[FFmpeg-user] Aspect ratio preservation in WMV

[Andrew Wason]

On Sun, Sep 25, 2011 at 7:23 PM, Rodney Baker <rodney.baker at iinet.net.au> wrote:
> On Mon, 26 Sep 2011 02:18:34 Paul-Antoine Arras wrote:
>> 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)


ASF supports a couple of different mechanisms for storing aspect ratio
information, looking in ffmpeg libavformat/asfenc.c it doesn't seem to
use any of them. So I think this is a missing feature.

I think in asfenc.c:asf_write_header1() you would need to write
AspectRatioX and AspectRatioY into the ff_asf_extended_content_header
section.  See the spec:
http://msdn.microsoft.com/en-us/library/bb643323.aspx

Andrew