[MPlayer-dev-eng] enhancement for yuv4mpeg output driver

D Richard Felker III dalias at aerifal.cx
Wed Jan 19 22:58:17 CET 2005

On Wed, Jan 19, 2005 at 01:31:26PM -0800, Trent Piepho wrote:
> > > mplayer has the wrong idea of the pixel aspect isself, for example, a 720x480
> > > 4:3 NTSC DVD should be scaled to 720x528, not 720x540.  So I added an 'aspect'
> > 
> > 	The scaled size isn't placed in the yuv4mpeg2 header so I think that's
> > 	a different issue (when playing the movie on the computer for example)
> > 	but you're right, the wrong thing is being done.
> > 
> > 	The SAR (sample aspect ratio) placed in the yuv4mpeg2 header 
> > 	should be 10:11 for "NTSC", and 59:54 for "PAL" (or 40:33 and 118:81
> > 	for 16:9 movies in the two video systems).  Hmmm, but when you're
> > 	decoding a SVCD the SAR is 15:11 and 59:36 respectively).  Does the
> > 	yuv4mpeg module have sufficient knowledge to emit the correct 'A'
> > 	tag?  If not then "0:0" is appropriate.
> I use mplayer's idea of the correct scaled size of the video to guess the
> sample aspect ratio.  In some cases this works, a 704x480 4:3 DVD will have
> a SAR of 10:11, a HDTV capture will have a SAR of 1:1, etc.  In some cases
> it is sligtly off, due to pixel rounding.  In others it is off by a bit more,
> because mplayer has the wrong idea of the SAR itself.

yes, using picture aspect ratio instead of sample aspect ratio is very
very stupid... if/when mplayer is completely overhauled/replaced, it
will use sample aspect instead.


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