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SVGA to composite video

Discussion in 'Electronic Design' started by Another Nick, Dec 3, 2007.

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  1. Another Nick

    Another Nick Guest


    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)

  2. Guest

    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
    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:
  3. This is not a trivial problem

    I would use something like this

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