[Ffmpeg-devel] DAR and SAR FFmpeg option confusion

[Robert Swain]

Roman Shaposhnik wrote:
> On Tue, 2007-03-13 at 01:01 +0100, Michael Niedermayer wrote:
>> -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.

SAR = 10/11

DAR = SAR * WIDTH/HEIGHT = (10/11) * (704/480) = 4/3

So there's nothing wrong there if it's cropped. If it isn't cropped then:

DAR = (10/11) * (720/480) = 15/11

Have fun,
Rob