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Homebrew YPrPb/NTSC transcoder sync questions?

Discussion in 'Electronic Repair' started by [email protected], Dec 17, 2003.

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  1. Guest

    Hello all... not sure if this is on-topic, but I figured someone might
    know something about it.

    My new roomate has an HDTV-ready set with component in, and I like the
    idea of using a real, honest-to-goodness modeline out of the VGA port to drive
    the TV. I've been scouring the 'net for some good plans to build a transcoder
    (VGA->Component video), but figured I'd ask here too, in case anyone knows.

    I'm looking to build a "Swiss army knife" transcoder. Takes VGA in,
    loops VGA back out, and provides component out (YPbPr), but also provides
    composite and S-Video out. The second circuit (composite/svideo) is easy, since
    it's all done in the AD724 chip. The first I've got issues with:

    Does anyone know why all the plans for transcoders on the 'net have H/V
    sync generators (one-shot timers, delayed logic gates, etc)? Why can't it just
    use the sync pulse from a custom modeline off the VGA port? Also, does anyone
    know where to find the specs for sync pulse length for HDTV modelines?

    Thanks for any advice:

    * The prime directive of Linux: *
    * - learn what you don't know, *
    * - teach what you do. *
    * (Just my 20 USm$) *
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