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352x480 capture -> 352x240 TV viewing; how?

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  • 352x480 capture -> 352x240 TV viewing; how?

    Matrox Marvel G200
    Giga-Byte GA6-BXE
    PII-400; 128M RAM; mucho disk space
    Windows 98 for capture
    NTSC video (USA)

    My ultimate goal is capturing to AVI then encoding to
    MPEG-1 for NTSC VCD playable in tabletop DVD players.
    I capture at 352x480 to MJPEG with minimum compression,
    then encode to MPEG with various encoders (Xing,
    Panasonic, Ligos).

    One of the messages here or in the Matrox docs said
    that it is best to capture at 352x480 if MPEG-1 output
    is the goal.

    Question is about this 352x480 capture, and how it
    gets squooshed to 352x240 for TV viewing. What phase
    of the encoding is supposed to do this, is this what
    is meant by "deinterlacing"?

    This seems to happen by magic in Xing and Panasonic
    encoders, but not in Ligos. I choose "Deinterlace"
    in Ligos' Advanced options, and the video looks OK
    while it is encoding, but when I view the result in
    Media Player, it's double height. Xing and Panasonic
    seem to take care of this. I'd like to use Ligos
    if possible because it gives the option of "one
    header per GOP" which is supposed to make a VCD
    play better in a tabletop DVD player, enabling
    FF and rewind.

    I've also seen inconsistent behavior when viewing
    the MJPEG .avi as it comes out of PC-VCR. Sometimes
    Media Player will show this double height as well.

    Someone who knows about this, please 'splain me!

    Thanks.


  • #2
    Yeah, that's pretty much what "deinterlacing" is. Every other line of your 480-line capture is part of a different picture. If you scale that down to 240 lines, and if your software does some nice interpolation, the lines will mix to make a smooth picture.

    The problem with your other codec is probably that you're not telling it that 240 lines is your goal. You're telling it to mix what's there, but keep the same size picture. Find the place to tell Ligos the picture should be 352x240 when you're done, and everything should work fine.

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