I have a standard NTSC monochrome composite video source that I need to digitize, process (in an FPGA), and then convert back to composite.
Analog devices has some nice parts for the decode side (AtoD) and the encode side (DtoA) and I'll use them if I can't find anything else.
Does anybody have any experience with other manufacturers' video encode/decode parts, and if so, who are those manufacturers?
Thanks much.
Bob
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Why avoid Analog? I have used the ADV7138B and it's very nice.
Go look at schematics for FPGA dev boards with composite video IO. I know I've seen other chipmakers with similar parts.
BTW if it's really just monochrome you might get by with a plain old ADC and DAC (certainly the DAC).
-- Ben Jackson AD7GD http://www.ben.com/
Ben,
I'm not trying to avoid Analog, I'm just curious as to who might have similar parts. I will look at FPGA development boards to see what they use. That's a good idea. Thanks.
If I use a plain old ADC and DAC then the FPGA will have to do much more video processing in that it will need to recover the horizontal and vertical sync. These so-called video decoder chips do the digitizing as well as the sync recovery, so it makes the job much easier.
Bob
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I've used the TI TVP5150 with an FPGA and the AD725 + THS8134 for video output.
Like someone else said, there are many FPGA development boards on the market with composite video in-out capability on board.
Dave.
Do you mean NTSC with no chroma information, but still a color burst, or do you mean RS-170B (NTSC timing, but no color burst)?
Not that it changes things much, unless the lack of color burst confuses the vid capture chip enough to compromise your video.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
I think you can still get sync stripper chips, but I only look over the shoulders of video circuit designers (and occasionally help out with implementing PLLs digitally); I don't actually design video circuits myself.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
The requirement doc stated it was RS-170 but the camera is color. I think the idea is that they intend to put the camera into monochrome mode, so the color burst and associated chroma won't be there. However, I want the design to support both modes. I don't think this will be a problem - at least for the Analog Devices video encoder and decoder chips.
20 years ago, I worked on a project that required me to lowpass the burst out of the signal so that I could sample-and-hold the "back porch". No big deal. The good news is that nowadays it is MUCH easier to deal with these issues (too easy, if you ask me).Bob
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Philips Semiconductors had some good stuff. They are called NXP
-- Paul Hovnanian paul@hovnanian.com ----------------------------------------------------------------------- Have gnu, will travel.
Thanks, Paul.
It looks like they have several parts that will work. Their devices have JTAG interfaces that will allow for more complete boundary scan testing in conjunction with our FPGA. The Analog Devices parts don't offer this capability.
Bob
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They actually do various amounts of the job. Read the datasheets carefully. Also sync separators / regenerators are not that hard (a tube or two).
That task would overwhelm most recent graduates.
Nor would i have used a lowpass technique, gated sampling was already well established technique, i would only have to adjust the delay.
I agree. Fortunately, electronics was my hobby before I entered college. Most people in my graduating class had NO idea what they had just learned.
The sampling was gated (as is always the case in a sample and hold). The problem is that with my home-brew sampler, the output impedance of the capacitor-driving-amplifier required a fairly large window in order to get an accurate measurement. The video signal's "back porch" was just too short to do anything but completely kill the colorburst.
Bob
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