SVGA to composite video


I have an application where I need to replace a CCTV image on a monitor with a 800x600 computer-generated image at certain times. The CCTV images are usually composite (PAL) video. The easiest way as I see it is to convert the SVGA RGB to PAL using an AD725 or something like that and switch between the two PAL sources.

Most of the screens in use (15" TFT) will take either VGA or composite video either by a separate interface option or a menu, so should handle the non-interlaced video at the higher refresh rates and higher lines-per-field than standard TV systems.

My feeling is this should work, but is there any complication I might've overlooked? Is there a better NG to ask this question?

(This is an embedded PC/104 system, so I don't have the luxury of buying a PC/TV card etc)

Thanks Nick

Reply to
Another Nick
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That chip won't help you.

That's not a given, but a good bet.

Yes, you overlooked the fact that "RGB" just refers to how colors are encoded, not to any particular overall video standard. That chip is just a modulator, it will take 15KHz RGB data and create a modulated video signal. It won't convert frame rates or re-size pixels. If you feed it 800 x 600 non-interlaced RGB, it will try to modulate that color information into a 800 x 600 non-interlaced "PAL" or "NTSC" signal which no TV will understand.

Check your local computer store, there are VGA to NTSC boxes, maybe some will work at 800x600. If my 10 year old Voodoo 3 3000 has a chip that lets me see "800x600" on my NTSC TV, surely it exists.

If you have your heart set on on a project, look into these guys:

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Reply to

This is not a trivial problem

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I would use something like this

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Reply to
Martin Griffith

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