[FFmpeg-user] Aspect ratio preservation in WMV

[Paul-Antoine Arras]

Le 26/09/2011 01:23, Rodney Baker a écrit :
> 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?
---
When I open output.wmv with VLC, the video is displayed as 4:3, then I 
can force it to 16:9 by software. But the purpose of what I'm trying to 
do is making the video readable on my set-top box, which renders it as 
4:3 (just like VLC) and can't be forced to another ratio.
-- 
Paul-Antoine ARRAS