata can be viewed by selecting your title from http www packtpub com support Piracy Piracy of copyright material on the Internet is an ongoing problem across all media At Packt we take the protection of our copyright and licenses very seriously If you come across any illegal copies of our works in any form on the Internet please provide us with the location address or website name immediately so that we can pursue a remedy P
23. its attenuation speaker placement and Doppler effect comprises the most fundamental level of 3D audio Now we will cover some advanced techniques that we can use on top of positional audio to provide a more complete simulation of how sounds interact with the environment One of those techniques is called reverberation or reverb Reverb is the capability of sound to persist in a particular space for some time after the original sound has stopped We can think of reverb as a succession of echoes with very little time in between them Reverb occurs because most audio sources project sound in several directions at once Some of those sound waves reach our ears directly in the shortest path possible Others however head in different directions and reflect off various surfaces such as walls before finally reaching our ears These reflected sound waves take longer to reach our ears than the direct sound waves and become quieter with every bounce they make The combination of all the reflected sound waves creates the effect of reverb 46 Chapter 4 Simulating reverb in a game can enhance the realism of a scene because it provides strong cues about the size and nature of the environment For example an empty cathedral with large reflective walls will usually result in a lot of reverb On the other hand an outdoor location with no walls will have virtually no reverb We can also infer the size of a room from the duration of the reverb
24. most sounds that you hear are actually a combination of several different frequencies 1st Cycle 2st Cycle 1 second Lower Pitch Higher Pitch Frequency 2 Hz Frequency 4 Hz 8 Chapter 1 Analog and digital audio Now that we know what sound is let us turn our thoughts towards recording the sound and storing it on a computer The first step in this process is to convert the sound wave into an electrical signal When we use a continuous signal to represent another signal of a different quantity we call it an analog signal or in the case of a sound wave an analog audio signal You are probably already familiar with the devices that perform this conversion e Microphones These are devices that convert sound waves into electrical signals e Speakers These are devices that convert electrical signals into sound waves Analog signals have many uses but most computers cannot work with them directly Computers can only operate on sequences of discrete binary numbers also known as digital signals We need to convert the analog signal recorded by the microphone into a digital signal that is digital audio before the computer can understand it The most common method used to represent analog signals digitally is pulse code modulation PCM The general idea of PCM is to sample or measure the amplitude of the analog signal at fixed time intervals and store the results as an array of numbers called samples Since the origina
25. problem by using a high level audio engine These engines usually provide an external tool that the sound designer can use to create complex sounds independently from a programmer and store them as sound events Then regardless of the complexity of the sound the programmer can easily trigger it from the game usually by writing the name of the event Intelligent Audio The main difficulty in covering this topic is that there are several high level audio engines available and each of them has its own set of features and philosophy Using these tools we can perform things such as generative audio generating audio at runtime from a set of sound samples and rules or adaptive music music that changes depending on game events To simplify the terminology we will be using the term intelligent audio to encompass all situations where a sound can have complex behavior attached to it In this chapter we will work with the FMOD Designer tool and see some of the interesting stuff that we can do with it A detailed coverage of the tool would be impossible given the limited scope of the book but it should be enough to give you some ideas and to get you started For more information the FMOD Designer tool ships with a user manual that is over 400 pages long and a sample project with many examples Audio files versus sound events Before installing the FMOD Designer tool let us start by really understanding the difference between treating each aud
26. propagate away from the objects in the form of sound waves Our ears are capable of detecting incoming sound waves and converting them into nerve signals that our brain interprets as sound One way to visualize sound is to draw a graph of the variations in the atmospheric pressure at each moment in time However understanding how those graphs relate to what we hear can be extremely complex For that reason we usually start by studying the simplest type of wave the sine wave Audio Concepts The sine wave is interesting for educational purposes because we can easily identify two of the main properties of sound from it volume and pitch Most audio libraries allow us to control both of these properties for any sounds that we play Volume This property corresponds to how loud or quiet the sound is It depends directly on the amplitude or the height of the sound wave as measured on the vertical axis The main unit of volume is the decibel dB but most audio libraries use a scale between zero silence and one full volume Pressure Amplitude i Amplitude Lower Volume Higher Volume Pitch This property determines how high or low the sound is It depends on the frequency of the sound wave which is the number of times that it repeats every second The unit of frequency is the hertz Hz Two things that you should know about frequency are that the human ear can only hear frequencies within the 20 Hz and 20 000 Hz range and that
27. sampleRate channels bytesPerSample durationInSeconds info length 44100 2 sizeof signed short 5 Number of samples we will be submitting at a time A smaller value results in less latency between operations but if it is too small we get problems in the sound In this case we will aim for a latency of 100ms i e sampleRate durationInSeconds 44100 0 1 4410 75 Low level Audio info decodebuffersize 4410 Specify the callback function that will provide the audio data info pcmreadcallback WriteSoundData Next we create a looping streaming sound specifying the FMOD_OPENUSER mode and passing it the sound info structure to the third parameter of createStream We can then begin playing the sound as normal Create a looping stream with FMOD OPENUSER and the info we filled FMOD Sound sound FMOD MODE mode FMOD LOOP NORMAL FMOD OPENUSER system gt createStream 0 mode amp info amp sound system gt playSound FMOD CHANNEL FREE sound false 0 As long as the sound is playing the audio engine invokes our callback function periodically to get the data it requires The callback function must follow a certain signature that takes three parameters a reference to the sound object that we created an array for us to write the audio data into and the total number of bytes that we should write to the data array It should also return FMOD_OK at the end The data array is defined
28. scount if Loop 4 position 0 else Stop 3 return 86 Chapter 6 PCM16 value PCM16 sound sdatal int position volume data i value data i 1 value position pitch However the truncation from the cast can introduce distortion into the signal For example if the position is advancing at a slower pace than normal it will have many values that are between whole numbers but because of the truncation from the cast we will get the same value written multiple times to the output instead of a flowing sound wave A better approach is to use linear interpolation or another type of interpolation to calculate a value for the sample that takes the surrounding values and the fractional portion of the position into consideration For example using linear interpolation if the position was 2 25 instead of outputting the value of data 2 we would output a mix of 75 percent of the value of data 2 with 25 percent of the value of data 3 instead Changing panning There are many different approaches to implement stereo panning of a sound In this section we will cover a simple approach that works just by modifying the volumes of the left and right channels independently Before actually doing any calculations let us prepare the class for panning by adding two private variables leftGain and rightGain to store the volumes of each channel private float leftGain float rightGain
29. since sound waves have to travel longer in a large room than in a small room Reverb in FMOD If we are already using positional audio in our scene adding reverb in FMOD requires only a few extra lines of code Creating a reverb object First we need to create an FMOD Reverb object using the createReverb method FMOD Reverb reverb system gt createReverb amp reverb This creates a reverb zone that automatically applies reverb to every sound that a listener can hear when standing inside that zone You can safely create more than one reverb zone simultaneously as FMOD automatically combines their effects To disable a reverb zone you can use the setActive method Alternatively if you do not need that zone any more you can destroy it permanently with the release method reverb gt setActive false Disable temporarily reverb gt release Destroy reverb Setting reverb properties A reverb has many properties to customize its behavior These properties are defined inside the FMOD_REVERB_ PROPERTIES structure and can be applied to the reverb object using the set Properties method Fortunately FMOD also provides a set of presets that you can use directly such as FMOD_PRESET_CONCERTHALL FMOD REVERB PROPERTIES properties FMOD PRESET CONCERTHALL reverb gt setProperties amp properties 47 3D Audio Setting reverb position and radius We can specify the position and range of the reverb using
30. to access PacktLib today and view nine entirely free books Simply use your login credentials for immediate access www allitebooks com Table of Contents Preface 1 Chapter 1 Audio Concepts 7 Sound waves 7 Analog and digital audio 9 Multi channel audio 11 Audio file formats 11 Summary 12 Chapter 2 Audio Playback 13 Understanding FMOD 13 Installing FMOD Ex Programmer s API 14 Creating and managing the audio system 15 Loading and streaming audio files 16 Playing sounds 17 Checking for errors 18 Project 1 building a simple audio manager 19 Class definition 19 Initialization and destruction 21 Loading or streaming sounds 22 Playing sounds 22 A note about the code samples 23 Summary 24 Chapter 3 Audio Control 25 The channel handle 25 Controlling the playback 26 Controlling the volume 27 Controlling the pitch 27 Controlling the panning 29 Grouping channels together 30 www allitebooks com Table of Contents Controlling groups of channels 31 Project 2 improving the audio manager 32 Class definition 32 Initialization and destruction 33 Loading songs and sound effects 34 Playing and stopping sound effects 35 Playing and stopping songs 36 Controlling the master volume of each category 38 Summary 39 Chapter 4 3D Audio 41 Positional audio 42 Positional audio in FMOD 43 Creating an audio source 43 Setting the audio source s position and velocity 43 Setting the audio source s direction 44 Setting the audio sourc
31. unsigned int U32 typedef unsigned short U16 After deciding what format to use we need to create an array to hold all of the audio samples The size of the array depends directly on the sampling rate of the sound we want to store its duration in seconds and the number of channels being used according to the following formula count sampling rate duration channels For example assuming a sampling rate of 44100 Hz we could create an array to store exactly 1 second of mono audio data like the following 1 second of audio data at 44100 Hz Mono count 44100 Hz 1 second 1 channel PCM16 data 44100 If we wanted to store a stereo signal instead we would need to store twice that amount of information and the same idea applies to higher amounts of channels Remember that the most common way to represent stereo audio data is to interleave samples left and right in the same array 1 second of audio data at 44100 Hz Stereo Cate 0 left data 1 right dave Lert etc count 44100 Hz 1 second 2 channels PCM16 data 88200 74 Chapter 6 Playing audio data We need a way to submit the audio data to the sound card so that we can hear the resulting sound We could use a very low level audio API such as PortAudio which provides the bare minimum functionality required to communicate with an audio device However FMOD is also perfectly capable of handling this task and since we have been
32. using it so far there is little benefit in changing to a different API now Therefore we will use FMOD once again but only as bridge between the application and the hardware and our code will handle all of the processing The way FMOD allows us to play user created audio data is by first creating a sound with the FMOD_OPENUSER flag and specifying a callback function that will provide the audio data to the sound We must create and fill a FMOD_CREATESOUNDEXINFO structure with a few details regarding the audio data that we will be submitting such as the sampling rate format and number of channels as well as a pointer to the function that will provide the data itself For all of our examples we will work with a sampling rate of 44100 Hz use the 16 bit PCM format and have two channels stereo Read the comments for more information about each attribute Create and initialize a sound info structure FMOD CREATESOUNDEXINFO info memset amp info O sizeof FMOD CREATESOUNDEXINF O info cbsize sizeof FMOD CREATESOUNDEXINFO Specify sampling rate format and number of channels to use In this case 44100 Hz signed 16 bit PCM Stereo info defaultfrequency 44100 info format FMOD SOUND FORMAT PCM16 info numchannels 2 Size of the entire sound in bytes Since the sound will be looping it does not need to be too long In this example we will be using the equivalent of a 5 seconds sound i e
33. FTSIZE 4096 Now only the speed will change channel gt addDSP dsp 0 Example 2 simple radio effect You can also combine multiple effects to achieve behaviors that are more complicated For example here is a rudimentary radio effect simulation which works by applying a distortion and a high pass filter to the sound FMOD DSP distortion system gt createDSPByType FMOD DSP TYPE DISTORTION amp distortion distortion gt setParameter FMOD DSP DISTORTION LEVEL 0 85f FMOD DSP highpass system gt createDSPByType FMOD DSP TYPE HIGHPASS amp highpass highpass gt setParameter FMOD DSP HIGHPASS CUTOFF 2000 0f channel gt addDSP distortion 0 channel gt addDSP highpass 0 The distortion simulates the loss of information that often occurs when transmitting analog signals and the high pass filter makes the sound thinner by getting rid of the lower frequencies Summary In this chapter we have seen how to simulate sound coming from specific locations in the environment how to simulate reverb from reflected sound waves how to simulate obstruction and occlusion from obstacles and finally how to apply DSP effects to sounds 52 Intelligent Audio Up to this point we have played sounds in a very linear fashion we load an audio file from a disk and play it when needed optionally controlling some of its parameters during playback Even when we used advanced features such as 3D audio there wa
34. a large number of singing birds Using a multi track event we can easily extend the ambient track to contain other layer of sounds For example we could add a layer with the sound of the wind looping in the background and layers for other types of animal cries probably occurring at different rates than the bird sounds If we wanted to simulate a cave within the forest we could create a parameter to control the location of the character and add an occlusion effect to every layer that is only active for a certain range of values Additionally we could create a parameter to specify the time of the day and play different sounds depending on its value such as removing the sounds of the birds at night and bringing some cricket sounds in Interactive MUSIC In the same way that we can create complex sound effects that change depending on the events of the game it is also possible to do the same for the game s background music This allows the music to adapt to the circumstances for example to convey the correct emotion for the moment or provide a sense of tension when danger draws near 67 Intelligent Audio Music that is played in a non linear fashion like this is known as interactive music if the player directly controls the changes or adaptive music if the music reacts to the game environment but not necessarily to the player There are two main approaches to creating interactive music The vertical approach re orchestrat
35. al channel group called the master channel group where every channel is placed every time you play a sound You can get a reference to the master channel group by calling the getMasterChannelGroup method of the system object FMOD ChannelGroup masterGroup system gt getMasterChannelGroup amp masterGroup 30 Chapter 3 A good way to organize sounds in our games is to create a channel group for each category of sounds and add all channel groups to the master channel group This way we have control over individual categories but we also have a way to control all sounds at once Controlling groups of channels Most operations supported by channel groups are the same that we have seen already for individual channels In particular we can stop pause or mute all channels in a group and control their volume and pitch The syntax for these operations is the same as before except for pitch which is done through a set Pitch method that instead of a frequency takes any value between 0 and 10 and multiplies it by the current frequency Calls stop on all channels in the group channelGroup gt stop Mute or pause all channels channelGroup gt setMute true channelGroup gt setPaused true Halve the volume of all sounds in the group channelGroup gt setVolume 0 5 Double the frequency of all sounds in the group channelGroup gt setPitch 2 0 All of these changes propagate down the channel grou
36. anning One of the simplest approaches is to use linear panning where each channel starts at 0 percent volume in one side and increases linearly to 100 percent on the other side while being at 50 percent in the middle Here is an implementation of linear panning Linear panning void MyChannel UpdatePan float position pan 0 5f leftGain 0 5f position rightGain position 0 5f 88 Chapter 6 Another approach which usually yields a smoother transition when panning is to use constant power panning where the volume of each channel follows a circular curve with the volume of each channel being roughly 71 percent in the middle We have already discussed constant power panning before since it is the type of panning used by FMOD for panning mono sounds Without going into details about the math involved here is an implementation of constant power panning include lt math h gt define PI 4 0 78539816339 PI 4 define SQRT2 2 0 70710678118 JI SORT 2 2 Constant power panning void MyChannel UpdatePan double angle pan PI 4 leftGain float SORT2 2 cos angle sin angle rightGain float SQRT2_ 2 cos angle sin angle Mixing multiple sounds So far we have only been playing one sound at a time but it is quite easy to extend what we are doing to play multiple sounds at once The act of combining multiple sounds into a single output is known as audio mixing and
37. ata int count if sound 0 paused return for int i 0 i count i 2 4 if position gt sound gt count Stop 3 return PCM16 value sound gt data position data i value data i 1 value position 83 Low level Audio Looping a sound The next feature that we will implement is the ability to endlessly make a sound loop Like the ability to pause a sound this is also quite trivial to implement We begin by repeating everything that we did for pausing but for looping instead public bool GetLoop const return loop void SetLoop bool value loop value private bool loop Inside the WriteSoundData method in the part where we used to detect if the sound had already reached the end we first check if the loop variable is set to true and if that is the case we set the position back to the beginning instead of stopping the sound void MyChannel WriteSoundData PCM16 data int count if sound 0 paused return f r Ame i 0p 1i lt count i 2 2 4 if position gt sound gt count if loop position 0 else Stop J return PCM16 value sound gt data position data i value data i 1 value position Changing volume The next few features that we will implement involve modifying the values that are sent to the output Changing the volume of a sound is probably the simplest of them as it only requires a multiplication 84
38. ation will always work without errors However in a real scenario there is room for a lot to go wrong For example we could try to load an audio file that does not exist In order to report errors every function and method in FMOD has a return value of type FMOD_RESULT which will only be equal to FMOD_OK if everything went right It is up to the user to check this value and react accordingly FMOD RESULT result system gt init 100 FMOD INIT NORMAL 0 if result FMOD OK There was an error do something about it For starters it would be useful to know what the error was However since FMOD_RESULT is an enumeration you will only see a number if you try to print it Fortunately there is a function called FMOD_ErrorString inside the fmod_errors h header file which will give you a complete description of the error You might also want to create a helper function to simplify the error checking process For instance the following function will check for errors print a description of the error to the standard output and exit the application include lt iostream gt include lt fmod errors h gt void ExitOnError FMOD RESULT result if result FMOD OK std scout lt lt FMOD ErrorsString result lt lt std endl exit 1 You could then use that function to check for any critical errors that should cause the application to abort ExitOnError system gt init 100 FMOD INIT NORMAL 0 j T
39. audio system creating 15 managing 15 B breaking glass sound effect creating 61 C car engine sound simulating 66 ChangeSemitone method 35 channel groups controlling 31 channel handle 25 channels erouping 30 chorus effect 50 chunks WAV files Data subchunk 77 Format subchunk 77 RIFF 77 complex ambient track of forest creating 67 compressor effect 50 constant power panning 89 Core Audio 13 createChannelGroup method 30 createDSPByType method 51 createSound method 16 createStream method 16 cues 56 D Data subchunk 77 default ambient reverb setting 48 delay effect 50 implementing 90 91 digital signal processing See DSP effect digital signals 9 DirectSound 13 distortion effect 50 Doppler effect 41 DSP effect 50 90 DSP effect types chorus 50 compressor 50 delay 50 distortion 50 echo 50 flanger 50 high pass filter 50 low pass filter 50 noise removal 50 normalize 50 parametric EQ 50 pitch shift 50 E echo effect 50 effects FMOD about 51 simple radio effect 52 time stretching 51 F fa ade design pattern 19 FLAC 12 flanger effect 50 FMOD about 13 75 advantages 14 effects 51 obstruction simulating 49 occlusion simulating 49 positional audio 43 98 FMOD 2D mode 17 FMOD _3D mode 17 FMOD Channel class 43 FMOD_CREATESOUNDEXINFO structure 75 FMOD Designer tool about 54 55 URL for downloading 55 FMOD Event System 55 FMOD Ex low level engine 55 FMOD Ex Programm
40. be in the correct format instead of the void provided to the audio callback The count also refers to the number of samples in the array not the number of bytes There are comments in the code explaining what each line is doing void MyChannel WriteSoundData PCM16 data int count If there is no sound assigned to the channel do nothing if sound 0 return We need to write count samples to the data array Since output is stereo it is easier to advance in pairs 81 Low level Audio for int i s 0p i Count a 4S2 4 If we have reached the end of the sound stop and return if position gt sound scount Stop 7 return Read value from the sound data at the current position PCM16 value sound gt data position Write value to both the left and right channels data i value data i 1 value Advance the position by one sample position Using this class our audio callback becomes a lot simpler as we can delegate most of the work to the WriteSoundData method of the channel In the following example there is a single channel object so we can only play one sound at a time but later we will see how easy it is to add support for multiple sounds as well as several other features MyChannel channel FMOD RESULT F CALLBACK WriteSoundData FMOD SOUND sound void data unsigned int length Clear output memset data 0 length Get data in the correct forma
41. bject We should always release the sounds we create regardless of the audio system also being released sound gt release Playing sounds With the sounds loaded into memory or prepared for streaming all that is left is telling the system to play them using the playSound method FMOD Channel channel system gt playSound FMOD CHANNEL FREE sound false amp channel The first parameter selects in which channel the sound will play You should usually let FMOD handle it automatically by passing FMOD_CHANNEL_FREE as the parameter The second parameter is a pointer to the FMOD Sound object that you want to play The third parameter controls whether the sound should start in a paused state giving you a chance to modify some of its properties without the changes being audible If you set this to true you will also need to use the next parameter so that you can unpause it later The fourth parameter is an output parameter that returns a pointer to the FMOD Channel object in which the sound will play You can use this handle to control the sound in multiple ways which will be the main topic of the next chapter You can ignore this last parameter if you do not need any control over the sound and simply pass in 0 in its place This can be useful for non lopping one shot sounds system gt playSound FMOD CHANNEL FREE sound false 0 17 Audio Playback Checking for errors So far we have assumed that every oper
42. by a pointer to void void because as we discussed earlier there are many different formats for the data to be in It is up to us to cast the data array to the correct format Since we created the sound with FMOD_SOUND_ FORMAT _PCM16 we have to cast the data array toa signed short first Another important detail is that the length parameter specifies the amount of data to write to the array in bytes but each of our samples is a signed short which occupy 2 bytes each Therefore we should make sure to write no more than length 2 samples to the data array Here is an example of a callback function which outputs silence by filling the entire audio buffer with zeros Not very interesting but it should serve as a good starting point FMOD RESULT F CALLBACK WriteSoundData FMOD SOUND sound void data unsigned int length Cast data pointer to the appropriate format in this case PCM16 PCM16 pcmData PCM16 data Calculate how many samples can fit in the data array In this case since each sample has 2 bytes we divide fy Length by 2 int pcmDataCount length 2 Output 0 in every sample 76 Chapter 6 for int i 0 i lt pemDataCount i pemData i 0 return FMOD OK Loading a sound The most common way to get audio data is to read it from an audio file However as we have seen before there are many different audio file formats and reading the audio data out of them is usually a
43. can use it to set the position and velocity of the audio source with the set3DAttributes method FMOD VECTOR position 3 0f 4 0f 2 0f EMOD VECTOR velocity 1 0f 0 0f 0 0 channel gt set3DAttributes amp position amp velocity We will typically set these values once when creating the audio source and update them every frame or every time the game object associated with the audio source changes its position or velocity 43 3D Audio By default the position is defined in meters and the velocity is defined in meters per second as we would typically see on a physics engine We can change this scale by setting a different distancefactor parameter in the System set3DSettings method Note that simply subtracting an object s position by its position on the previous frame does not yield a velocity in meters per second as required If we need to use this method for example because we do not know the actual velocity of the object we have to multiply this delta by the time elapsed since the previous frame first in seconds FMOD VECTOR velocity velocity x position x lastPosition x elapsed velocity y position y lastPosition y elapsed velocity z position z lastPosition z elapsed Setting the audio source s direction By default every sound source is omnidirectional which means that the sound is emitted equally in every direction We can give a sound source a direction by defining a p
44. cted sound waves are not affected Occlusion occurs when the source and listener are in different environments and all the sound needs to go through an obstacle such as a wall before reaching the listener In this situation both direct and reflected sound waves are attenuated and filtered 48 Chapter 4 The filter applied to the obstructed or occluded sound waves is usually a low pass filter which attenuates the higher frequencies resulting in a muffled sound Obstruction Occlusion Obstruction and occlusion in FMOD We can simulate obstruction and occlusion in FMOD using the built in geometry engine This only works if we already have our audio sources and listeners set up Afterwards we need to create geometry objects to represent the obstacles in our environment The easiest way to create these objects is to start from a 3D triangle mesh representation of our obstacle Then we create an instance of FMOD Geometry with enough space to store all of our triangles and vertices using the createGeometry method FMOD Geometry geometry system gt createGeometry numTriangles numVertices amp geometry Next for each triangle in our mesh we add a new polygon to the geometry object using the addPolygon method The first two parameters control the amount of obstruction and occlusion to perform The third parameter decides if the polygon should be double sided The fourth parameter is the number of vertices in the polyg
45. d and set to loop Only one song can be playing at any time Transitions between songs are handled smoothly by the audio manager with volume fades Each game has its own needs so you might want to create more categories such as one for speech or ambient tracks Class definition Once again let us start with a listing of the class definition include lt string gt include lt map gt include lt fmod hpp gt class AudioManager public AudioManager AudioManager void Update float elapsed void LoadSFX const std string amp path void LoadSong const std string amp path void PlaySFX const std string amp path float minVolume float maxVolume float minPitch float maxPitch void PlaySong const std string amp path void StopSFXs void StopSongs 32 Chapter 3 void SetMasterVolume float volume void SetSFXsVolume float volume void SetSongsVolume float volume private typedef std map lt std string FMOD Sound gt SoundMap enum Category CATEGORY SFX CATEGORY SONG CATEGORY COUNT void Load Category type const std string amp path FMOD System system FMOD ChannelGroup master FMOD ChannelGroup groups CATEGORY COUNT SoundMap sounds CATEGORY COUNT FMOD MODE modes CATEGORY COUNT FMOD Channel currentSong std string currentSongPath std string nextSongPath enum FadeState FADE NONE FADE IN FADE OUT FadeState fade
46. e method 85 93 100 SFML Simple and Fast Multimedia Library 2 0 about 23 URL 23 SimpleAudioManager class 19 simple events about 56 57 creating 57 examples 60 61 functionalities 57 simple radio effect 52 sine wave 7 sine_wave method 94 sin function 94 songs 32 sound about 7 loading 22 77 79 looping 84 pausing 83 pitch changing 86 playing 17 80 83 simulating of car engine 66 streaming 22 synthesizing 92 94 volume changing 84 sound defs 56 sound effects SFXs 32 sound events calling from game code 69 70 versus audio files 54 55 sound events FMOD multi track 56 61 64 simple 56 59 sound factors direction 41 distance 41 movement 41 obstacles 41 room 41 sound synthesis 92 sound waves 7 speakers 9 Standard Template Library STL 20 stop method 26 StopSongs method 37 Stream method 22 System set3DSettings method 44 U uncompressed audio files 11 update method 15 UpdatePan method 88 V vertical approach re orchestration 68 volume changing of sound 84 controlling 27 volume property 8 W WAV 11 WMA 12 WriteSoundData method 81 82 86 Wwise 13 101 PAC KT Thank you for buying puatisuing Getting Started with C Audio Programming for Game Development About Packt Publishing Packt pronounced packed published its first book Mastering phpMyAdmin for Effective MySQL Management in April 2004 and subsequently continued to specialize in publishing
47. e s range 44 Setting the audio listener s properties 45 Integration with a game 46 Reverb 46 Reverb in FMOD 47 Creating a reverb object 47 Setting reverb properties 47 Setting reverb position and radius 48 Setting the default ambient reverb 48 Obstruction and occlusion 48 Obstruction and occlusion in FMOD 49 Effects 50 Effects in FMOD 51 Example 1 time stretching 51 Example 2 simple radio effect 52 Summary 52 Chapter 5 Intelligent Audio 53 Audio files versus sound events 54 Introducing the FMOD Designer 55 Simple events 57 Examples of simple events 60 Avoiding repetitive sound effects 60 Creating a footsteps sound loop 60 Creating a breaking glass sound effect 61 Creating an ambient track of singing birds 61 i www allitebooks com Table of Contents Multi track events 61 Examples of multi track events 65 Creating an interactive footsteps sound loop 66 Simulating the sound of a car engine 66 Creating a complex ambient track of a forest 67 Interactive music 67 The vertical approach re orchestration 68 The horizontal approach re sequencing 68 Calling sound events from the game code 69 Summary 71 Chapter 6 Low level Audio 73 Representing audio data 73 Playing audio data 75 Loading a sound 77 Playing a sound 80 Pausing a sound 83 Looping a sound 84 Changing volume 84 Changing pitch 86 Changing panning 87 Mixing multiple sounds 89 Implementing a delay effect 90 Synthesizing a sound 92 Summary 95 Index 97
48. e the data is stored in its original state normally PCM This means that their data is already prepared for playback without any further processing The downside is that they take up a lot of space on disc approximately 10 MB for one minute of audio For example WAV and AIFF 11 Audio Concepts e Lossless compression These are audio files where the data is encoded using compression algorithms that only perform reversible changes so that no information is permanently lost These files can be up to half the size of the uncompressed formats but need the computer to decode them before playback For example FLAC and APE e Lossy compression These are the audio files where the data is encoded using compression algorithms where some loss of the information is acceptable These algorithms use heuristics to determine which parts of the data are less likely to be audible in order to discard them File sizes can be as small as 10 percent of the original size although sound quality can suffer considerably if the compression is too strong For example MP3 WMA and OGG Sequenced music There are some formats that do not fit into any of the earlier mentioned categories For example MIDI files only store information about how the music should be played but do not contain any sound data leaving it to the computers to decide how they should be interpreted For this reason they are extremely small but sound quality is limited and varies
49. eating Loop mode 59 Successive Loop mode 59 Playlist Behaviors about 58 Random option 58 Sequential option 58 Shuffle option 58 Play method 22 81 83 PlaySFX method 35 PlaySong method 36 playSound method 17 25 PortAudio 13 positional audio 42 43 positional audio in FMOD audio listener properties setting 45 audio source creating 43 audio source direction setting 44 audio source position setting 43 44 audio source range setting 44 audio source velocity setting 43 44 using 43 pow function 28 properties sound pitch 8 volume 8 pulse code modulation See PCM Q quantization 9 R RandomBetween method 35 release method 15 repetitive sound effects avoiding 60 reverb about 46 position setting 48 properties setting 47 radius setting 48 simulating in game 47 reverberation See reverb reverb in FMOD default ambient reverb setting 48 radius setting 48 reverb object creating 47 reverb position setting 48 reverb properties setting 47 reverb object creating 47 RIFF chunk 77 rolloff model 45 S sampled audio bit depth 10 sampling rate 10 sequenced music 12 set3DConeOrientation method 44 set3DConeSettings method 44 setChannelGroup method 30 setFrequency method 27 SetFrequency method 93 setInputChannelMix method 27 setLoopCount method 27 setMute method 27 setPan method 29 setPaused method 26 setPitch method 31 setPosition method 26 setVolume method 27 SetVolum
50. ed CPU0 0G Active O ch Fa I Baas ll BF Randomization d t RO Parameters F t BF Elfocts J _ReverbOrytevel fp P DMa laybac g z 17 SEGRA t te D Events mr aaa Gg Spava TULGE SoustingDistance E Mule hirneasie The most important task of the FMOD Designer is to create sound events There are two types of sound events in FMOD and an interactive music system e Simple events With simple events we can create sounds composed by multiple audio files and play them randomly or sequentially one or several at a time at different rates and with random volume or pitch variation e Miulti track events With multi track events we can combine as many simple events as we need in this case called sound defs organize them into layers apply effects to them control which sound defs should be playing at any given time create custom parameters and link those parameters to any of the properties of the sound or effects e Interactive music With the interactive music system we can create songs called cues composed by multiple segments and have the game transition between them in response to certain events Besides transitions we can also add flourishes to the music which play concurrently and synchronized with the main song 56 Chapter 5 Over the next few sections we will briefly cover the main features and user interface of the first two of these systems as well as some ideas and exa
51. efer to as audio sources in relation to or our ears which we will refer to as the audio listener The first step required to create a 3D audio simulation is to describe every audio source and listener in the environment Note that there is typically only one audio listener in a scene unless we are creating a multiplayer split screen type of game The following figure shows an example of a scene with multiple audio sources and one audio listener in the middle Audio f E Audio Source Source Audio Audio Source Source A Audio zg Listener For each audio source and listener in the scene we store information such as position orientation and velocity Using this information the audio engine produces a 3D audio simulation by modifying all the sounds in real time in several ways e Position The volume of a source decreases and becomes muffled by filtering the sound to attenuate some of the higher frequencies as the distance to the listener increases The formula used to calculate the volume of the sound given a distance is usually controllable by selecting a minimum and maximum distance and a roll off model 42 Chapter 4 e Orientation Depending on the orientation of the listener in relation to each source the audio engine simulates sound direction and position using speaker placement for surround sound systems such as 5 1 or panning for stereo sound systems Audio sources can also be oriented usually by definin
52. epth 10 Chapter 1 Multi channel audio Another aspect that we should talk about is that many audio systems have more than one output By sending different audio signals to separate outputs called channels it is possible to produce the illusion of directionality and space The number of channels on these systems can vary from one mono or two stereo to several more on surround sound systems The PCM format described earlier can store audio for multiple channels at once by interleaving one sample from each channel in the correct order The following figure shows an example of this for a stereo system Left Channel gt Combined Strereo PCM Data Right Channel Besides volume and pitch which we have examined earlier there is another property that you will usually find in every audio library called panning Panning applies to stereo systems and allows you to simulate the position of the sound placing it anywhere between the left and the right channels For positioning in configurations with more than two channels you normally use other advanced features such as 3D sound Audio file formats There are so many different file formats for storing audio on a computer that it is easy to feel overwhelmed at first Thankfully you will only use a couple of them in your games most of the time Audio file formats usually fall into one of the following categories e Uncompressed audio files These are audio files wher
53. er s API about 13 installing 14 15 URL for downloading 14 FMOD_HARDWARE mode 16 FMOD_LOOP_NORMAL mode 16 FMOD_LOOP_OFF mode 16 FMOD_OPENUSER flag 75 FMOD_SOFTWARE mode 16 footsteps sound loop creating 60 Format subchunk 77 G game code sound events calling from 69 70 getFrequency method 28 getMasterChannelGroup method 30 getPaused method 26 H high pass filter effect 50 horizontal approach re sequencing 68 installation FMOD Ex Programmer s API 14 15 interactive footsteps sound loop creating 66 interactive music about 56 67 horizontal approach re sequencing 68 vertical approach re orchestration 68 L Load method 22 LoadOrStream method 22 LoadSFX method 34 LoadSong method 34 logarithmic rolloff 45 lossless compression 12 lossy compression 12 low pass filter effect 50 microphones 9 MIDI files 12 MOD files 12 MP3 format 12 multi channel audio 11 multiple sounds mixing 89 90 multi track events about 56 61 creating 63 examples 65 67 functionalities 61 N noise removal effect 50 normalize effect 50 Nyquist sampling theorem 10 O obstruction about 48 in FMOD 49 occlusion about 48 in FMOD 49 OGG 12 OpenAL 13 P panning about 11 changing 87 88 99 controlling 29 parametric EQ effect 50 PCM 9 pitch changing of sound 86 controlling 27 29 pitch property 8 pitch shift effect 50 playback controlling 26 Playback Modes Granular mode 59 Oneshot mode 59 Rep
54. from system to system There are also hybrid formats such as MOD files also known as module or tracker files which are in many ways similar to MIDI files but also contain any sound data that is required to play them known as instruments Be aware that despite its popularity the MP3 is a patented format and you cannot use it commercially without paying royalties refer to http mp3licensing com for more information For this book we will be using OGG files for long sounds and WAV files for small sound effects Summary In this chapter we have seen that sound is a series of variations in atmospheric pressure travelling in the form of sound waves We also saw that sound waves have properties such as amplitude and frequency which control how loud or high it is and that you can represent a sound wave using electrical signals analog audio and a series of numbers digital audio We learned that when converting an analog signal to a digital signal you need to control the sampling rate and the bit depth Finally we saw that many audio systems have more than one output and that there are many different types of audio file formats 12 Audio Playback In this chapter we will perform two of the most fundamental operations in audio programming loading and playing audio files This might not seem like much but it is already enough to get us started adding audio into our games There are many different audio libraries availab
55. g a sound projection cone with direction and angle information Sound is then attenuated for listeners standing outside the range of the cone e Velocity If the audio source is moving in relation to the listener the pitch of the sound changes increasing as the entities move closer and decreasing as the entities move apart because of the Doppler effect You can hear this effect in the real world for example when an ambulance passes next to you with its siren turned as soon as the ambulance moves past your location there is a sudden drop in the pitch of the siren Positional audio in FMOD Using positional audio in FMOD is not too different from what we have done so far In fact we have already used all the classes required for positional audio on the previous chapters the FMOD Channel class already works as an audio source while the FMOD System class controls all the audio listeners in the scene Let us break down the entire process into steps Creating an audio source The first point that we have to remember is to create our sounds using the FMOD_3D flag otherwise the 3D audio engine will not process them system gt createSound explosion wav FMOD 3D 0 amp sound Then we simply need to play the sounds as usual storing a reference to the channel handle so that we can modify the 3D properties of the sound Setting the audio source s position and velocity Once we play the sound and get back a channel handle we
56. g it sound harsher Low pass filter This effect attenuates all frequencies in the sound above a certain range making the sound muffled High pass filter This effect attenuates all frequencies in the sound below a certain range making the sound thinner Parametric EQ This effect provides complex volume control over all different ranges of frequencies in the sound Delay In this effect the sound plays once and keeps repeating after a certain amount of time until it runs out of energy Echo In this effect a delay with a duration that is long enough for us to perceive as separate sounds Flanger This effect doubles the sound with a very small delay between each instance and varies this delay over time Chorus This effect plays multiple instances of the sound together with small pitch and time variations between them Pitch shift This effect changes the pitch of a sound without altering its playback speed Noise removal This effect silences every value below a certain volume threshold 50 Chapter 4 Effects in FMOD Once again we will only cover the very basics here The easiest way to create a DSP effect in FMOD is to use the createDSPByType method with one of the available DSP types as a parameter check the FMOD documentation for the complete list of types FMOD DSP dsp system gt createDSPByType FMOD DSP TYPE ECHO amp dsp This returns an FMOD DSP object that you can apply to any channel channel gr
57. gle audio file and plays it multiple times with the number of times being controlled by the Play Count parameter e Successive Loop This mode plays multiple audio files in succession picking a new one each time with the number of files to play being controlled by the Loop Count parameter e Granular This mode is similar to the previous mode but allows us to control the time to wait between each file that is played Grain Interval parameter how many files can be playing simultaneously Polyphony parameter and the total amount of files to play before the sound ends Total Grains parameter Playback Options Playback Mode Oneshot Repeating Loop Play Count co a Successive Loop Loop Count O g Queued Sounds 1 8 Granular Grain Interval Polyphony 1 a Total Grains co i Finally there is the Properties pane on the right side of the interface which allows us to control several other properties of the sound event such as most of the 3D audio properties discussed on the previous chapter 59 www allitebooks com Intelligent Audio Examples of simple events Here are some ideas of how we can use simple events to enrich the audio in our games Most of these ideas can be found on the examples project that comes with the FMOD Designer so be sure to look there too Avoiding repetitive sound effects Most games have a few sound effects that are played all the time such as the sound of a character s footsteps o
58. grammer developing a successful career in the area of audio programming for videogames He is responsible for maintaining and improving an existing cross platform end to end audio pipeline as well as working with third party audio middleware such as FMOD and Wwise www allitebooks com www PacktPub com Support files eBooks discount offers and more You might want to visit www Packt Pub com for support files and downloads related to your book Did you know that Packt offers eBook versions of every book published with PDF and ePub files available You can upgrade to the eBook version at www Packt Pub com and as a print book customer you are entitled to a discount on the eBook copy Get in touch with us at service packtpub com for more details At www Packt Pub com you can also read a collection of free technical articles sign up for a range of free newsletters and receive exclusive discounts and offers on Packt books and eBooks PJ PACKT i http PacktLib PacktPub com Do you need instant solutions to your IT questions PacktLib is Packt s online digital book library Here you can access read and search across Packt s entire library of books Why Subscribe e Fully searchable across every book published by Packt Copy and paste print and bookmark content e On demand and accessible via web browser Free Access for Packt account holders If you have an account with Packt at www Packt Pub com you can use this
59. hat we have to copy to our game assets folder Next we have to add some extra dependencies to our C project so that we can interact with the FMOD Designer API These dependencies ship together with the FMOD Ex Programmer s API but we must add the references ourselves as follows 1 Navigate to C C General and add c FMOD fmoddesignerapi api inc to the list of Additional Include Directories entries are separated by semicolons 2 Navigate to Linker General and add C FMOD fmoddesignerapi api lib to the list of Additional Library Directories 3 Navigate to Linker Input and add fmod_event 1lib to the list of Additional Dependencies 4 Navigate to Build Events Post Build Event and add xcopy y C FMOD fmoddesignerapi api fmod_ event dll OutDir to the Command Line list 5 Include the lt fmod_event hpp gt header file from your code Finally the process of loading an FMOD Designer project playing a sound event and modifying some of its parameters is in many ways similar to what we saw in Chapter 2 Audio Playback Let us take a look at the most basic way to do it 69 Intelligent Audio First we must create and initialize an FMOD EventSystem object and load the project file We should also call the update method in every frame and the release method at the end of the game Create an event system object FMOD EventSystem eventSystem FMOD EventSystem Create amp eventSys
60. he initialization process described earlier also assumes that everything will go as planned but a real game should be prepared to deal with any errors Fortunately there is a template provided in the FMOD documentation which shows you how to write a robust initialization sequence It is a bit long to cover here so I urge you to refer to the file named Getting started with FMOD for Windows pdf inside the documentation folder for more information 18 Chapter 2 For clarity all of the code examples will continue to be presented without error checking but you should always check for errors in a real project Project 1 building a simple audio manager In this project we will be creating a SimpleAudioManager class that combines everything that was covered in this chapter Creating a wrapper for an underlying system that only exposes the operations that we need is known as the facade design pattern and is very useful in order to keep things nice and simple Since we have not seen how to manipulate sound yet do not expect this class to be powerful enough to be used in a complex game Its main purpose will be to let you load and play one shot sound effects with very little code which could in fact be enough for very simple games It will also free you from the responsibility of dealing with sound objects directly and having to release them by allowing you to refer to any loaded sound by its filename The following is an example of h
61. he output we need to resample the data so that it matches the sampling rate of the output or the sound will play at a different rate than we expect This operation is not trivial and is beyond the scope of this chapter e If our audio data is in a different format from the output we need to convert the data to the new format first For example we may need to convert a 32 bit floating point sample into a signed 16 bit integer sample This is not that complicated and mostly requires scaling numbers from one range to another e If our audio data has different number of channels from the output we have to adapt the signal to the new number of channels Adapting a mono signal to a stereo is easy as we simply need to send a duplicate of the data to both channels Adapting a stereo signal to mono usually involves adding the values of both channels together and dividing the result by two For the sake of keeping our examples simple we will assume that the audio data has a very specific format so that no conversions need to take place e Ithasasampling rate of 44100 Hz the same as the output e Itis stored in the PCM16 audio format the same as the output e Itonly has one channel mono of data although the output has two channels stereo so that we can see an example of how to implement panning Under these conditions we only need two things to play the sound we need to be able to access the audio data and we need a variable to keep a
62. iii www allitebooks com Preface Audio is certainly one of the most powerful tools at our disposal when it comes to making the players feel something from a video game Audio can serve many different purposes in video games such as giving feedback with sound effects increasing immersion with ambient tracks telling stories with recorded speech or conveying all kinds of emotions through background music Video games have been making use of sound since their earliest days For instance the 1972 classic Pong used a beep sound effect to provide feedback whenever the ball collided with something with different pitches used to distinguish between collisions with the walls collisions with the paddles or the ball leaving the game court Space Invaders on the other hand made a very clever use of its rudimentary background music by progressively increasing the speed of the song as the danger of the alien invasion drew closer thus enhancing the feelings of tension within the player Studies have shown that gamers that played the game without sound did not feel the same sense of urgency and their heart rates did not rise like the ones that played the game with the sound turned on Since those days there have been many advances in technology which allowed audio in games to evolve considerably Most games began using recorded audio instead of crude synthesized tones and new techniques such as 3D audio now allow the players to feel like the s
63. indow events if event type sf Event Closed window close Handle user input if event type sf Event KeyPressed amp amp event key code sf Keyboard Space audio Play explosion wav Place your update and draw logic here 4 Preface audio Update elapsed Place your shutdown logic here return o0 New terms and important words are shown in bold Words that you see on the screen in menus or dialog boxes for example appear in the text like this For all the steps that follow make sure that the Configuration option is set to All Configurations Warnings or important notes appear in a box like this Q Tips and tricks appear like this Reader feedback Feedback from our readers is always welcome Let us know what you think about this book what you liked or may have disliked Reader feedback is important for us to develop titles that you really get the most out of To send us general feedback simply send an e mail to feedback packtpub com and mention the book title via the subject of your message If there is a topic that you have expertise in and you are interested in either writing or contributing to a book see our author guide on www packtpub com authors Customer support Now that you are the proud owner of a Packt book we have a number of things to help you to get the most from your purchase Downloading the example code You can download the
64. ing speed dynamically We start by creating a simple event with the footstep audio files following the advices given earlier in order to avoid repetition and set the playback mode to granular Then we adjust the grain interval so that the time between each footstep corresponds to the speed of the character walking and increase the polyphony so that each footstep can sound without having to wait for the previous to end We can also set slightly different maximum and minimum grain interval values to reinforce the variations of the sound even further 60 Chapter 5 Creating a breaking glass sound effect Another approach we can use to reduce repetition in our sound effects is to generate them at runtime as a combination of a few smaller sound fragments For example to simulate the sound of a glass object falling to the ground and shattering we could have a pool of different glass breaking sounds and always play two or three of them in quick succession Combined with the usual volume and pitch variations the result is a sound effect that will sound different most of the time To implement this type of sound effect we need to use the granular playback mode and set both the polyphony and the grain count parameters to the number of sound fragments that we want to use at once For the breaking glass sound effect we could set the polyphony and grain count to 2 or 3 and set a very small grain interval for example 200 ms so that the sou
65. io file as a sound and working at a higher level of abstraction with sound events or sound cues in some engines The following figure demonstrates how we have been approaching audio in our games so far Game Audio files Load audio files Play audio files Control sound playback a and parameters directly Write code to handle custom sound behavior Programmer In this model we can see that the game interacts directly with the audio files and that the code is responsible for using these audio files in a way that is appropriate for the game which usually requires the creation of specialized codes When we move over to using a high level audio engine such as the FMOD Designer the process is significantly different as we can see in the following figure 54 Chapter 5 Audio profile file Game Load audio project files Sound Event Trigger sound events Custom parameters Update parameters Custom behavior written specifically for the game r Sound Designer 1 T Programmer The first difference in this model is that the game does not interact directly with audio files Instead it interacts with entities known as sound events which may contain multiple audio files and encapsulate all of the custom behavior and parameters of the sound that were previously inside the game This separation makes the game code a lot simpler and provides a better environment for a sound designer to work Notice also that there is an
66. ion In this approach the audio system modifies the mix of the song in real time depending on events occurring in the game This can consist for example of adding new instruments to the song or making the music play faster or slower to match the gameplay The easiest way to implement this type of interactive music in the FMOD Designer is by using multi track events in combination with specially prepared multi channel audio files which we can create using audio editing software such as Audacity This usually requires splitting up the music into layers and adding each of the layers to a different audio channel in the file Then using the Channel Mix effect on a multi track event we can easily control the individual volumes of each audio channel based on the value of a parameter The most common application of this technique is to create a tension or excitement parameter so that the song gets more intense by adding more layers as the value increases The famous Japanese composer Koji Kondo is very fond of creating interactive music using this approach Some recent examples include e On the Super Mario Galaxy levels where Mario rides on top of a star ball the speed at which Mario moves completely determines the pitch playback rate and even the amount of instruments playing in the song e On the market area of The Legend of Zelda Skyward Sword each merchant has its own variation of the market theme As the link approaches one of
67. it can be implemented by adding all the audio signals together and clamping the result to the available range Looking at our WriteSoundData method all we need to do is change the lines of code that write to the data array so that the samples are added to the existing values instead of completely replacing them void MyChannel WriteSoundData PCM16 data int count if sound paused return fOr inte a Oe i lt count i 42 2 4 if position gt sound scount if Loop 4 position 0 else Stop return float value sound sdatal int position volume data i PCM16 value leftGain datal il data i 1 PCM16 value rightGain data i 1 position pitch 89 Low level Audio In our main application instead of having a single channel instance we can now create multiple instances and call WriteSoundData on all of them std vector lt MyChannel gt channels FMOD RESULT F CALLBACK WriteSoundData FMOD SOUND sound void data unsigned int length Clear output memset data 0 length Get data in the correct format and calculate sample count PCM16 pcmData PCM16 data int pemDataCount length 2 Tell every channel to write to the output for int i 0 i lt channels size i channels i WriteSoundData pcmData pcmDataCount return FMOD OK Implementing a delay effect We have already discussed back in Chapter 4 3D Audio that
68. l data is continuous and numbers on a computer are discrete samples need to be rounded to the nearest available number in a process known as quantization Samples are usually stored as integer numbers but it is also possible to use floating point numbers as shown in the following example P 22235 058 045 058 070 osi om oss os 100 PCM Data 9 www allitebooks com Audio Concepts There are two ways to control the quality of the sampled audio e Sampling rate Also known as the sampling frequency it is the amount of samples taken for each second of audio According to the Nyquist sampling theorem the sampling rate should be at least twice as high as the highest frequency of the analog signal in order to allow a proper reconstruction You will usually work with values of 44 100 Hz or 48 000 Hz The following figure compares sampling at different rates Amplitude Amplitude Higher Sampling Rate Lower Sampling Rate e Bit depth Also known as the resolution it is the amount of bits used to represent a single sample This controls the number of possible discrete values that each sample can take and needs to be high enough to avoid quantization errors You will usually work with bit depths of 16 bits or 24 bits stored as integer numbers or 32 bits stored as floating point numbers The following figure compares sampling at different resolutions Amplitude Amplitude pe Eee een A A A A iS Higher Bit Depth Lower Bit D
69. le these days such as DirectSound Core Audio PortAudio OpenAL FMOD or Wwise Some are available only on certain platforms while others work almost everywhere Some are very low level providing little more than a bridge between the user and the sound card driver while others provide high level features such as 3D sound or interactive music For this book we will be using FMOD a cross platform audio middleware developed by Firelight Technologies that is extremely powerful yet easy to use However you should try to focus more on the concepts covered instead of the API because understanding them will allow you to adapt to other libraries more easily since a lot of this knowledge is interchangeable For starters we will learn how to install FMOD how to initialize and update the audio system and how to get it to play an audio file At the end of the chapter we will work through the creation of a very simple audio manager class which encapsulates all of these tasks behind a minimalistic interface Understanding FMOD One of the main reasons why I chose FMOD for this book is that it contains two separate APIs the FMOD Ex Programmer s API for low level audio playback and FMOD Designer for high level data driven audio This will allow us to cover game audio programming at different levels of abstraction without having to use entirely different technologies Audio Playback Downloading the example code A You can download the e
70. lease contact us at copyright packtpub com with a link to the suspected pirated material We appreciate your help in protecting our authors and our ability to bring you valuable content Questions You can contact us at questions packtpub com if you are having a problem with any aspect of the book and we will do our best to address it 6 Audio Concepts Programming the audio component of a game is a lot easier these days thanks to all the powerful audio libraries that are available These libraries ease the burden on the developers by taking care of most of the low level implementation details While this is a good thing it also makes it easier to dismiss the need to understand sound theory For instance we can easily play a sound file without knowing anything about its representation in memory However even when we are using an audio library there are still situations that will require some theoretical knowledge For instance we will often find parameters and function names related to the theory such as the frequency of a sound or the bit depth of an audio buffer Knowing the meaning of these concepts is important to ensure that we are using them properly The goal of this chapter is to serve as a light introduction to the concepts that we will need the most during the course of this book Sound waves Sound is created from the vibrations of objects These vibrations produce variations in the atmospheric pressure which
71. llowing figure shows the contents of a WAV file in a canonical format Note that if the file contains compressed data the format subchunk can contain more data than the one shown in the following figure It is also possible for other chunks to appear in the file or in a different order Content Type Size Offset RIFF char 4 4 u 32 WAVE char 4 fmt charldl 16 u32 1forPCM u16 eg 1or2 u16 e g 44100 u32 u 32 u 16 eg 16 u16 Data Chunk ID data char 4 Data Chunk Size n u 32 n samples byte n Now that we have a table listing the contents of a canonical WAV file let us create a class to load and store all of the information that we care about from the file that is the sampling rate bit depth number of channels and the audio data Keeping in line with what we used previously in FMOD we will name this class MySound For simplicity every member of the class has public accessibility although we could provide a few accessor methods instead while making the data private class MySound public MySound const char path MySound U32 samplingRate U16 numChannels U16 bitsPerSample PCM16 data U32 count 78 Chapter 6 On the constructor we open the audio file and read all of the relevant data into the member variables Note that there is no error checking anywhere and that this will only work under the conditions described earlier H Hinclude lt iostream gt Hinclude
72. lly a variable with a certain range of permitted values that the game code can modify The way the FMOD Designer represents parameters might look like a timeline but it is important to understand that a parameter is a generic value and does not necessarily represent time The first parameter we create is marked as the primary parameter and it determines which sounds to play In the following example only the two sounds that are in contact with the red line representing the current value of the primary parameter will be playing Changing the value of the parameter to any value above 0 5 would replace the Frogs sound with the Crickets sound We can create multiple parameters in the same event although only one of them will be marked as primary 0 000 0 200 0 400 0 600 0 800 on E Submarine Environment Clock Another use of parameters is to control the sound properties of each layer In order to do that we must first add an effect to the layer we want to control by right clicking on the layer and selecting the Add effect option Effects can vary from a simple volume or pitch control to more complex DSP effects such as a distortion or a delay Volume Pitch Pan Surround pan 3D Pan Level 30 Speaker spread Speaker Level Channel Mix Having an effect added to a layer and a parameter selected we can draw curves on the layer which represent how the properties of the effect should vary with the values of the parameter
73. lt fstream gt MySound MySound const char path Open file stream for input as binary std ifstream file path std i0s in Sstd slos sbinary Read number of channels and sample rate file seekg 22 file read char amp numChannels 2 file read char amp samplingRate 4 Read bits per sample file seekg 34 file read char amp bitsPerSample 2 Read size of data in bytes U32 length file seekg 40 file read char amp length 4 Allocate array to hold all the data as PCM samples count Length 7 23 data new PCM16 count Read PCM data file read char data length The destructor takes care of cleaning up the memory allocated in the constructor to hold the audio data MySound MySound delete data 79 Low level Audio Playing a sound Now that we have all of the audio data stored in memory we are ready to begin playing the sound In order to do so we must essentially take each of the values stored in the data array and send them in order to the audio card in our case using the callback method that we created earlier If the format sampling rate and number of channels in the audio data are the same as the output then this process is as simple as copying values from one array to another However the process becomes significantly more complicated if they differ in any way in particular e If our audio data has a different sampling rate from t
74. mize Every Spawn 480 530 Oea Eee Pitch Randomization 2 Ej media 201 1 Footsteps_concrete_06 0gg 12 50 Spawn Time 480 530 Maximum Polyphony ft Trigger Delay en ooo i mediai201i Footsteps_concrete_OF ogg 12 50 Play Count Maximum Polyphon i mediai201 1 footsteps_concrete_08 0gg 12 50 ee z fs a Trigger Delay 0 0 3D Min Position Randomization 3D Max Position Randomization Notes Source copyright Stephan Schrtze w 62 Chapter 5 To create a multi track event follow the same steps used to create a simple event but select the Add Multi Track Event option instead Events Sound Des Music Banks Groups Categories 4dd Simple Event Add Mulki Track Event Pot lt De a A multi track event is divided into layers or tracks with each layer being able to contain multiple sound defs Adding a new layer or adding sound to a layer are both handled by right clicking on the following interface and selecting the Add layer or Add sound option from the context menu forickets Submarine Environment Clack By default the preceding example will play all three sound defs at the same time This behavior changes as soon as we add a parameter to the sound which can be done by right clicking on the dark area on top of the sounds region and selecting the Add parameter option from the list Add parameter A l Cam mn ABA ee S T 63 Intelligent Audio A parameter is essentia
75. mples of how to use them in the context of a game Coverage of the topic of interactive music will have to be more superficial because its breadth exceeds the scope of this book Simple events Simple events are the easiest to use as well as the least resource intensive We should therefore try to use simple events whenever they are enough for our requirements With a simple event we can e Create a sound composed by multiple audio files e Play audio files sequentially or in a random order e Randomize sound properties such as volume or pitch e Control the looping behavior of the sound e Play multiple audio files at once or at certain intervals To create a simple event go to the Events section right click on top of any Event Group and then select the Add Simple Event option If there is no Event Group created we can create one from the same context menu Event groups behave like folders and serve to organize all of our events Events Sound Defs Music Banks Groups Categories ehi Templates fa fsi Forest S Add Simple Event Add Multitrack Event Adda Framt ream 57 Intelligent Audio With the event selected the next step is to add the audio files that compose it to the Playlist pane either through the right click context menu or by dragging some audio files into it If we intend to play the audio files in a random order we can specify the probability of each file playing through the right click conte
76. n properties of sound that were described in Chapter 1 Audio Concepts such as volume and pitch We will also see how FMOD lets us group sounds into categories in order to control multiple sounds at once At the end of the chapter we will expand the audio manager from the previous chapter and make it more flexible and appropriate for use in games This extended audio manager will provide a distinction between songs and sound effects and handle each of them differently We will see how to implement a fade in fade out effect using simple volume manipulation and how to add a variation to sound effects with a bit of randomness The audio manager will also expose individual volume control for each category making it easy to control from a game s option screen The channel handle Let us start with a quick reminder from last chapter When we use the playSound method and pass the address of an FMOD Channel pointer to the fourth parameter we get a channel handle in return FMOD Channel channel system gt playSound FMOD CHANNEL FREE sound false amp channel Through this handle we can control the sound in many ways This handle remains valid while the sound has not finished playing or until we explicitly stop the sound If we try to perform an operation on the channel after the sound has stopped nothing happens Instead the method we called returns an error stating that the channel handle is invalid or already in use by another s
77. n the value of a parameter e Modify any of the sound or effect properties from a parameter 61 Intelligent Audio Before creating a multi track event we must prepare a sound def for each of the sounds that we intend to use The process is similar to creating a simple event although the interface is a bit different Head over to the Sound Defs section right click on top of any folder and select one of the Add sound def options Sound Defs Music Banks Add sound def fi NoteManip sans Add sound defis Fram sound files ie ArmbientLoo Sod sound def Folder 4 J Engine SS ee ee ee ee ee eee The interface used to create a sound def is a bit like a condensed version of the simple event interface with the playlist on the left and every other property on the right Since most of the properties control something that we have already seen in simple events there is no need to repeat that information here I Sounds isi Footsteps Concrete gt ty Display randomization in Percentage Weighting gt ty a a i noe A Wd Ji i mediai201 1 footsteps_concrete_01 0gg 12 50 Footsteps Concrete Play Mode Random Mo Repeat volume fy media 201 1 footsteps _concrete_O3 0gg 12 50 volume Randomization i media 201 1 Footsteps_concrete_O4 0gg 12 50 Pitch Pitch Randomization iT mediai201 1iFootsteps concrete_OF 0gg 12 50 m mediai201 1 footsteps_concrete_05 0gg 12 50 Pitch Randomization Behavior Rando
78. nce the position value So far we have used a position variable that was an integer and incremented its value by a full unit every time In order to provide pitch control we will change that variable to a floating point number and add a pitch variable that determines how much to increment the position By default the pitch variable will have a value of 1 which plays the sound at the normal pitch A value of 2 will double the frequency of the sound making it sound one octave higher and a value of 0 5 will halve the frequency of the sound making it sound one octave lower For practical reasons we will limit its value to the range between 0 25 two octaves below the original sound and 4 two octaves above the original sound public float GetPitch const return pitch void SetPitch float value if value lt 0 25f pitch 0 25 5 else if value gt 4 0f pitch 4 0f else pitch value private float position float pitch Inside our WriteSoundData method we increment the position variable by the pitch amount The hardest part in the process is how to convert the position variable that is now a floating point number back into an array index The simplest solution is to use a simple cast which truncates the value to an integer and that is what we will use void MyChannel WriteSoundData PCM16 data int count if sound paused return for int i 0 1i lt count i 2 f if position gt sound
79. nd simultaneously On a sound with multiple channels we can modify the volume of each channel separately using the set Input ChannelMix method This works for any amount of channels by taking an array of volume levels as the first parameter and the number of channels as the second The following is an example for a stereo sound that mutes the left channel float levels 2 0 0f 1 0f channel gt setInputChannelMix levels 2 Controlling the pitch Controlling the pitch is not as straightforward as controlling the volume We already know that modifying the frequency of a sound changes its pitch and the channel handle actually has a set Frequency method just for that channel gt setFrequency 261 626E 27 Audio Control However it does not work the way some of us might expect For example the middle C note on a piano has a frequency of approximately 261 626 Hz so we might expect that setting the frequency to that value would make the sound assume a pitch close to the middle C note but this is not the case In order to understand this problem let us first turn our attention to the get Frequency method If we call this method on a channel with its original frequency what we get in return is actually the sampling rate of the sound This means that any frequency values that we set must be relative to this value or in other words that any values above the original sampling rate of the sound will increase its pi
80. nd effects are the easier of the two categories to play The PlaySFx method takes the path of the sound and a pair of minimum and maximum volume and pitch values Then it searches for the sound in the correct map and plays it back like before except that it sets the volume and pitch of the sound using random values generated within the selected ranges void AudioManager PlaySFX const std string amp path float minVolume float maxVolume float minPitch float maxPitch Try to find sound effect and return if not found SoundMap iterator sound sounds CATEGORY SFX find path if sound sounds CATEGORY SFX end return Calculate random volume and pitch in selected range float volume RandomBetween minVolume maxVolume float pitch RandomBetween minPitch maxPitch Play the sound effect with these initial values FMOD Channel channel system gt playSound FMOD CHANNEL FREE sound gt second true amp channel channel gt setChannelGroup groups CATEGORY SFX channel gt ssetVolume volume float frequency channel gt getFrequency amp frequency channel gt setFregquency ChangeSemitone frequency pitch channel gt ssetPaused false The preceding code makes use of two helper methods ChangeSemitone which was already shown earlier in this chapter and RandomBetween which can be seen in the following code snippet include lt stdlib h gt Hinclude lt time h g
81. nds end return Otherwise play the sound system gt playSound FMOD CHANNEL FREE sound gt second false 0 We could have tried to automatically load the sound in the case when it was not found In general this is not a good idea because loading a sound is a costly operation and we do not want that happening during a critical gameplay section where it could slow the game down Instead we should stick to having separate load and play operations A note about the code samples Although this is a book about audio all the samples need an environment to run on In order to keep the audio portion of the samples as clear as possible we will also be using the Simple and Fast Multimedia Library 2 0 SFML http www sfml dev org This library can very easily take care of all the miscellaneous tasks such as window creation timing graphics and user input which you will find in any game For example here is a complete sample using SFML and the SimpleAudioManager class It creates a new window loads a sound runs a game loop at 60 frames per second and plays the sound whenever the user presses the space key include lt SFML Window hpp gt include SimpleAudioManager h int main sf Window window sf VideoMode 320 240 AudioPlayback sf Clock clock Place your initialization logic here SimpleAudioManager audio audio Load explosion wav Start the game loop while window isOpen Onl
82. nds play almost at the same time Creating an ambient track of singing birds The same technique used to generate the sound of a glass breaking can also generate long looping and ever changing ambient tracks A common example is to take a few small audio files of birds singing and by triggering them randomly at different times and with different volume and pitch we can easily give the impression of being in a forest where there are several different birds singing The process is very similar to the previous effect except that this time we should set a large polyphony such as 15 a grain interval value of around 1s and an infinite grain count so that the sound does not stop playing Modifying the 3D position randomization properties can also be useful to create a volumetric sound and give the impression that every bird is located in a different point in space instead of every sound coming from the same spot Multi track events Multi track events are significantly more powerful than simple events In fact before adding any sound to a multi track event we must turn it into a sound def which has almost the same functionality as a simple event With a multi track event we can e Perform everything that we could with a simple event e Create multiple layers of sounds that play at the same time e Apply one or more DSP effects to each layer e Create custom parameters to modify the sound in real time e Play different sounds depending o
83. non trivial task This is particularly true with compressed audio file formats which require decoding the audio data using some algorithm before we can use it in our application In general it is usually better to use an audio engine or an external library to read the contents of an audio file For educational purposes we will be reading the audio data from a WAV file We will however work under the assumption that the WAV file we read from is in the canonical form that is it contains only a format and a data subchunk in that order and that the audio data is stored without any compression Under these conditions we know where all of the data is stored and can simply index into the file to read it That is certainly not the case for every WAV file which would require a more complex loading sequence The WAV file format builds upon the more generic RIFF file format A RIFF file is divided into chunks of data Every chunk begins with a 4 character ASCII identifier and a 32 bit integer describing how much data is stored in the chunk Next there is the actual data of the chunk which varies depending on the type of the chunk All WAV files contain at least the following three chunks with two of them considered subchunks of the first A RIFF chunk containing the string literal WAVE e A Format subchunk containing information about the audio file e A Data subchunk containing the actual audio data 77 Low level Audio The fo
84. on and the fifth parameter is the polygon data itself The sixth parameter returns an index which can be used to perform further operations on the polygon FMOD VECTOR vertices 3 Fill with triangle vertices int polygonIndex Gets an index for the new polygon geometry gt addPolygon 0 5f 0 5f false 3 vertices amp polygonIndex We should create the polygon using vertices in object space not in world space Then in order to position the geometry the world we can use a combination of the setPosition setRotation and setScale methods 49 www allitebooks com 3D Audio Effects Besides all of the 3D audio simulations described earlier there is another subject that we should cover DSP effects A DSP effect which stands for digital signal processing is an algorithm that takes sound data as input modifies it in some way and returns a new set of data as output Most effects either manipulate the amplitudes or frequencies of the sound data or add multiple sounds together frequently that sound is a delayed and attenuated version of itself The following is a list of some common types of DSP effects Normalize This effect scales the volume of the sound so that the peak amplitude is at the maximum volume level Compressor This effect makes the loud sections of the sound quieter then brings the entire volume up to compensate reducing the dynamic range of the sound Distortion This effect distorts the sound makin
85. oncepts of digital audio theory In particular we saw that a simple array of numbers could represent an audio signal and talked about topics such as PCM sampling rate bit depth and multi channel audio In this chapter we will be putting all of those concepts into practice so make sure you understand them before continuing For starters let us look into the meaning of audio data both in theory and in code Low level Audio Audio data is nothing more than a sequence of numbers that represent the amplitude of a sound wave at even time intervals However there are many ways to represent numbers on a computer depending on the amount of memory used to represent them whether they should be able to store negative numbers and whether the numbers are integers or floating point numbers These differences result in the multiple data types provided by C to store numbers such as int short float and double It makes sense then that audio data can also be stored in several formats depending on the chosen data type In this chapter we will limit ourselves to the most common audio format which is the signed 16 bit linear PCM format In this format every sample is a 16 bit signed integer a signed short in C ranging from 32768 at the minimum amplitude to 32767 at the maximum amplitude To simplify the notation when dealing with PCM samples and other quantities we will be using the following aliases typedef signed short PCM16 typedef
86. ook you will find a number of styles of text that distinguish between different kinds of information Here are some examples of these styles and an explanation of their meaning Code words in text database table names folder names filenames file extensions pathnames dummy URLs user input and Twitter handles are shown as follows Notice that the function returns the system object through a parameter 3 Preface A block of code is set as follows Hinclude lt math h gt float ChangeOctave float frequency float variation Static Tloat Octave ratio 2 01 return frequency pow octave ratio variation float ChangeSemitone float frequency float variation static float semitone ratio pow 2 0f 1 0f 12 0f return frequency pow semitone ratio variation When we wish to draw your attention to a particular part of a code block the relevant lines or items are set in bold include lt SFML Window hpp gt include SimpleAudioManager h int main sf Window window sf VideoMode 320 240 AudioPlayback sf Clock clock Place your initialization logic here SimpleAudioManager audio audio Load explosion wav Start the game loop while window isOpen Only run approx 60 times per second float elapsed clock getElapsedTime asSeconds if elapsed lt 1 0f 60 0f continue clock restart sf Event event while window pollEvent event Handle w
87. or pair to manage the sound system The private class members on the other hand can tell us a lot about the inner workings of the class At the core of the class is an instance of FMOD System responsible for driving the entire sound engine The class initializes the sound system on the constructor and releases it on the destructor Sounds are stored inside an associative container which allows us to search for a sound given its file path For this purpose we will be relying on one of the C Standard Template Library STL associative containers the std map class as well as the std string class for storing the keys Looking up a string key is a bit inefficient compared to an integer for example but it should be fast enough for our needs An advantage of having all the sounds stored on a single container is that we can easily iterate over them and release them from the class destructor Since the code for loading and streaming audio file is almost the same the common functionality has been extracted into a private method called LoadOrStream to which Load and Stream delegate all of the work This prevents us from repeating the code needlessly 20 Chapter 2 Initialization and destruction Now let us walk through the implementation of each of these methods First we have the class constructor which is extremely simple as the only thing that it needs to do is initialize the system object SimpleAudioManage
88. ound if that is the case Audio Control Something that might be confusing is that this FMOD channel is not the same type we talked back in Chapter 1 Audio Concepts when we discussed multi channel audio This is simply the name FMOD gives to each of the slots it uses to play sounds simultaneously Controlling the playback We already know how to play audio files but it is also important to know how to stop them from playing This is particularly important for looping sounds because otherwise they would keep repeating forever Usually all we have to do is call the stop method on the channel handle channel gt stop When a sound stops playing because it reached the end and it is not set to loop or because we stopped it ourselves its channel becomes free for other sounds to use This means that once we stop a sound there is no way to resume it If we need to stop a sound temporarily and resume it at a later time we need to use the setPaused method Pause the sound channel gt setPaused true Resume the sound channel gt setPaused false Most methods that start with set are accompanied by an equivalent get method such as get Paused that we can use to check the current value of that property The following is a function that uses both methods in conjunction with each other to toggle the paused state of a channel void TogglePaused FMOD Channel channel bool paused channel gt getPaused amp
89. ound is coming from all around them and interacting with the game environment Music has also played a very important role in video games The popular Final Fantasy games owe a great portion of their emotional impact to the sweeping cinematic soundtracks composed by Nobuo Uematsu The most memorable scenes in the series would have not been the same without the music that accompanied them Preface Many developers and composers have also looked into ways of making the music react to the game play For example starting with Monkey Island 2 LeChuck s Revenge every graphic adventure game that LucasArts created uses a custom interactive music system called iMUSE which among other features allows seamless musical transitions between themes as the player moves from one room to another There are even games that incorporate audio concepts directly into their main gameplay mechanics such as the songs that the player has to memorize and play in The Legend of Zelda Ocarina of Time and games that revolve entirely around sound with the most popular examples being rhythm games such as PaRappa the Rapper Dance Dance Revolution or Guitar Hero However despite being such an important part of video games many game development books skim through the subject of audio programming Even the ones that dedicate a chapter to audio often only teach you the very basics such as loading and playing audio files or use outdated audio engines instead of the one
90. oup or the system object itself using the addDSP method of the corresponding object You can also add more than one DSP effect to the same object which chains them together automatically channel gt addDSP dsp 0 The second parameter allows more control over the DSP connection but we will ignore it for our simple examples Finally most DSP effects have a set of parameters that you can control using the setParameter method once again check the documentation for a list of all the available parameters dsp gt setParameter FMOD DSP ECHO DECAYRATIO 0 75f Example 1 time stretching As our first application of DSP effects here is an example that shows how to change the playback speed of a sound without affecting its pitch To do this we need to combine a regular frequency change which modifies both the pitch and the speed of the sound with a pitch shift DSP effect in order to return the pitch back to normal Play at half speed float amount 0 5 Modify frequency which changes both speed and pitch float frequency channel gt getFregquency amp frequency channel gt setFreguency frequency amount Create a pitch shift DSP to get pitch back to normal by applying the inverse amount FMOD DSP dsp system gt createDSPByType FMOD DSP TYPE PITCHSHIFT amp dsp dsp gt setParameter FMOD DSP PITCHSHIFT PITCH 1 0f amount 51 3D Audio dsp gt setParameter FMOD DSP PITCHSHIFT F
91. ow to create adaptive and interactive sound events and music 2 Preface Chapter 6 Low level Audio provides basic information on how to work with audio at a very low level by manipulating and writing audio data directly What you need for this book For this book you will need the following software C IDE Instructions are provided for Microsoft Visual Studio but you should be able to use any C IDE or compiler The Express version of Visual Studio is free and can be downloaded from the Microsoft website e FMOD Ex Needed for chapters 2 4 and 6 and can be downloaded for free from www fmod org e FMOD Designer Needed for chapter 5 Can be downloaded for free from www fmod org e SFML All of the code samples on the website also use SFML Version 2 0 to handle other tasks such as window management graphics and input handling Free download from www sfml dev org Who this book is for This book is oriented towards C game developers who have little or no experience with audio programming and would like a quick introduction to the most important topics required to integrate audio into a game You will need an intermediate knowledge of C to be able to follow the code examples in the book including an understanding of basic C Standard Library features such as strings containers iterators and streams Some game programming experience is also recommended but not mandatory Conventions In this b
92. ow to use the class SimpleAudioManager audio audio Load explosion wav audio Play explosion wav From an educational point of view what is perhaps even more important is that you use this exercise as a way to get some ideas on how to adapt the technology to your needs It will also form the basis of the next chapters in the book where we will build systems that are more complex Class definition Let us start by examining the class definition include lt string gt include lt map gt include lt fmod hpp gt typedef std map lt std string FMOD Sound gt SoundMap class SimpleAudioManager public SimpleAudioManager SimpleAudioManager 19 www allitebooks com Audio Playback void Update float elapsed void Load const std string amp path void Stream const std string amp path void Play const std string amp path private void LoadOrStream const std string amp path bool stream FMOD System system SoundMap sounds i From browsing through the list of public class members it should be easy to deduce what it is capable of doing The class can load audio files given a path using the Load method The class can stream audio files given a path using the Stream method The class can play audio files given a path using the Play method granted that they have been previously loaded or streamed There is also an Update method and a constructor destruct
93. p hierarchy automatically without overwriting the values stored inside the channels The way these values are applied depends on the type of operation For operations such as pausing and muting the values in the channel group override the values in the children This means that if the channel group is paused every channel will remain paused regardless of their real values On the other hand if the channel group is not paused the individual values in the channels are considered For volume and pitch the values in the channel group are multiplied by the values in the children For example a channel at 80 percent volume inside a channel group at 50 percent volume will play at 40 percent volume instead 31 Audio Control Project 2 improving the audio manager In this project we will build on top of the simple audio manager developed in the last chapter and make it more flexible and game oriented This time besides loading and playing sounds we will also be able to stop them and control their volume which is necessary in almost every game Furthermore we will divide all sounds into two categories each with its own set of features and behaviors Sound effects SFXs Sounds that are loaded into memory and do not loop Multiple instances can be played at the same time Their volume and pitch can be controlled directly or randomized within a user defined range to add variation to the sound Songs Sounds that are streame
94. paused channel gt setPaused paused Another common operation is to seek the sound to a different position in the file This is done with the setPosition method which takes a number representing the position we want to seek to and the units we are specifying that position in milliseconds in the following example This is useful if we want to make a sound start from the beginning after unpausing it channel gt setPosition 0 FMOD TIMEUNIT MS 26 Chapter 3 Finally if we have a looping sound we can use the setLoopCount method to control the number of times the sound should loop The following example shows some of the possible parameters with the default being 1 to loop endlessly Repeat endlessly channel gt setLoopCount 1 Play once then stop channel gt setLoopCount 0 Play three times then stop channel gt setLoopCount 2 Controlling the volume Next we will see how to control some of the main properties of sound starting with its volume This is done with a simple call to the setVolume method which takes a value ranging from 0 silence to 1 maximum volume Channel gt setVolume 1 0 Similar to the way we paused the sound earlier we can also silence it temporarily by using the setMute method Once we unmute the sound it continues playing at its previous volume channel gt setMute true Both the methods preciously mentioned modify all channels of the sou
95. que results in a smoother transition from one side to the other than using regular linear interpolation with 50 percent in the middle because of the way we perceive sound intensity 29 www allitebooks com Audio Control Stereo sounds on the other hand use a simpler formula referred to as setting the balance of the sound Using this approach both outputs are already at 100 percent in the center position and panning to one side only decreases the volume of the opposite channel in a linear fashion The following figure demonstrates both the approaches Constant Power Balance Panning Panning 0 i 0 Grouping channels together Another great feature of FMOD is that it lets us add different channels to a group and control them simultaneously This is very useful for video games where sound tends to fall into categories such as background music sound effects or speech To create a channel group we use the createChannelGroup method of the system object FMOD ChannelGroup musicGroup system gt createChannelGroup music amp musicGroup Then we can easily add a channel to a group using the setChannelGroup method of the channel object channel gt setChannelGroup musicGroup It is also possible to add a group as a child of another group creating a hierarchy This is done using the addGroup method of the parent channel group object channelGroup gt addGroup anotherGroup There is also a glob
96. r SimpleAudioManager FMOD System Create amp system system gt init 100 FMOD INIT NORMAL 0 Updating is even simpler consisting of a single method call void SimpleAudioManager Update float elapsed system gt update The destructor on the other hand needs to take care of releasing the system object as well as all the sound objects that were created This process is not that complicated though First we iterate over the map of sounds releasing each one in turn and clearing the map at the end The syntax might seem a bit strange if you have never used an STL iterator before but all that it means is to start at the beginning of the container and keep advancing until we reach its end Then we finish off by releasing the system object as usual SimpleAudioManager SimpleAudioManager Release every sound object and clear the map SoundMap iterator iter for iter sounds begin iter sounds end iter iter gt second gt release sounds clear Release the system object system gt release system 0 21 Audio Playback Loading or streaming sounds Next in line are the Load and Stream methods but let us examine the private LoadOrStream method first This method takes the path of the audio file as a parameter and checks if it has already been loaded by querying the sound map If the sound has already been loaded there is no need to do it again so the method
97. r it is also worth realizing that not every sound needs to come from an audio file It is also possible to generate sounds from scratch using only mathematical formulas We call this process sound synthesis and there are entire books just about this subject Certain sound waves are particularly common in sound synthesis because of how easy they are to calculate We have already talked about one of these sound waves before the sine wave Other common examples are the square wave the sawtooth wave and the triangle wave all represented in the following figure AHEHE Sine Wave Square Wave BAPA Sawtooth Wave Triangle Wave 92 Chapter 6 We will now see how to synthesize each of these sound waves by creating a class MyOscillator The use case for this class is pretty much the same as the MyDelay class described earlier just create an instance of it and call the WriteSoundData method from the audio callback to make it play include lt math h gt Hdefine PI 3 14159265359 define TWO PI 6 28316530718 class MyOscillator public MyOscillator void SetVolume double value volume value void SetFrequency double frequency void WriteSoundData PCM16 data int count private double phase double increment double volume Pe The class contains three member variables phase which describes how far we are along the sound wave increment which depends on the frequency of the sound and describes ho
98. r the sound of a gun If we use the exact same audio file every time the player will usually notice the repetition after some time which is undesirable in most cases Using simple events we can easily make these sound effects more interesting and dynamic just by providing a few variations of the sound and letting the audio engine pick one randomly Adding a very small volume and pitch variation to the sound can also do wonders as long as the variation is not large enough to change the overall nature of the sound Values along the lines of 3 dB for the volume and 2 semitones for the pitch are usually good starting points Creating a footsteps sound loop There are several ways we can use a footsteps sound effect in a game For example we could have an audio file containing the sound of a single footstep and trigger it once for every step the character takes inside the game world or we could have a looping audio file with a walking sound and play it constantly whenever the character is walking The first approach requires more work inside the game while the second approach takes more memory as the audio file needs to be longer Using a simple event we can combine both approaches by taking an audio file of a single footstep and setting up the event so that it performs the looping using time intervals that are appropriate for a certain walking speed Later when working with multi track events we will also see a way to vary the walk
99. re is only one decode buffer per stream Therefore for sound effects that have to be played multiple times simultaneously you have to either load them into memory or open multiple concurrent streams As a rule of thumb streaming is great for music tracks voice cues and ambient tracks while most sound effects should be loaded into memory The second and third parameters allow us to customize the behavior of the sound There are many different options available but the following list summarizes the ones we will be using the most Using FMOD_DEFAULT is equivalent to combining the first option of each of these categories e FMOD LOOP OFF and FMOD LOOP NORMAL These modes control whether the sound should only play once or loop once it reaches the end e FMOD HARDWARE and FMOD _ SOFTWARE These modes control whether the sound should be mixed in hardware better performance or software more features 16 Chapter 2 e FMOD 2D and FMOD_ 3D These modes control whether to use 3D sound We can combine multiple modes using the bitwise OR operator for instance FMOD _ DEFAULT FMOD_LOOP_NORMAL FMOD_SOFTWARE We can also tell the system to stream a sound even when we are using the createSound method by setting the FMOD_CREATESTREAM flag In fact the createStream method is simply a shortcut for this When we do not need a sound anymore or at the end of the game we should dispose of it by calling the release method of the sound o
100. returns Otherwise the file is loaded or streamed depending on the value of the second parameter and stored in the sound map under the appropriate key void SimpleAudioManager LoadOrStream const std string amp path bool stream Ignore call if sound is already loaded if sounds find path sounds end return Load or stream file into a sound object FMOD Sound sound if stream system gt createStream path c str FMOD DEFAULT 0 amp sound else system gt createSound path c str FMOD DEFAULT 0 amp sound Store the sound object in the map using the path as key sounds insert std make pair path sound With the previous method in place both the Load and the Stream methods can be trivially implemented as follows void SimpleAudioManager Load const std string amp path LoadOrStream path false void SimpleAudioManager Stream const std string amp path LoadOrStream path true Playing sounds Finally there is the Play method which works the other way around It starts by checking if the sound has already been loaded and does nothing if the sound is not found on the map Otherwise the sound is played using the default parameters void SimpleAudioManager Play const std string amp path Search for a matching sound in the map SoundMap iterator sound sounds find path 22 Chapter 2 Ignore call if no sound was found if sound sou
101. rojection cone using the set3DConeOrientation and set 3DConeSettings methods FMOD VECTOR direction 1 0f 2 0f 3 0 channel gt sset3DConeOrientation amp direction channel gt set3DConeSettings 30 0 60 0f 0 5f The set3DConeOrientation method takes a vector defining the main direction of the sound cone The set 3DConeSettings method takes three parameters containing the inner angle the outer angle and the outer volume of the sound cone The sound source is at full volume when the listener is within the inner angle and attenuates towards the outer volume as the listener moves outside that angle Setting the audio source s range We can control the overall distance where a sound is still audible with the set 3DMinMaxDistance method channel gt sset3DMinMaxDistance 1 0 10000 0 We specify the range of the sound as a pair of values the minimum distance and maximum distance The minimum distance is the point at which the sound starts attenuating If the listener is any closer to the source than the minimum distance the sound will play at full volume The maximum distance is the point at which the sound stops attenuating and its volume remains constant a volume which is not necessarily zero 44 Chapter 4 The way volume varies between the minimum and maximum distance is known as the rolloff model By default FMOD uses a logarithmic rolloff that attenuates volume as a proportion of the minimum distance
102. rs and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals However Packt Publishing cannot guarantee the accuracy of this information First published August 2013 Production Reference 1190813 Published by Packt Publishing Ltd Livery Place 35 Livery Street Birmingham B3 2PB UK ISBN 978 1 84969 909 9 www packtpub com Cover Image by Suresh Mogre suresh mogre 99 gmail com www allitebooks com Credits Author David Gouveia Reviewers Tomas Pettersson Daniel Varela Acquisition Editor Edward Gordon Commissioning Editor Shreerang Deshpande Technical Editors Larissa Pinto Nitee Shetty Project Coordinator Suraj Bist Proofreader Lesley Harrison Indexer Tejal Soni Graphics Abhinash Sahu Production Coordinator Melwyn D sa Cover Work Melwyn D sa www allitebooks com About the Author David Gouveia is a Software Engineer and Game Developer from Portugal Madeira Island He recently finished his MSc in Computer Science with a specialization in graphics and multimedia and is currently working full time as a game programmer for a local company He runs an educational blog about game development and enjoys sharing his knowledge with the community whenever possible Hi
103. s a great car engine simulation that we can study That sound event has two layers and two parameters one for the engine s rpm and one for the engine s load Each of the layers contains four different sounds recorded from a car engine at different rpm ranges The sounds on the top layer correspond to the car accelerating on load while the sounds on the bottom layer correspond to the car decelerating off load The load parameter serves to blend between both layers at runtime with a volume effect When the load parameter is in the middle we hear a mix of both layers but as the load parameter changes the volumes quickly change so that we only hear one of the layers 66 Chapter 5 The rpm parameter serves two purposes As the primary parameter it determines which of the four sounds should be playing for the current value The sounds actually overlap at the edges so at certain rpm values we can hear a mix of two sounds at once The other purpose of the rpm parameter is to modify the pitch of the sound so that higher the rpm value the higher is the pitch of the sound This is handled automatically by enabling the auto pitch feature on each of the sounds 0 000 0 7100 0 200 0 300 0 4000 0 500 0 600 o 700 0 600 0 900 i Enginesonmid Engine anhigh fEnginesofFlow Mi iEnginejoffmid fEnqineorFhigh Creating a complex ambient track of a forest Using a simple event we were able to create a looping ambient track with
104. s main interests in game development are graphics and audio programming He also has a strong interest in music and synthesizers having played the keyboard most of his life www allitebooks com About the Reviewers Tomas Pettersson is a creator of the freeware audio tools SFXR and Musagi Daniel Varela was born in Trebujena Spain in 1980 His strong passion for music and technology led him to obtain a Bachelor s degree in Sound and Image Engineering from the University of Malaga Spain in 2004 From very early on in his education he focused on digital audio signal processing designing and developing software simulations for audio signals quantification noise modeling experimental reverb effects and culminating in an application for the digital audio editing as his final project of studies After graduating he worked for six years in the software consultancy area as an Applications Programmer and Analyst During this stage he improved his Object Oriented Programming skills and working methodology but however he felt like something was missing In 2010 he joined TheGamekKitchen a just born indie videogames development company as a Generalist Programmer During this period he made familiar game engines such as XNA or Unity3D and developed some audio application prototypes such as a MOD tracker player for XNA or a scratching application for Windows Phone In 2011 he started working at BlitzGamesStudios in the UK as Audio Pro
105. s still a one to one relationship between the sound and the audio file However a sound does not necessarily correspond to a single audio file In many scenarios we can benefit from using multiple audio files for a single sound For example we can often reduce repetition by providing several variations of the same sound as separate audio files or we can build complex soundscapes by combining several smaller sound fragments For other sounds the modifications we apply at runtime to their parameters are just as important as the audio files that compose them For example we cannot realistically simulate the sound of a car engine without constantly updating its pitch and volume based on the engine s rpm and load values Another common example is to have a soundtrack dynamically react to the events in the game in order to convey more or less tension to the player As programmers we could certainly implement any of these features by writing specialized code for each situation orchestrating each audio file and sound parameter as necessary However this approach takes a significant amount of effort and is hard to manage and tweak since most of the behavior gets hardcoded into the game An even bigger problem is that it is usually a sound designer not a programmer which creates the sounds for a game and using this approach would require a significant amount of communication and synchronization between both parties Thankfully we can solve this
106. s used by the industry nowadays Additionally other game development topics such as graphics physics or artificial intelligence tend to be more enticing to beginner level game developers and learning about audio becomes less of a priority The main goal of this book is to give you a crash course on audio programming for games by using a popular and well established audio engine and covering the subject from several different levels of abstraction It is my hope that this approach will give you enough knowledge to implement most of the audio features that are normally required for a video game and form a foundation so that you may pursue other topics that are more advanced What this book covers Chapter 1 Audio Concepts covers some of the most important audio concepts such as sound waves analog and digital audio multi channel audio and audio file formats Chapter 2 Audio Playback shows how to use FMOD to load and play audio files and how to begin creating a simple audio manager class Chapter 3 Audio Control shows how to control the playback and parameters of a sound and how to group sounds into categories and control them simultaneously Chapter 4 3D Audio covers the most important concepts of 3D audio such as positional audio reverberation obstruction occlusion along with a few DSP effects Chapter 5 Intelligent Audio provides an overview of high level sound design using the FMOD Designer tool with examples of h
107. t 35 Audio Control float RandomBetween float min float max if min max return min float n float rand float RAND MAX return min n max min Stopping all sound effects from playing is trivial to implement thanks to the channel groups You would typically call this when changing between scenes or opening a menu void AudioManager StopSFXxs groups CATEGORY SFX gt stop Playing and stopping songs Songs are a bit harder to handle because we only want one to be playing at all times and we want transitions between them to happen smoothly FMOD does not provide a way to fade the volume between sounds automatically so we have to implement this manually with setVolume calls within the Update method First we need to create some member variables to store some states FMOD Channel currentSong std string currentSongPath std string nextSongPath enum FadeState FADE NONE FADE IN FADE OUT FadeState fade From the top we need the channel handle to update the volume of the song the path of the current song to ensure that we do not play the same song again and the path of the next song to start playing it after the previous one finishes fading out We also need a variable to store if we are currently fading in or fading out The PlaySong method follows these rules e If we are trying to play a song that is already playing nothing should happen e If weare trying
108. t and calculate sample count PCM16 pcmData PCM16 data int pemDataCount length 2 Tell the channel to write to the output channel WriteSoundData pcmData pcmDataCount return FMOD Ok 82 Chapter 6 Notice that in the preceding example we begin by clearing the audio buffer with memset This is necessary because we will not be filling the output with values once the sound stops playing and FMOD does not clear the buffer automatically between callback calls Playing a sound with this architecture is as simple as instantiating the sound and asking the channel object to play it MySound sound new MySound explosion wav channel Play sound Pausing a sound Now that we have the basic functionality for playing sounds implemented using the MySound and MyChannel classes we can begin adding more features to it We will start with the simplest of all pausing the sound We must add a member variable to hold the pause state and some methods to modify it We must also remember to initialize this value to false inside the constructor and inside the Play method public bool GetPaused const return paused void SetPaused bool value paused value private bool paused Next all we have to do is add a very simple condition at the beginning of the WriteSoundData method so that it does nothing when the sound is paused That is as simple as it gets void MyChannel WriteSoundData PCM16 d
109. tch and vice versa We could choose frequency values arbitrarily to get the desired effect but an easier way to deal with pitch is in musical terms In musical theory the difference between two pitches is called an interval with two of the most basic types of intervals being the octave which corresponds to the distance between two consecutive notes with the same name and the semitone which corresponds to the distance between any two adjacent notes The following are a few simple rules we can modify an existing frequency by any of these intervals e Every time we multiply divide a frequency by two we get a new frequency that sounds one octave higher lower e Every time we multiply divide a frequency by two and a half we get new a frequency that sounds one semitone higher lower To make things easier here are two helper methods that perform the previous calculations given a frequency and the number of octaves or semitones to change Notice the use of the pow function to apply the previous multiplications and divisions the necessary amount of times include lt math h gt float ChangeOctave float frequency float variation Static float Octave ratio 2 0 7 return frequency pow octave ratio variation float ChangeSemitone float frequency float variation Static float semitone ratio pow 2 0f 1 0 12 0 return frequency pow semitone ratio variation 28 Chapter 3 Using these helper me
110. tem Initialize the event system and load the project eventSystem gt init 100 FMOD INIT NORMAL 0 FMOD EVENT INIT NORMAL eventSystem gt load project fev 0 0 Update event system every frame eventSystem gt update Release event system when we are done eventSystem gt release In order to play an event we must get a reference to it by using the fully qualified name of the event which contains the project name the name of the event group that contains the event and the name of the event itself Then we can simply use the start method to play the event Get a reference to the event FMOD Event event eventSystem gt getEvent ProjectName EventGroupName EventName FMOD EVENT DEFAULT amp event Begin playing the event event gt start Finally if there is a parameter that we want to modify we can get a reference to it using the getParameter method of the event object and change the value using the setValue method of the parameter object Get a reference to the parameter FMOD EventParameter parameter event gt getParameter ParameterName amp parameter Change the value of the parameter parameter gt setValue 2 0 70 Chapter 5 Summary In this chapter we have seen how a sound can be a lot more than just an audio file how FMOD has a high level tool called the FMOD Designer how we can create simple and multi track sound events in the
111. the set 3DAttributes method The range of the reverb is specified with a minimum radius reverb is at full volume within that radius and a maximum radius reverb is disabled outside that radius FMOD VECTOR position 10 0f 0 0f 0 0f reverb gt set3DAttributes amp position 10 0f 20 0f Setting the default ambient reverb We can also set which reverb properties to use when the listener is not inside any reverb zone using the setReverbAmbientProperties method of the system object FMOD REVERB PROPERTIES properties FMOD PRESET OFF system gt setReverbAmbient Properties amp properties Obstruction and occlusion Obstacles in the environment such as large objects or walls also alter the way we perceive sound We can often hear a person speaking in an adjacent room but the sound is not as clear as if they were standing next to us The reason for this is that although sound can pass through several types of materials it loses energy and several of its higher frequencies during the process This results in a quieter muffled sound There are two techniques used to simulate obstacles in 3D audio obstruction and occlusion Obstruction occurs when the source and the listener are in the same environment and there is an obstacle in the way but there is still enough space around the obstacle for the sound waves to flow In this situation sound waves passing directly through the obstacle are attenuated and filtered but refle
112. the sound and our ears has a significant effect on its intensity because air and other mediums attenuate sound as it passes by e Direction Our ears can identify the direction a sound is coming from thanks to minor time and intensity variations between the sounds captured by each ear e Movement The relative speed between the sound source and our ears can make it appear to have a different pitch because of a phenomenon known as the Doppler effect e Room The size and shape of the room we are in can cause multiple echoes to accumulate producing a reverberation effect where sound seems to persist temporarily even after the original sound has stopped e Obstacles Obstacles between the sound source and our ears tend to attenuate and muffle the sound This is particularly true in the case of large obstacles such as walls 3D Audio In this chapter we will explore the basics of 3D audio which is the field of audio programming that tries to take some or all of these factors into consideration in order to produce a realistic audio simulation This is one of the areas where using an audio engine such as FMOD really pays off as it would be extremely difficult to implement some of these features ourselves Positional audio The first aspect of 3D audio that we are going to work with and perhaps the most important is positional audio Positional audio deals primarily with the location of each object that produces sound which we will r
113. thods it becomes simple to modify the pitch of a sound in FMOD in a meaningful way For example to decrease the pitch of a sound by 3 semitones we could do the following float frequency channel gt getFregquency amp frequency float newFrequency ChangeSemitone frequency 3 0f channel gt setFrequency newFrequency Note that changing the frequency of the sound will also have the side effect of speeding it up or slowing it down There is a way to change the pitch of a sound without affecting its speed in FMOD but it requires using a DSP effect which is outside the scope of this chapter We will briefly cover DSP effects in the next chapter Controlling the panning Finally we can also control the panning of some sounds as long as they are mono or stereo and 2D as the FMOD engine automatically positions 3D sounds When these conditions are met you can change the panning of the sound using the set Pan method which takes any value from 1 completely on the left to 1 completely on the right Channel gt setPan 1 0 Panning works by modifying the volume of each output to give the illusion of position However the way FMOD calculates these values is different between mono and stereo sounds For mono sounds the volume of each speaker follows a constant power curve that starts at 0 percent on one side and goes to 100 percent on the other side with the center position being at around 71 percent This techni
114. ti The class contains quite a few more members than the SimpleAudioManager class but the basis is the same To summarize the differences we now have public methods to load play stop and control the volume of sound effects and songs separately Then in the private portion of the class we have an enumeration with the types of categories and arrays of channel groups sound maps and modes containing enough entries for each of the categories Finally there are some variables required to handle transitions between songs Initialization and destruction In the constructor besides initializing the sound system we create one group channel for each sound category and add them to the master channel group We also initialize an array of modes describing how sounds in each category should be loaded Finally we seed the random number generator that will be used to play sound effects AudioManager AudioManager currentSong 0 fade FADE NONE Initialize system FMOD System Create amp system system gt init 100 FMOD INIT NORMAL 0 33 Audio Control Create channels groups for each category system gt getMasterChannelGroup amp master for int i 0 i lt CATEGORY COUNT i system gt createChannelGroup 0 amp groups i master gt addGroup groups i Set up modes for each category modes CATEGORY SFX FMOD DEFAULT modes CATEGORY SONG FMOD DEFAULT FMOD CREATESTREAM
115. to play a song but another song is already playing we cannot start immediately Instead we instruct the manager to begin stopping the current song and store the path of the song to play afterwards 36 Chapter 3 e If no song is playing we can start the new song immediately with its initial volume set to zero and the manager set to the fade in state The song must also be added to the correct channel group void AudioManager PlaySong const std string amp path Ignore if this song is already playing if currentSongPath path return If a song is playing stop them and set this as the next song if currentSong 0 StopSongs nextSongPath path return Find the song in the corresponding sound map SoundMap iterator sound sounds CATEGORY SONG find path if sound sounds CATEGORY SONG end return Start playing song with volume set to 0 and fade in currentSongPath path system gt playSound FMOD CHANNEL FREE sound gt second true amp currentSong currentSong gt setChannelGroup groups CATEGORY SONG currentSong gt setVolume 0 0f currentSong gt setPaused false fade FADE IN e The StopSongs method is significantly easier to implement as it only needs to trigger a fade out if a song is playing and clear any pending song request that was previously set void AudioManager StopSongs if currentSong 0 fade FADE OUT nextSongPath clear
116. tone Microsoft XNA 4 0 Game Development Cookbook Unity Game Development Essentials ISBN 978 1 84719 818 1 Paperback 316 pages Build fully functional professional 3D games with realistic environments sound dynamic effects and more 1 Kickstart game development and build ready to play 3D games with ease 2 Understand key concepts in game design including scripting physics instantiation particle effects and more 3 Test amp optimize your game to perfection with essential tips and tricks Microsoft XNA 4 0 Game Development Cookbook ISBN 978 1 84969 198 7 Paperback 356 pages Over 35 intermediate advanced recipes for taking your XNA development arsenal further 1 Accelerate your XNA learning with a myriad of tips and tricks to solve your everyday problems 2 Get to grips with adding special effects virtual atmospheres and computer controlled characters with this book and e book 3 A fast paced cookbook packed with screenshots to illustrate each advanced step by step task Please check www PacktPub com for information on our titles PACKT PUBLISHING AndEngine for Android Game Development Cookbook T CryENGINE 3 Cookbook AndEngine for Android Game Development Cookbook ISBN 978 1 84951 898 7 Paperback 380 pages Over 70 highly effective recipes with real world examples to get to grips with the powerful capabilities of AndEngine and GLES 2 1 Step by step detailed instructions
117. track of the current position within the sound that is how many samples we have written so far so that we know which sample to write next Once the position becomes larger than the number of samples in the data it means that the sound has finished playing and we interrupt the process 80 Chapter 6 Like we did with the sound class let us also create a class to encapsulate all of the data and behaviors related to playing sounds which we will name MyChannel class MyChannel public MyChannel sound 0 position 0 void Play MySound mySound void Stop void WriteSoundData PCM16 data int count private MySound sound int position 13 Like the channels in FMOD we should be able to reuse a single channel object for different sounds Therefore instead of taking a sound object in the constructor we only assign the sound object inside the Play method This method also resets the position value void MyChannel Play MySound mySound sound mySound position 0 The Stop method on the other hand simply clears the reference to the sound object void MyChannel Stop sound 0 Finally the most important portion of the process occurs inside the WriteSoundData method which will be called from within the audio callback This method takes two parameters the array of PCM samples to write to and the size of this array Notice that this method already expects the data array to
118. tstep sounds for all different types of surfaces such as grass concrete or sand and allow the game to control the walking speed through a parameter In order to do this we must first create a sound def for each type of surface the character can walk on Each sound def should play a footsteps sound loop at the average walking speed which we can control with the spawn rate parameter this speed should be consistent between each sound def Then we must create a multi track event with a single layer and two parameters to control the surface type primary and the walking speed By adding all the sounds to this layer distributing them evenly by right clicking and selecting the Layout sounds evenly option and setting the maximum range of the surface type parameter to be the total number of sounds in the layer we can use that parameter as a simple index to select which surface the character is walking on For the walking speed parameter we need to add an effect of type Spawn Intensity to the layer and draw a curve to control how the spawn intensity relates to the walking speed parameter For example a value of 0 5 means that the footsteps will occur at half the average speed while a value of 2 0 means that footsteps will occur at twice the average speed Simulating the sound of a car engine We can also use multi track events to generate complex interactive sounds such as the sound of a car engine The FMOD Designer examples project ha
119. w much we should advance the phase between each sample and volume which can be changed through the Set Volume method Note that we are using doubles for everything instead of floats as sound synthesis tends to require more precision in its calculations All that the class constructor does is initialize the phase to zero the volume to one and set the increment by calling SetFrequency witha default value of 440 Hz MyOscillator MyOscillator phase 0 0 volume 0 5 SetFrequency 440 0 The SetFrequency method calculates the correct increment value using the following formula In this case we have hardcoded the sampling rate to be 44100 Hz but there could be a parameter to control the sampling rate void MyOscillator SetFrequency double frequency increment frequency 44100 0 TWO PI 93 Low level Audio As usual most of the work is handled inside the WriteSoundData method First we calculate the value of the sound wave for the current phase and scale it into the correct range for a PCM16 sample by multiplying by 32767 which is the highest number that can be stored in a signed short Next we write this result to the audio output mixing it with anything that was already there Finally we increment the phase and wrap it so that it always stays within the 0 to 2 PI range void WriteSoundData PCM16 data int count for int i 0 i lt count i 2 4 Calculate sample value double value
120. xample code files for all Packt books you have purchased from your account at http www packtpub com Q If you purchased this book elsewhere you can visit http www packtpub com support and register to have the files e mailed directly to you Besides that reason FMOD is also an excellent piece of software with several advantages to game developers e License It is free for non commercial use and has reasonable licenses for commercial projects e Cross platform It works across an impressive number of platforms You can run it on Windows Mac Linux Android iOS and on most of the modern video game consoles by Sony Microsoft and Nintendo e Supported formats It has native support for a huge range of audio file formats which saves you the trouble of having to include other external libraries and decoders e Programming languages Not only can you use FMOD with C and C there are also bindings available for other programming languages such as C and Python e Popularity It is extremely popular being widely considered as the industry standard nowadays It was used in games such as BioShock Crysis Diablo 3 Guitar Hero Start Craft I and World of Warcraft It is also used to power several popular game engines such as Unity3D and CryEngine e Features It is packed with features covering everything from simple audio playback streaming and 3D sound to interactive music DSP effects and low level audio programming
121. xt menu or using the dial control at the bottom left corner of the pane Playlist Sound 500 bird call01 ogg 25 00 bird call02 0gg 2500 bird call03 ogg amm bird calld4 ogg On the Playlist Options pane we can control how the audio engine should pick files from the playlist There are three different Playlist Behaviors e Random This option picks an audio file at random every time following the weights attributed in the playlist to each of them We can also select whether to allow the same audio file to play twice in a row e Shuffle This option randomizes the playlist once and then plays the audio files in that order e Sequential This option follows the same order in which the audio files appear in the playlist Inside the Playlist Options pane we can also find a Sound Randomization section which lets us apply some variation to the starting volume and pitch of each file similar to what we implemented ourselves back in Chapter 3 Audio Control Playlist Options Playlist Behavior Random Shuffle Sequential Allow sounds to be repeated Allow silences to be repeated Sound Randomization Attenuation 0 dB Pitch 0 s tones 58 Chapter 5 In the Playback Options pane which controls how many audio files should be played and how often there are four different Playback Modes e Oneshot This mode picks a single audio file and plays it only once e Repeating Loop This mode picks a sin
122. y run approx 60 times per second float elapsed clock getElapsedTime asSeconds if elapsed lt 1 0f 60 0f continue clock restart sf Event event while window pollEvent event 23 Audio Playback Handle window events if event type sf Event Closed window close Handle user input if event type sf Event KeyPressed amp amp event key code sf Keyboard Space audio Play explosion wav Place your update and draw logic here audio Update elapsed Place your shutdown logic here return 0 Summary In this chapter we have seen some of the advantages of using the FMOD audio engine We saw how to install the FMOD Ex Programmer s API in Visual Studio how to initialize manage and release the FMOD sound system how to load or stream an audio file of any type from disk how to play a sound that has been previously loaded by FMOD how to check for errors in every FMOD function and how to create a simple audio manager that encapsulates the act of loading and playing audio files behind a simple interface 24 Audio Control In the previous chapter we saw how to load and play audio files in FMOD This time we will explore some of the ways in which we can control the playback of those files We will start with controlling the playback flow by stopping the sound on demand or seeking to different points in the audio file Then we will cover how to modify the mai

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