Aliki - 0.0.1 User Manual
Contents
1. Aliki 0 0 1 User Manual Aliki 0 0 1 aliki Session Load Save impot Export Sweep Capture Convol Edit Integr 20 30 20 30 1 1 1 1 1 1 0 0 2 0 nau vi z gt 2 3 I 1 1 U 1 8 0 10 0 Mi Lin Log Aliki s Contents 1 Introduction 3 1 1 Installation s ios pe one kad gok o waw W de oe Ge O a e de ke 3 1 2 Running A liki sa seica a hae bole a eR ee ee ge de E W s are HA 6 3 13 Whe Aliki file format psoe ecs we eo emos rewia WWE dog bel ev ee 4 1 4 C TThesessiondirectory 4 2 Viewing waveforms 5 3 The sweep generation window 7 4 The capture window 8 4 1 Inputs and outputs L La a aa ea 8 4 2 Measurement parameters 9 4 3 Performing the measurments 9 5 The convolution window 10 6 The editing window 11 7 Importing and exporting 13 7 1 Importingsoundfiles 13 7 2 Exporting ald files s wa ae wal hase ao WAW ge obe ve O W pe Ri okvi TE W 13 Fons Adriaensen 2 Aliki s 1 Introduction This is the user manual for the first alpha release of Aliki This release is basically the same program as demonstrated at LAC2006 just cleaned up a bit Many features are still missing as is for example any decent form of error reporting As I m still searching for the right mod2. O Fons Adriaensen 3 Aliki s Most of this will be clear enough but the E option may need some comments The audio interface part of Aliki is a separate executable aliki rt which is started by the main program if an audio interface is reguested on the the command line A or J The two parts communicate via shared memory The main reason for this separation is to avoid JACK locking all the memory blocks used by the processing code These could be quite large there is no need to lock them and doing so could easily deplete physical memory on some systems It is preferable to run aliki rt with real time privileges How this is done depends on your system On some systems nothing special is required On others aliki rt needs superuser status in order to be able to run in real time mode and this may require a prefix command such as sudo or rtlimits The E option allows to specify such a prefix Aliki does not depend on low latency latency can be compensated for later so you may use larger period sizes than would be required for interactive audio work Note that it is possible to run Aliki without any audio interface at all for example to process previously captured files 1 3 The Aliki file format Aliki uses its own file format with the filename extension ald The same file format will be used by some other applications in development that use impulse responses An ald file is a multi channel multi section audio file using
3. This is used to deconvolve the recorded sweeps and obtain the impulse response s Use Load in the main window to load a capture file before selecting the convolution function Es Aliki 0 0 1 aliki x Start time 1 Sweep w he fons aliki test sweep logsweep10 ald Apply End time 6 Save Cancel o 30 60 Ae nada Figure 4 Convolution controls Start time and End time are relative to the position where the impulse response would start without any audio latency and delay A negative Start time can be used when using a log sweep to see the harmonic distortion of the system being tested each harmonic will show up as a separte IR at some place in negative time depending on the sweep rate The End time should be set in function of the expected impulse length A good value is the expected reverb time plus two or three seconds The Sweep file should of course be the same one as used during the measurement When all parameters are set click Apply to start the deconvolution on the current section This may take a few seconds there is no progress bar yet but it will be added in future releases The result will be displayed and you can zoom in scroll etc but not yet stored For a multi section file moving between sections will start the deconvolution of the next or previous section Again this may take some time When the parameters seem OK the deconvolution can be done for all sections and the results saved by clickin
4. multi channel ald files are split into separate WAV files Click Export and fill in a name without the extension A channel suffix and the extension will be added automatically The option to export all sections in a single operation will be added in a future version Fons Adriaensen 13
5. will correspond to a new section in the capture files e Idle time is the time in seconds between two measurements i e the time reguired to rotate a speaker move a microphone or whatever Nothing will be recorded during this time At the end of the idle time the next sweep playback and the recording of the next section of the capture files will start simultaneously e Trigger command can be any external program It is executed at the start of the idle time after each measurement and can be used for example to trigger a rotating table to move to the next position 4 3 Performing the measurments The buttons in the lower right corner control the actual measurment A Test signal an FM modulated sine can be output to adjust levels before a measurement The test output is at 15 dB and should result in about the same level returning on the inputs The actual sweeps will be at 6 dB so this should be taken into account when setting up the levels using the test tone The measurement is started using the Start button The Trig button will flash at the start of the idle time after each measurement If you perform an automatic sequence using multiple sources this is the right time to switch them The measurement sequence is finished when the Start button lights again It can be terminated at any time using Stop In that case any partially recorded capture files will be deleted Fons Adriaensen 9 Aliki 5 The convolution window
6. el that will encompass all planned features in an un derstandable and easy to use structure future versions of Aliki may be guite different from this one But it works and it can be used for practical work 1 1 Installation Compiling and installing Aliki should be simple enough Unpack the source tarball cd to it then make and as root make install The default install directory is usr bin To change this just edit the PREFIX variable in the Makefile Alike depends on a number of shared libraries These are e libclthreads version 2 2 0 1 or later e libclalsadrv version 1 1 0 1 or later e libclxclient version 3 3 1 or later e libsndfile any recent version e libfftw3f any recent version The first three are available from the same place as the Aliki sources The last two come with all Linux distributions It may be worth the effort to compile the fftw3f library locally using optimisation options e g enabling SSE adapted to your platform 1 2 Running Aliki Running aliki h will show the command line options Aliki 0 0 1 C Fons Adriaensen lt fons adriaensen skynet be gt h Display this text J Use JACK A Use ALSA with options d lt device gt Alsa device hw 0 0 r lt rate gt Sample freguency 48000 p lt period gt Period size 1024 n lt nfrags gt Number of fragments 2 E lt prefix gt Prefix for audio process e g sudo Without either J or A only the processing functions are available
7. g Save It is not necessary to have moved through all sections before as everything will be recomputed anyway The resulting file is stored in the IMPRESP subdirectory of the session and also becomes the currently loaded file Clicking Cancel will return to the main window without storing anything The capture file remains the current file in that case Fons Adriaensen 10 Aliki C 6 The editing window This function is used to prepare IR for practical use Enter this window with an IR file from the IMPRESP directory loaded ol Aliki 0 0 1 aliki x 0 088000 Timeref 0 036000 0 007000 Trim start 1 0 Normalise Trim end Save Cancel 0 10 20 30 bi IM Figure 5 Editing controls Four operations are provided All of them are non destructive until the result is saved They can be also be repeated any number of times and be can be undone by R clicking the corresponding button e Setting the reference time This will not normally be necessary but is provided to be used while preparing files for another application which needs this It can also be useful just to align the time axis while examining an IR Put a single marker at the place that should correspond to zero time zoom in to set it precisely L click Time Ref to move the time axis so it becomes zero at the marker position e Amplitude normalisation Put a single marker on the direct sound peak of the IR zoom in to set it prec
8. isely L click Normalise to normalise to unit energy in a small region around this point e Trimming the start This normally used to remove any debris before the start of the IR or to remove the direct sound or even some early reflections Put two markers at the times where you want a raised cosine fade in to start and reach unity gain respectively then L click Trim start e Trimming the end This normally used to remove the noise tail at the end of an IR Put two markers at the times where you want a raised cosine fade out to start and reach zero gain respectively then L click Trim end When moving between sections of a multi section file the currently active settings are apllied to each newly displayed section When the result is saved the current values are applied to all sections of the file so relative timing and gain are preserved The signal parts before the fade in and after the fade out are removed The output file will be put into the EDITED subdirectory of the session and also Fons Adriaensen 11 Aliki s become the currently loaded file Cancel will terminate the editing without storing anything and keep the current file Fons Adriaensen 12 Aliki s 7 Importing and exporting 7 1 Importing sound files This is not implemented in the current version 7 2 Exporting ald files The currently loaded file can be exported to floating point WAV format Each section should be exported separately and
9. le from the list use the Remove option in the file type menu The sweep file to be used can be selected from the SWEEP directory Make sure to select one with the correct sample rate this is not checked in the current release Using the wrong sample rate will work but the frequency range will be shifted Future versions will allow a loudspeaker equalisation file to be selected from the SWEEP directory and also provide a function to compute such files This is currently not implemented Any mix of up to eight output channels can be selected by the buttons 1 8 In most cases a single source will be used for IR measurment Fons Adriaensen 8 Aliki s 4 2 Measurement parameters Below the output selection buttons are the fields that control the actual capture operation e Sweep time is filled in from the sweep file and can not be changed e Capture time sets the length of the recorded signals in seconds It should be at least equal to the sum of sweep time audio latency expected IR length time and some safety margin Aliki allows to automate sequences of measurements using the same paramters for example when measuring the polar diagram of a speaker This feature can also be used to record a set of IR using a sequence of different sources In this case the output switching must be done manually this will be automated as well in later versions e Iterations is the nunber of automatically sequenced measurments Each of them
10. lse response To set a marker R click in the display area at the place where you want to put a marker To move a marker L drag it by the square near the top When a marker is set this is indicated by one of two buttons lighting up in the corresponding color and showing an arrow instead of a square The arrow indicates where the marker is up if it is on screen left or right if a marker is set but not visible When a marker is set then an L click on the corresponding button scrolls the display to the marker position so that it is put at the centre An R click on a marker button will erase the marker if it is on sceen or bring it on screen otherwise The previous position is lost in both cases This can be handy when you want to re use an existing marker that has gone off screen The and buttons to the right control the horizontal scale factor i e they zoom in or out L click moves one level up or down R click goes faster Fons Adriaensen 5 Aliki i The zoom focus is the most recently referenced marker if still set and visible or the centre of the display area otherwise In other words when you go to a marker clicking its button or when you move it it also becomes the zoom focus The Lin and Log buttons select either a linear or logarithmic vertical scale The and buttons on the right margin modify the vertical scale For the linear format they just change the scale factor For the logarithmic one they modify the l
11. ontinuity at the end Note that the frequency will continue to move up during the fade out so this should be short to avoid going above half the sample frequency in some cases When all parameters are filled in click the Create button to generate the sweep Fons Adriaensen 7 Aliki 4 4 The capture window This window will be available only if Aliki was started with an audio interface option A or J It controls all aspects of the actual IR measurement operation Aliki 0 0 1 aliki Capture 30 20 15 10 6 3 0 Capture files v W bformat X W Z v L stereo R r v 30 20 15 10 6 3 0 Sweep file fons alikitest sweep logsweep10 ald Equal file v Output channel 1 2 3 4 5 6 7 8 Es Capture Stop Start Capture time 15 0 Iterations 1 o Test idle ime 1 0 Trigger command Trig Figure 3 The capture window 4 1 Inputs and outputs The top left part of this window fig 3 shows the level meters for each input channel To the right of these are the controls to set file names and types for the recorded sweeps An L click on any of the arrow buttons besides the level meters will bring up a menu of available file types Select the number of channels and type you need The input channels will be labeled accordingly and a text input field for the file name will appear Recorded files will be stored in the CAPTURE subdirectory of the session To remove an input fi
12. ower limit of the displayed range Fons Adriaensen 6 Aliki s 3 The sweep generation window A sweep file is a single section two channel ald file The first channel contains the forward sweep with rising freguency used by the capture function The second channel is the in verse sweep used for deconvolution The convolution of these two will always be a Dirac pulse bandlimited to the freguency range of the sweep ri Aliki 0 0 1 aliki Sweep x Name logsweep10 Rate 48000 Fade in 0 Start freq 20 Sweep time 10 Type Lin Log End freq 20e3 Fade out 001 Create _Close Figure 2 The sweep generator window The following parameters fig 2 should be filled in to generate a sweep e Name filename without the ald extension The file will be put into the SWEEP subdi rectory of the session e Rate the sample rate This will be filled in if the audio interface is active otherwise type in the required value e Fade in a soft fade in can be speficied The parameter is the time in seconds It is normally not required as the generated sweep will always start at a zero crossing e Start freq the lower limit of the frequency range in Hz e Sweep time the sweep time in seconds e Type either linear or logarithmic e End freq the upper limit of the sweep range in Hz e Fade out a fade out time in seconds after the upper frequency limit has been reached This is used to avoid a disc
13. single precision floating point as the sample format Apart from the audio signals some other information is stored For example special formats such as Ambisonics B format or MS stereo can be identified and treated correctly even if they have the same number of channels as some other formats All files used by Aliki can be exported to WAV format for external use Future versions will also allow conversion of external files to the ald format 1 4 The session directory The current version of Aliki does not have a real session concept but it does depend on a particular directory structure A session directory should contain at least the following subdi rectories e sweep sweep and equalisation files e capture recorded room responses e impresp raw impulse responses e edited modified impulse responses It is absolutely essential for the current version which lacks decent error reporting that the session directory is set correctly Failing to do so may lead to mysterious failures A new session directory can be initialised from the file window see below To set the session directory click Session in the main window A filer window will open for the current directory To create a new session directory navigate to the place where you want it Use the New dir function to create the directory Then click Session to create the required subdirectories To select an existing session directory navigate to it so you see the required
14. subdirs then click Session Fons Adriaensen 4 Aliki s 2 Viewing waveforms The main window normally displays the waveform s in the currently loaded file if any 20 30 i 1 1 1 1 1 1 1 U 1 1 1 I 1 1 1 1 1 1 0 0 20 40 6 0 10 0 8 0 SC viziji 4v gt 2 3 W Lin Log 1 1 Figure 1 Bottom of main window At the bottom fig 1 are some controls for this waveform display To scroll the display horizontally just L drag the time scale The controls at the left control which part of a file is shown If the file is a multichannel file there will be up to four channel selection buttons The labels depend on the file type in the figure an Ambisonics B format file is shown L click selects a single channel R click adds a channel to the current selection These buttons are not shown if the file only has a single channel If the file has more than one section there will be left and righ arrow buttons selecting resp the previous and next section Again these buttons will be not be shown if there is only a single section The index of the current section and the number of sections are always shown At the right are a set of buttons that control the markers zooming and the vertical scale Up to two markers can be put on the waveform display A marker is a vertical line corresponding to a particular sample offset It is used for various purposes for example when editing an impu
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