[mythtv-users] MPEG-4 codec and interlaced video: Cr/Cb not encoded properly?

[Scott Alfter]

I figured I'd try encoding some video captured by MythTV to DVD, and I think
I've run across a problem in the way the color information is encoded by the
MPEG-4 encoder.  It doesn't show up in the NuppelVideo compressor, but in
the MPEG-4 compressor, the Cr & Cb components of the bottom field don't line
up with the Y component if there's any substantial amount of motion between
the fields.  They line up pretty nicely with the top field, though, which
would indicate that the compressor is trying to treat interlaced video in
the same manner as non-interlaced video.  It appears to subsample Cb & Cr by
reading every other scanline, which effectively tosses out the bottom-field
color information.  Is this a shortcoming of the MPEG-4 compressor, or is
MythTV not initializing it or sending data to it properly?

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