[FFmpeg-devel] [PATCH 6/7] mxfdec: set sample aspect ratio for uncomp rec601

Philip de Nier philipn at rd.bbc.co.uk
Wed Feb 29 13:56:30 CET 2012


On 28/02/12 18:36, Baptiste Coudurier wrote:
> On 02/28/2012 06:16 AM, Philip de Nier wrote:
>> ---
> This one I'm hesitating. The problem is that setting sample aspect ratio
> to these values will break
> the rule width/height == dar/par which is expected in many places.
> I believe sample aspect ratio should follow the rule and another field
> like clean aperture should be exported.
> Furthermore, this assume the source is analog and not digital.
> Michael ?

Thanks for reviewing and applying the patches.

My 2 cents on sample aspect ratio:

I guess that is MPEG's rule on SAR, DAR and picture dimensions and if 
FFmpeg is following that then sample_aspect_ratio is different from the 
one I was assuming.

A practical issue is that if I run "ffmpeg -i unc_625_16x9.mxf test.mov" 
and the mxf demuxer does not set the sample_aspect_ratio to 118/81, then 
the quicktime file has the incorrect (i.e. not h_spacing=118, 
v_spacing=81) pixel aspect ratio in the pasp tag.

Not sure I understand the comment about analog versus digital as Rec. 
601 deals with digital television


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