[FFmpeg-user] Aspect ratio preservation in WMV

[Rodney Baker]

On Mon, 26 Sep 2011 02:18:34 Paul-Antoine Arras wrote:
> Le 24/09/2011 04:17, Rodney Baker a écrit :
> > On Sat, 24 Sep 2011 04:50:52 Paul-Antoine Arras wrote:
> >> Hello,
> >> 
> >> I'm trying to convert the sound of a video from WMA to MP3. To do so, I
> >> 
> >> use the following command line:
> >>      ffmpeg -i input.wmv -acodec libmp3lame -aq 4 -vcodec copy
> >>      output.wmv
> >> 
> >> The sound is converted correctly but the aspect ratio (AR) becomes 4:3
> >> 
> >> instead of 16:9. Then I've tried to force the AR with:
> >>      -aspect 16:9
> >> 
> >> without success.
> >> 
> >> Why does ffmpeg modify the AR while all it has to do in this case is a
> >> simple copy of the video part? How to make it preserve the original AR
> >> (16:9)?
> >> 
> >> Thanks in advance for your help.
> > 
> > You need to provide the full output from ffmpeg.
> 
> Here is the full output from ffmpeg:
> 
> FFmpeg version 0.6.2-4:0.6.2-1ubuntu1.1, Copyright (c) 2000-2010 the
> Libav developers
[...]
> Output #0, asf, to 'output.wmv':
>    Metadata:
>      WM/EncodingSettings: Lavf52.64.2
>      Stream #0.0: Video: WMV3 / 0x33564D57, yuv420p, 720x576 [PAR 64:45
> DAR 16:9], q=2-31, 1k tbn, 1k tbc
^^^^^^^^^^^^

ffmpeg is writing the stream out with an aspect ratio of 16:9 (Display Aspect 
Ratio) and pixel aspect ratio of 64:45 which, with a standard definition 
720x576 picture will be correct for a 16:9 display. What are you using to view 
the resultant output file? Is it showing the correct aspect ratio?  Can you 
force it? 


-- 
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Rodney Baker VK5ZTV
rodney.baker at iinet.net.au
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