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I have been working on a project for some time that involves using frame grabbers to get frames of video from a camera running algorithms on the result.
There are lots of different frame grabbers that work on both analog video (like an RCA or BNC connector carrying an NTSC or PAL signal) and digital video. These frame grabbers typically have 2, 4, 8 or 16 inputs. However, modern computers have generally moved to digital outputs like DVI or HDMI for output while the video is often still in analog.
I want to move everything to digital but until then I have to input analog NTSC/PAL and output the exact same format but cleaned up from the algorithms.

My issue is that while there is a whole standard way to input analog, the output of analog is hiding. We have "frame grabbers" that can take in analog signals to the pc but there are very few options I see to output (playback) the analog signal in the same format.
The onboard and discreet graphics cards no longer have analog. There is no family of "frame putters" that output the NTSC/PAL signals. It seems like there should be a whole family of peripherals for PCI/PCIe that would output analog signals like a screen or with special coding but they do not seem to exist.

What is the best way to output 1, 2, 3 or 4 channels of Analog Video (NTSC/PAL) from an x86 Windows PC?

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1-4 channels simultaneously? Using which connection? Which source material? – slhck Jul 24 '11 at 20:43
@slhck 1-4 channels simultaneously. Preferably as a monitor, but perhaps using an API that is fed frames of the correct size. – Steve Jul 24 '11 at 21:02
All showing same output? Desired framerate? Static images or motion? Distance to display devices? – Linker3000 Jul 24 '11 at 21:21
@Linker3000 All showing different outputs from live video feeds. The distance is short---say, from underneath the desk to displays on the top of the desk. – Steve Jul 25 '11 at 2:25

Unterminated passthrough: If an analog video connection point can be unterminated, you can literally Y adapt or loop the signal to a second device, and the end device is then terminated. Much of the pro analog equiptment has this capability. Pro monitors $$$ will have the same ability, so you can see, and still use the signal.

Distribution amps: will properly split an analog signal into multiples. giving you that analog signal in 2+ places.

IF you could see all the inputs your using, would you still need output out of the computer?

Computer analog output: TVcards, and Media capture cards, both consumer and pro are still available that will output analog out of the computer for media. Some older ATI cards even would output analog signal of the desktop in standard defintion video, like for an analog tv.
In ATI the "all in wonder" was a tv video capture card and a video grafics card combo, and output analog computer, for PCI and AGP ports. ATI-AIW were I think all Digital out for PCI-E

Vga to analog video can be done with Scan Converters which combine and interpolate the 3 VGA analog video signals to video out.

In Digital to Analog conversion there are many boxes ranging from cheap and very fuzzy output , to ~$500 type boxes with as clean a signal as you can get to the SD resolution. simply called DVI to Video , and HDMI to video, or breakout boxes. many companies make them. This link would be a good place to at least search for them

Because digital is taking over and analog is being literally discarded, instead of seeing the lack of analog, see the huge quantity of used analog available for neer free :-) Analog is so phased out that selling many things on e-bay is not worth listing and shipping, so it doesnt get high visability. Send a truck over here, I could fill it for about $500. Old ATI cards could be purchaced for ~$5 that would put out one desktop analog.

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