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

Carl Eugen Hoyos cehoyos at ag.or.at
Tue Apr 14 01:13:27 CEST 2015

Marc Tarin <ch0d4 <at> free.fr> writes:

> The tests described below where run with an up 
> to date FFmpeg release from the debian 
> multimedia repository:

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


>     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 -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.


> 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.)

Carl Eugen

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