SC_downloads_files/Single Mechanical User Manual 4.0
Contents
1. 108 cropped 120 60 20 Hz 1200 Hz Mechanical Progressive Left to Right Top to Bottom 64 8 KHz 100 0 video sync ratio 6 5 120 60 25 Hz 1500 Hz Mechanical Progressive Left to Right Top to Bottom 90 0 KHz 100 0 video sync ratio 29 Available Models Available Models Model No SCM 01 NTSC PAL to 24 20p through 60 25p output standards Model No SCM 01D NTSC PAL to 24 20p through 60 25p output standards with internal current driver 30 Firmware Revision History Firmware Revision History Revision 4 0 October 2 2012 1 New hardware revision based on 4 x hardware now incorporates FPGA firmware factory parameters user parameters and user default image into a single serial FLASH ROM 2 Added 36 10p standard Revision 3 2 March 12 2011 1 Changed behavior of the Black Level control When enabled this forces the black level of all standards to be set to 30 and peak white set to 100 This is used when the internal current driver is used Revision 3 1 December 5 2009 1 Changed behavior of the Reference Input When supplied with a 50Hz or 60Hz input the video output will now adapt it s base frequency to match For instance with a 60 20p standard and a 60Hz reference the video output will be 60 20p and frequency phase locked to the reference If a 50Hz reference is used the output will now be 60 15p and will still be frequency phase locked to the reference This change was made2. S N Ii A LJ CD ROAN _ S aS NI Standards Converter for Mechanical Television Model s SCM User and Technical Manual Copyright 2006 12 Aurora Design LLC Revision 4 0 2 October 2012 All specifications subject to change www tech retro com Introduction Introduction This manual covers the operation and technical aspects of the Single Standard Converter for mechanical television The Converter is designed to accept an NTSC or PAL SECAM video signal and convert to one of several different output standards The converted video is sent to a composite video output connector Due to the nature of mechanical television it is assume that the user has a good understanding of what is required to operate such a device in conjunction with this converter such as an appropriate lamp Neon LED etc and a lamp driver that accepts the video output signal from this converter No attempt is made in this document to describe such a driver and it s operation Features e Compact low power surface mount design e Front panel tri color Status LED e Up to 16 user programmable options e Extremely stable output 3 levels e 10 bit video D A for greater than 54dB dynamic range e 250K gate equivalent FieldProgrammableGateArray e 8Mb FLASH memory for FPGA firmware user parameters and default image e Automatic Sleep Mode for low power standby operation e Reference Input allows synchronization to external source e Extremely accurat
3. and must be set to Enabled when using the optional internal Current Driver Position 7 Reverse Line This option is used to reverse the direction of the scan lines when Enabled For instance the normal direction for the 45 15_31 Western is right to left so this will force left to right scanning 60 20p is left to right so this will force right to left scanning When Disabled the scan lines will be in the normal direction for the Output Standard This can be useful if the television motor operates in the wrong direction or the viewing window is on a different part of the wheel etc This option should normally be set to Disabled Position 8 Reverse Frame This option is used to reverse the scan direction of the frames When Enabled this option will reverse the normal scan direction of a frame For instance the normal direction for the 45 15 31 Western is top to bottom so this will force bottom to top 11 Introduction scanning 30 12 5 Baird is bottom to top so this will force top to bottom scanning When Disabled the frames will be in the normal direction for the Output Standard This can be useful if the television motor operates in the wrong direction or the viewing window is on a different part of the wheel etc This option should normally be set to Disabled Position 9 Reference Edge Polarity This option is used to control which edge the Reference Input Zero Crossing Detector will use When Enable the positive going ed
4. the converter it should remain so indefinitely 15 Introduction Due to the nature of standards conversion frame rate conversion is extremely difficult This converter provides two different methods of frame rate conversion that can be selected by the user More can be found out in the Theory of Operation section later in this manual The use of high quality video cables is recommended for best results Cables conforming to 75 ohm impedance should be used on the video inputs and outputs If all the above steps have been properly performed there should now be a solid yellow or green status light on the front panel of the converter indicating a locked video signal as described previously and a stable image on the television To help aid in setup when no video input is presented to the converter it will output a default image This can be useful in making final adjustments to the television and for phasing the television before the video input is connected Video content is important to consider when dealing with mechanical televisions due to the small size and low resolution of the image Close ups that are centered in the video make for better viewing on the mechanical television For standards with low aspect ratio such as Baird 3 7 and NBTV 2 3 only the center portion of the input video is converted to maintain the correct ratio Some examples of typical connections to mechanical televisions AC Mains To NEL 1M Mains
5. Position 5 Frame Buffer Count This option is used to select between 3 frame buffers and 1 frame buffer When Enable three frame buffers will be used In this mode the output video image will always be complete but fast motion in the video may be jerky or not smooth do to the difference in frame rates between the input video and output video When Disabled only one frame buffer is used which will provide smoother looking images 10 Introduction in the output but images that may have tearing on fast motion For still or slowly moving images both modes will look exactly the same on the output For more information about the this option please refer to the Theory of Operation section found later in this manual This option should be put into the mode the user finds yields the best image quality Position 6 Black Level This option is used to control the Black Level in the output video Some mechanical standards like 32 12 5p NBTV have black level set at 30 with peak white at 100 while most other standards have black at 0 with peak white at 100 This makes it difficult for a lamp driver since the black level and range are different for the various standards To eleviate this condition this option can be Enable which will force all standards to use 30 for black and 100 for peak white making it easier for the lamp driver When Disabled this option will ouput the standards normally This option should be set to Disabled for normal use
6. Reference Western Visionette Example connection to Western Visionette using internal Current Driver 16 Introduction Low pass filter and amplifier To Phonic Coil To Lamp Baird Televisor Example connection to Baird Televisor using external lamp driver and phonic coil filter and power amplifier SCM 01D Current Driver Output When using the Current Driver Output of the SCM 01D converter a few things need to be considered Since this is a linear driver excess heat may be generated in the converter The unit is fully protected against thermal overload and will shut off the output if it reaches 65 C internally and will not return to operation until the temperature falls back below 55 C To minimize heat dissipated by the driver the voltage used to operate the converter should be no more than 2 volts above what is required by the LED you are using when driven at 333ma For example the NEL 1M requires approximately 10 volts to operate at 333ma so you would run the converter at 12 volts maximum Conversely you do not want to use too low of a voltage or clipping may occur in the output spoiling the image It is recommended to keep the input voltage at least 1 volt above the operating voltage of the LED 17 Introduction Theory of Operation In order to convert between different video standards spatial and temporal correction are required Spatial correction involves changing the resolution size and aspec
7. top half of the frame and a linear ramp on the lower half There is also an X in the middle of the 13 Introduction image to help align the image on the television and find the correct sequence for interlaced standards The image appears as below Sleep Mode Since no power switch is supplied on this unit an automatic Sleep Mode will be entered whenever the video input is not present for more than 1 hour With this feature the converter is placed into a low power mode along with the video output being shut off Only the video decoder is left active to signal when a valid video input is again supplied to the unit to wake it up Typical Connections In normal usage a user supplied power adapter is connected to the converter and to the AC power source A valid NTSC or PAL SECAM video source will also be connected to the Composite Video input The video source can be anything from a VCR to a DVD to an off air broadcast The video output can then be connected to the input of a user supplied lamp driver or the output of the optional internal Current Driver can be connected directly to an LED lamp like the NEL 1M A user supplied driver needs to take the video output signal from the converter and power the desired lamp Neon LED etc The users driver should provide for brightness level and contrast gain controls to adjust the video signal for proper operation of the lamp The brightness control can be used to properly setup
8. typical back and forth motion of the image If this occurs either a cleaner reference signal is required or the user can change the Reference Fast Tracking option discussed later The polarity of the edge Introduction used is also selectable by the user as discussed later The input can withstand up to a 30V maximum signal without damage This signal will usually be provided by a small AC transformer typically 6 12Vac plugged into the same Mains outlet as the television or from a frame reference signal supplied by some modern experimental mechanical televisions Rear Panel The rear panel is shown below Current Video Driver 7 14Vdc Output Optional Input Selector Switch Options Button Aux Button Video Output This RCA or BNC connector provides the video output from the converter This output should terminate into a 75 ohm load For complete information about the characteristics of this output please refer to the Specifications section found later in this manual Selector Switch The dual purpose Selector Switch is used to select the output standard and to select the user option during options programing During normal operation the Selector Switch selects the Output Standard of the video output The specific Output Standard for each position can be found on the 6 Introduction bottom label of the converter and in the Supported Output Standards section found later in this manual This control is adjusted by in
9. Driver optional This connector provides a Current Driver output from the converter This output is suitable for direct connection to an LED lamp such as the NEL 1M It is thermally and short circuit protected If the output does go into thermal overload the front panel Status LED will indicate this and the unit will return to normal operation once the temperature has returned to an acceptable level For complete information about the characteristics of this output please refer to the Specifications section found later in this manual Introduction Auxiliary Button The Auxiliary Button is used to frame the image on the television and to store the user default image While most mechanical televisions provide some means to align the scan lines many do not offer such ability for frame alignment By momentarily depressing this button the image will move down by one line By holding this button down for 1 2 seconds the image will move up by one line To store a default image the converter must be in it s normal operating mode with a valid video input connected and a solid yellow or green Status LED If a valid video input is not connected an image cannot be stored With a stable stationary video input applied the Auxiliary Button may be pressed and held for 4 seconds The Status LED will begin to flash yellow or green quickly indicating storing of the image FLASH is taking place This process can take up to 10 seconds and the video
10. be added to the output When Disabled straight video will be output and gamma correction will need to be provided externally This option should normally be set to Enabled 9 Introduction Position 2 Invert This option is used to select the output mode of the converter between normal and inverted When Disabled the converter will output a positive video signal When Enabled the converter will invert the output This can be useful to match the polarity of an external lamp driver This option should normally be set to Disabled Position 3 Default Image Select This option is used to select the default image that is displayed when no video input is present When Disabled the built in test pattern is displayed When Enabled the user stored image is displayed Note the unit is shipped with no user default image stored Position 4 Edge Rate Control This option is used to control the Edge Rate of the output video Since modern electronics are capable of extremely high frequency operation and all of these early mechanical formats were of very low bandwidth this option can better match the output bandwidth to that of the Output Standard When Enabled this option will control the Edge Rate of the Video Output to limit it s bandwidth to that of just higher than the Output Standard When Disabled no limiting is performed on the Video Output and it will contain extremely high frequencies This option should normally be set to Enabled
11. due to the nature of AC synchronous motors If a television that was designed to use 60Hz mains is used on 50Hz mains it will run 20 slower and vice versa The converter will now allow televisions designed for one part of the world to work in another part with different AC mains frequency 2 A Reference Hold option was added to make the output track the last reference input even after it has been removed Revision 3 0 November 7 2009 1 New release based on new 3 x hardware 2 Multi standard capable up to 16 unique formats 3 Reference input added for synchronizing to an external reference signal 4 Improved image scaling algorithms 5 Improved default image 6 Optional internal LED Current Driver board 31 Firmware Revision History Revision 1 0 April 23 2007 1 Initial release Note Hardware Firmware revision level can be found on bottom label of unit 32
12. e algorithms used for conversions e Full three frame memory for stable output regardless of input e Versatile I O Composite Video Input NTSC PAL 1 Vpp 75 ohm Video Output various standards 1 Vpp 75 ohm Reference Input 30V 20K ohm ZeroCrossingDetector Current Driver Output 333ma maximum optional DC power 7 14Vdc 200ma Introduction Front Panel The front panel is shown below Composite Reference Video Input Input Status LED Composite Video Input The Composite video input signal is supplied to this RCA or BNC connector and needs to conform to the NTSC or PAL SECAM video standards The unit automatically detects which type of signal is connected and no user intervention is required For complete information about the characteristics of this input please refer to the Specifications section found later in this manual Status LED The tri color status LED conveys the current operating state of the converter Solid Red No video or reference signal detected Default image displayed Solid Yellow Converter locked to video or reference input Solid Green Converter locked to video and reference input 4 Introduction Slow Flashing Options setting mode Red Option Disabled Green Option Enabled Yellow Option Not Available Pulsating Red Converter in low power Sleep mode Fast Flashing Converter Storing default image to internal FLASH Yellow or Green Alternating Thermal overload on opti
13. en multiplied to increase it to 81MHz plus 4 The additional 4 is used by the internal Digital Phase Locked Loop and will be discussed later Using this clock a video timing generator or flywheel is created in the FPGA to generate all timing signals for the selected output standard All line frame pixel count and line count generation is done in this process This is the main heartbeat process for the entire design Using these timing signals the video data that was stored in the frame memories synchronous to the incoming ITU video clock can now be clocked out With all the above timing now generated the output video can be created The signals from the flywheel are routed to the video output DAC at the appropriate times in the signal while the processed video from the frame memories is routed to 20 Introduction the video DAC during the active portions of the video signal The DAC is run at a three times over sampled rate to reduce filtering requirements and increase SNR The video is then filtered and buffered before being sent to the video output connector During conversion the unit provides two different methods for converting from the input frame rate 25 or 30fps to the output frame rate 12 5 through 25 fps In the first method all three frame buffers are used and images are only read out of a buffer after a new image has been entirely written into the buffer first This provides good image quality with the drawback
14. er supply to the unit The Auxiliary Button must remain depressed until the front panel Status LED starts blinking At this point the pushbutton may be released The Status LED will repeat a pattern of two fast yellow flashes to indicate the unit is in the Setup and Test Mode There are four different behaviors that can be selected You can scroll through these by depressing the auxiliary pushbutton to increment to the next test in a round robin fashion Mode 1 This mode is used to observe and set the black level output of the converter when used with the optional internal Current Driver This adjustment is not necessary when using an external Current Driver When this mode is selected the converter outputs video black To adjust the black point of the Current Driver momentarily short the Test Point TP1 inside the converter must remove case lid with a screw driver or similar tool The Status LED will show two fast red flashes to indicate Black Level Setting Mode This also forces the Black Level Control option to enabled during this test Using the Options and Auxiliary Buttons the level can be adjusted up or down and should be set to where the Current Driver output is just coming on This can easily be determined by viewing a connected LED for when the lamps just turn on Once the desired level is obtained momentarily short TP1 again to save the result in FLASH memory and return to the normal Test Mode To exit this mode without saving the va
15. ertical Frequency Scan Type Video Characteristics A 48 25p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics B 50 25p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 6 5 108 cropped 120 48 15 Hz 720 Hz Mechanical Progressive Left to Right Top to Bottom 38 9 KHz 100 0 video sync ratio 6 5 108 cropped 120 48 20 Hz 960 Hz Mechanical Progressive Left to Right Top to Bottom 51 8 KHz 100 0 video sync ratio 4 3 120 48 25 Hz 1200 Hz Mechanical Progressive Left to Right Top to Bottom 72 0 KHz 100 0 video sync ratio 4 3 120 50 25 Hz 1250 Hz Mechanical Progressive Left to Right Top to Bottom 75 0 KHz 100 0 video sync ratio 28 Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics D 60 20p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics E 60 25p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics Supported Output Standards C 60 12 5p Baird 3 7 120 72 cropped 180 end 6 pixels stretched 12 5 Hz 750 Hz Mechanical Progressive Bottom to Top Right to Left 45 0 KHz 100 0 video sync ratio 6 5
16. for blacks while the contrast control can setup for peak whites this is not required on the optional internal Current Driver as this is handled automatically User options like Gamma and Invert can be adjusted to match what the user supplied lamp driver requires 14 Introduction Typically some means of synchronization is required for the television to avoid having the user constantly adjust the speed and phase of the motor to keep the image centered and phased For the NBTV standard this is done through the insertion of standard type line sync pulses in the video with the pulse missing on line one for frame synchronization A properly equipped NBTV television will lock to the output of the converter with no other adjustments necessary The line and frame phasing should be correct every time the television is operating after initial adjustment For televisions like the Baird which used an AC DC motor and a synchronous phonic coil the video output signal from the converter needs to be filtered and fed through an amplifier to the phonic coils on the television This will lock the television to the converter but the user will still need to phase center the image For televisions that used an AC synchronous motor like the Western Visionette an AC Mains reference must be connected to the Reference Input on the converter so the converter can lock to the same signal as the motor in the television In order to accomplish this a standard 6 12VAC t
17. ge will used When Disabled the negative going edge will be used For most applications this is not important but may be useful to the experimenter Position A Reference Fast Tracking This option is used to control the loop speed of the Reference Digital Phase Locked Loop used to synchronize the Video Output to the Reference Input When Enabled the converter will lock faster and track closer to the Reference Input signal This can be good and bad If the Reference Input contains a lot of jitter or other errors the converter will more likely track those errors in this mode and possibly even make them worse do to overall system damping This may result in an image that hunts along the line direction trying to keep up with the Reference signal It can be useful however for the experimenter using modern electronics in there mechanical television When Disabled the unit will take twice as long to lock but will provide a more damped and more stable lock This option should normally be set to Disabled Position B Reference Hold This option is used to control the behavior of the Reference Digital Phase Locked Loop used to synchronize the Video Output to the Reference Input when no reference is detected When Enabled the Digital Phase Locked Loop will hold the 12 Introduction last valid value until a new reference signal is detected or the output standard is changed When Disabled the Digital Phase Locked Loop will always return to i
18. ical Progressive Left to Right Top to Bottom 22 5 KHz 100 0 video sync ratio 26 Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 5 36 10p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 6 39 12 5p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 7 45 15 3i1 Western Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics Supported Output Standards 4 32 12 5p NBTV 2 3 32 cropped 60 120 12 5 Hz 400 Hz Mechanical Progressive Bottom to Top Right to Left 24 0 KHz 70 30 video sync ratio 1 1 90 cropped 120 36 10 Hz 360 Hz Mechanical Progressive Left to Right Top to Bottom 16 2 KHz 100 0 video sync ratio 4 3 90 39 12 5 Hz 487 5 Hz Mechanical Progressive Left to Right Top to Bottom 21 9 KHz 100 0 video sync ratio 1 1 90 cropped 120 45 15 Hz 675 Hz Mechanical Triple Interlaced Right to Left Top to Bottom 30 3 KHz 100 0 video sync ratio 27 Supported Output Standards 8 48 15p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 9 48 20p Image Aspect Ratios Active Pixels Lines Horizontal V
19. ing sets RCA proposed a method of modulating the color components of the video signal onto a subcarrier in the video For reasons beyond the scope of this manual a frequency needed to be chosen so that no standing patterns in the color signal would result This required lowering the vertical frequency from 30Hz to 29 97Hz While this change caused no adverse side effects on televisions it has created a legacy of problems for modern video equipment Instead of being able to use integer numbers like 24 25 and 30 we now have to include 29 97 which makes many calculations and conversion extremely difficult For digital processing the ratio 1000 1001 has been established as the conversion between 30 and 29 97 video The digital video data is then routed to the FPGA where it is further processed The data is sent to the internal frame memories in round robin fashion The frame memories are large enough to hold three frames of video so there is always enough data to keep an uninterrupted flow to the output The video data is scaled prior to storing in the field memories This scaling is done with a multi tap FIR filter for the horizontal downscaling and averaging for the vertical Extra processing like that to stretch the outer three pixels on each side of a Baird image is also done at this time All processing on the incoming video is done synchronous to the ITU clock For the output clock the 14 318MHz reference is used as a base This frequency is th
20. is what results Again this will only have an effect on fast moving objects The user can select between the two above methods and choose the one that works best for them Keep in mind the the frame rates of mechanical televisions are very low to start with and fast motion will always look choppy now matter how the conversion is done Standards like the 45 15 31 Western will benefit from the one buffer method since it is an interlaced format and will better utilize the finer temporal granularity It was briefly mentioned earlier in this section that the output clock is actually 4 above 81MHz This is done to allow for a 4 lock range for the Reference Input By implementing a sophisticated Digital Phase Locked Loop in the FPGA the output clock can be frequency and phase locked to a reference clock With 12ns step resolution very fine adjustments are made to keep the output locked to the reference This is done for standards that require an external reference like the 45 15 31 Western 22 Introduction Hardware Setup and Test Mode There is a hidden mode of operation that is used during initial setup and test of the converter that may be useful to some users No harm can be done to the unit by simply entering this mode but care should be taken if the following alignment procedure is attempted To enter the Setup and Test Mode remove the power cable from the unit While depressing the Auxiliary Button on the rear panel reconnect the pow
21. lue remove power from the unit Mode 2 In this mode 100 white is output from the converter and can be used to verify the lamp driver is not clipping 23 Introduction Mode 3 In this mode the default image is displayed Mode 4 This mode selects normal operation This can be used to verify adjustments made in the prior modes on actual input video without having to leave the Setup and Test Mode Updating Firmware If it ever becomes necessary to update the firmware in the unit this can be accomplished through the internal programming port The connector is a standard 8 pin double row 2mm connector A custom cable with the appropriate mating connector is used in conjunction with an Asix Presto or similar programmer A full description of the hardware software and procedure to FLASH the unit can be found in the supplemental programming guide for the converter 24 Specifications Video Input Supported Standards Video Quantization Video Input Video Output Video Output Video Quantization Video Levels Video SNR Reference Input Reference Input Specifications NTSC 29 97fps PAL 25fps SECAM 25fps Obit A D 8 bit data Composite 1 Vpp 75 ohm impedance 1Vpp into 75 ohms 10 bit Effective D A 3 56dB typical 3 0V to 30 V 20K ohms impedance 50Hz 60Hz and frame frequency Current Output optional Current Output General Dimensions Weight Power Requirements Hu
22. midity Temperature 333 ma maximum 14V maximum 12V recommended Thermal protection at 65 C hysteresis to 55 C 2 5mm X 5 5mm connector 2 60 X 2 60 X 1 00 66mm X 66mm X 25mm 2 00z 57g 9Vdc typical 7 14Vdc maximum 1 0 watts typical Full Operation 0 75 watt typical Sleep Mode 20 80 non condensing 10C 45C ambient 50F 110F 25 Supported Output Standards Supported Output Standards 0 n D 24 20p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 30 12 5p Baird Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 30 12 5p TeKaDe Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 30 16 6p Image Aspect Ratios Active Pixels Lines Horizontal Vertical Frequency Scan Type Video Characteristics 6 5 80 cropped 90 24 20 Hz 480 Hz Mechanical Progressive Left to Right Top to Bottom 19 2 KHz 100 0 video sync ratio 3 7 120 36 cropped 90 end 3 pixels stretched 12 5 Hz 375 Hz Mechanical Progressive Bottom to Top Right to Left 22 5 KHz 100 0 video sync ratio 4 3 90 30 12 5 Hz 375 Hz Mechanical Progressive Left to Right Top to Bottom 16 9 KHz 100 0 video sync ratio 4 3 90 30 16 6 Hz 500 Hz Mechan
23. ming is generated using this crystal The video is quantized processed for brightness contrast chroma gain and hue among others and output at the ITU rate of 27MHz on an 8 bit time multiplexed bus with alternating luma and chroma samples No other signals are required from this circuit as the ITU specification describes a method for encrypting the horizontal and vertical timing information directly into the digital data using timing reference makers or TRS codes A brief description of the ITU 601 656 specification is as follows Fundamental quantization frequency 13 5MHz Pixel Resolution 720 H x 486 V NTSC 720 H x 576 PAL Image Aspect Ratio 4 3 Pixel Aspect Ratio 1 1 NTSC 0 9 PAL Horizontal Frequency 15 734 Hz NTSC 15 625 Hz PAL Vertical Frequency 29 97 Hz NTSC 25 Hz PAL Clocks per Line 1716 NTSC 1728 PAL 27MHz clock Clocks per Frame 900900 NTSC 1080000 PAL 27 MHz clock Note that the vertical frequency is 29 97Hz for NTSC not 30Hz as expected This is due to the NTSC color system that was first ratified in 1953 19 Introduction All monochrome television transmissions prior to this standard used exactly 30Hz or 30 frames per second so as to be in sync with the AC mains frequency This is done to reduce distortions in the image due to induced AC fields or hum from the power supplies of these early sets In order to devise a compatible color system that would show a monochrome signal on exist
24. of jerky motion of fast moving images This is due to the nature of duplicating or dropping frames on the input to match the output rate Because a different number of frames can be dropped each time the frames in the output video may represent frames that were say 1 or 2 apart in the original video This can be shown graphically Frame i Frame 2 Frame j Input Video 30fps Frane 1 Frame 2 Output Video 20fps The closest frame in this example was the third one meaning the second one was dropped The next time the second one may not get dropped meaning there is a difference in time between two output frames that is not consistent This will only have an effect on fast moving objects Another method is to use just one frame buffer and have the input and output writing and reading to it at the same time This results in smoother output motion since the output image will change immediately when the input image changes The drawbacks to this method are since the output image changes immediately it may be in the middle or anywhere in the image when the change takes place and this position will change over time This can be shown graphically 21 Introduction Frame 2 Frame j Input Video 30fps Frane 1 Frame 2 Output Video 20fps In this example the new image being written into the buffer caught up with the image that was being read out of the buffer in the middle of the image The tearing of the image
25. onal Current Driver output Red and Green Reference Input The Reference Input is required for use with certain standards but is available on all standards There were two main methods of synchronization used in early mechanical television one filtered a portion of the video signal and fed it to phonic coils on the television This method was used when viewing over great distances since the transmitter and receiver where not expected to be on the same AC Mains grid The other method assumed the AC motor at the transmitter and receiver where powered by the same AC Mains grid so were inherently in sync It is for this type of setup the Reference input is mainly used One of three different frequencies can be used with all standards a 50Hz Mains reference a 60Hz Mains reference or a frame reference The frame reference must correspond to the frequency for the selected standard as shown in the Appendix Support Output Standards For instance the 45 15 31 Western standard will only accept a 15 Hz frame reference pulse in addition to the two Mains frequencies The supplied signal to this input must be within 4 of the shown value or the unit will not lock to it The input is an edge sensitive zero crossing detector so the actual shape of the signal is irrelevant as long as the selected edge to edge timing is fairly stable The converter will filter out high band noise but low in band frequencies may cause the converter to hunt with the
26. ond This will place the unit into the Options Setting Mode Next choose the desired option using the Selector Switch The front panel Status LED will blink green if the option is enabled red if it is disabled and yellow if not supported To change the state of the option momentarily depress the Options Button to toggle between enabled and disabled When all desired options are set again depress the Option Button for 1 second to exit the Options Setting Mode Also the unit will automatically return to normal operation if the Selector Switch and Option Button are not changed for 1 minute Note Be sure to return the Selector Switch to the desired Output Standard setting after changing the User Options Position 0 Sleep This option is used to disable the automatic Sleep Mode When Enabled the Sleep Mode will force the unit and it s output into a low power state if no video input is detected for 1 hour When Disabled the unit will never go to sleep Position 1 Gamma This option is used to select the output mode of the converter between gamma corrected and straight video Since modern video is pre corrected at the source to compensate for the gamma of CRT s and since most lamps used for mechanical television are linear Neon LED etc gamma correction needs to be provided to correct the video This feature performs the correction accurately in the converter so it is not required in the lamp driver When Enabled gamma correction will
27. ransformer can be used to feed the Reference input 30V maximum peak If the signal is noisy it may be beneficial to filter the signal with a 4 7K resistor and a 0 1uF capacitor This will filter out much of the high frequency noise For the prior two examples the user will always have to adjust the frame and possibly the line phase every time the television is operated This is the nature of these types of early mechanical television There is normally some means provided on the television to accomplish this phasing Alternatively the user can use the Auxiliary Button on the back of the converter to perform the frame phasing without having to use the television Each time the Auxiliary Button is momentarily depressed the frame will jump down one line Each time the Button is held for 1 2 seconds the frame will jump up one line If your television is a modern experimental unit with a frame sync output pulse this can be used to drive the Reference Input of the converter With this type of system once the phasing is adjusted it should never need to be readjusted and the television should always power up correctly phased Since the converter contains three full frames of video memory the output signal will always be stable regardless of the video input signal Normally a mechanical television would require relocking and rephasing each time the video input signal changed but the converter eliminates this entirely Once the television is locked to
28. serting a small flat blade or phillips screw driver into the hole and engaging the slots in the switch If the Option Button is pressed see below the current Output Standard is frozen and the Selector Switch is used to select the desired user programable option Options Button This pushbutton is used to enter the Options Setting Mode and to change the state of the User Options The button can be depressed by inserting a paper clip or other small tool into the hole in the back of the unit When the Option Button is depressed for 1 second the unit enters the Option Setting Mode and freezes the currently selected Output Standard By using the Selector Switch you can choose the desired option position The front panel Status LED will blink green if the option is enabled red if the option is disabled and yellow if the option is not supported When the desired User Option is chosen using the Selector Switch the Option Button is pressed momentarily to toggle the option between enabled and disabled Each option can be programmed in this manner When finished the Option Button is once again depressed for 1 second to exit the Option Setting Mode Also if no changes of the Selector Switch or Option Button are detected for 1 minute the unit will automatically exit the Options Setting Mode and return to normal operation When the unit returns the normal operation the Selector Switch may need to be returned to the desired Output Standard Current
29. signal must not be disturbed during this process After the image is stored the Status LED will return to solid yellow or green Once an image is stored whenever there is no video input connected to the unit the default image stored in the FLASH may be outputted user option to select between this image and the built in test pattern Caution Because of the nature of the partial field memory contained in this unit the default image is stored in bands of several lines at a time If the connected video is not stationary during the storing process the resulting image will be distorted The best way to provide a stationary image for storing is to use the output from a computer video card ora DVD PVR player in pause A typical VCR without a TBC in pause is not suitable for this use Power The converter requires a power source of between 7 0 and 14 volts DC at 200 mA A 9 volt DC power supply is recommended to reduce power consumption 12 Vdc is recommended when driving a NEL 1M lamp from the optional Current Driver Voltages over 16 volts will damage the unit The unit has a reverse polarity diode in series with the input so it will not be damaged by reversal of polarity The 8 Introduction unit uses a standard 2 1mm X 5 5mm center positive coaxial power connector as found on most consumer electronic equipment User Options As previously outlined using a small tool such as a paper clip carefully press the Options Button for 1 sec
30. t s nominal setting when no reference signal is detected This option should normally be set to Enabled Operating Modes Normal Full Operating Mode no Reference When valid video is present the Status LED will show a solid yellow light and the unit will output converted video on the video output connector This mode is appropriate for standards that didn t originally use a Reference like the 30 12 5p Baird or the 32 12 5p NBTV Normal Full Operating Mode with Reference When valid video and an appropriate Reference signal are present the Status LED will show a solid green light and the unit will output converted video on the video output connector in sync with the Reference input This mode is appropriate for standards that used a Reference like the 45 15_3i Western format These formats typically used a synchronous AC motor to drive the disk so the converter needs to also be synchronized to the same AC mains source For complete information about the characteristics of this input and how to use it in a typical application please refer to the Typical Connections section found later in this manual Default Image Mode When no valid video is connected to the composite input the converter will output a default image This can be used to verify operation of the unit or aid in setup of the television The image can either be a user stored image or the built in test pattern The built in test pattern consists of an 8 step ramp on the
31. t ratio of the incoming video to the output video format This can be easily achieved through standard digital methods utilizing scalers and FIR filters This will be discussed in detail Temporal correction involves changing the frame rate of the incoming video to match the outgoing video It was decided that no off the shelf components existed that would provide the desired functionality so a FieldProgrammableGateArray or FPGA was chosen to provide all the digital functionality By adding input output circuitry and ancillary circuitry to the FPGA the entire system could be realized The basic building blocks to the design are FPGA video decoder ADC and multiple power supplies A brief description of each part follows FPGA Video Decoder Video DAC Xilinx XC3S250E 4VQ100 250K gate equivalent 216Kb block RAM 1 2V Core 2 5V Aux 3 3V I O TI TVPS5150AM1 9bit ADC s 2X Over Sampled Line Locked Clock 4 Line Adaptive Comb Filter Multiplexed 8bit YCrCb output bus Proprietary Design 10bit effective DAC 35 MSPS maximum conversion rate 56 dB SNRs FLASH Memory Winbond W25Q80BV 8Mb Serial FLASH ROM 18 Introduction Topology A simplified block diagram of the circuitry is shown below Video Output Reference amp Input The incoming video is digitized and processed by the TVP5150AM1 using a 14 318MHz reference crystal to the ITU 601 formerly known as CCIR601 specification All internal ti
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