[opendtv] Re: [MPEG] Re: Growing uncomfortable with Samsung
- From: Ron Economos <k6mpg@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 23 Jan 2005 19:46:19 -0800
The prime example of this is 1920x1080i. 1080 is not divisible by 32
(32 for interlace, 16 for progressive) so the macroblock height is 68,
or 1088 lines. On the LSI Logic 3-chip HD MPEG-2 encoder, we
ended up changing the pixel padding from gray (Y=128,Cb=128,
Cr=128) to black (Y=16,Cb=128,Cr=128) because many (but
not all) PC based decoders ignore the 1080 vertical_size in the
sequence header and display the entire 1088 line raster.
Ron
Craig Birkmaier wrote:
>There are a few "unwritten" constraints on MPEG-2 because of the
>macroblock structure. It just makes sense to pick line lengths that
>are multiples of macroblocks. But this does not prevent you from
>using ANY raster size -- you simply pick the next largest block
>increment and pad out any samples in the blocks that are not used.
>Remember, the source must first be resampled before it is compressed,
>when you use sub line lengths - reversing this is trivial.
>
>
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