[FFmpeg-user] Setting Display Aspect Ratio of MXF/DV video

Marc Tarin ch0d4 at free.fr
Tue Apr 14 10:25:10 CEST 2015

> For future questions, please always test current 
> FFmpeg git head.
> (Nothing else is supported here.)

Sorry, I obviously forgot to mention that I had re-run the tests with
the 20150413 static build (based on git g013498b) which was the
latest available at the time I wrote my message.

>>     Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 16:15 DAR 4:3]

>> A bit of context: the input file is supposed to 
>> be broadcasted in 16:9, but as you can see it 
>> is reported as 4:3 by ffprobe.

>I am not sure I understand:
>Do you mean that FFmpeg detects the aspect ratio 
>incorrectly? If yes, this should be fixed first 
>(and all remaining issues depend on this).

FFmpeg is not at fault: the original file was erroneously generated
in 4:3 by the content provider while it should have been created in
16:9. I was just explaining why I needed to fix the aspect ratio.

>> $> ffmpeg -i in.mxf -vcodec copy -aspect "16:9" -an out_copy.mxf

> This does not work because libavformat writes 
> mxf aspect ratio differently from all other 
> containers (sadly).
> To some degree this is related to the fact 
> that mxf aspect ratio is defined in a rather 
> brain-dead way.

Ok, thanks for the info.

>> At this point, my understanding is that 
>> the MXF container is always assigned a 
>> display aspect ratio of 4:3, even when it 
>> should be assigned 16:9.

>This is certainly not true but as said, mxf 
>aspect in FFmpeg on muxing is different 
>from other containers.
>(And this is a bug imo.)

This was just a straightforward conclusion of mine, since I couldn't
get it to work as it did with other containers. You made it clear
that it actually works differently.

I guess for now for I'll just stick with FFmbc for this peculiar

Thanks for your answer.



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