[Ffmpeg-devel] DAR and SAR FFmpeg option confusion
Roman Shaposhnik
rvs
Tue Mar 13 03:06:22 CET 2007
Hi
On Tue, 2007-03-13 at 01:01 +0100, Michael Niedermayer wrote:
> > > I haven't done any print debugging but looking at the SAR reported by x264,
> > > these values are not affected by -vaspect, grepping for vaspect in the code
> > > returns no results and it isn't documented anywhere yet ffmpeg doesn't report
> > > any unrecognised option error. :/
> >
> > I have the same issue with DV (not being able to use SAR for real) so
> > if you ever figure this out -- there'll be at least two clients for the
> > functionality.
>
> -aspect should set DAR, DAR + width and height -> SAR if this doesnt work
> its a bug
Well, here's the problem DV has (and please let me know if I'm missing
something or if the solution is obvious). Lets take NTSC 4:3 DV as an
example here (just to talk in numbers as opposed to variables):
1. FRAME WIDTH == [width in the quote above] == 720
DISPLAY FRAME HEIGTH == FRAME HEIGHT ==
[height in the quote above] == 480
2. DISPLAY FRAME WIDTH == 704
3. DAR == 4:3
Now, given your formula, the SAR will be calculated as being 8:9
where the correct one is 10:11.
As usual, http://www.mir.com/DMG/aspect.html provides more details.
Thanks,
Roman.
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