[theora] Further bug discovered with the Directshow decoder

Cristian Adam cristian.adam at gmail.com
Tue Jun 16 17:04:51 PDT 2009

Ivo Emanuel Gonçalves wrote:
> On 6/16/09, Yamuna Jivana dasa <ykhandoo at webmail.co.za> wrote:
>> Also still not sure why videos from my digital camera whose audio is 11025
>> sampling speed,, outputs to a distorted scrambled sound result in the ogv
>> output.  Video is just fine.
> Hi,
> If your disability does not impair you from using the mediafire.com
> web site, could you upload there an original sample from your digital
> camera.  I would like to check for the audio problem.  Hopefully
> someone else will be able to find out what is wrong in the Directshow
> filters.
> -Ivo


The digital camera has mono, 8bit, 11025 sampling speed and 
ffmpeg2theora 0.24 has a bug regarding 8bit mono audio data.

I have taken the audio part from the lion.avi and saved as a wav file.
Compressing the wav file with ffmpeg2theora resulted (screen dump):

$ ffmpeg2theora-0.24.exe test.wav
Input #0, wav, from 'test.wav':
   Duration: 00:00:21.00, bitrate: 88 kb/s
     Stream #0.0: Audio: pcm_u8, 11024 Hz, mono, s16, 88 kb/s
       0:00:10.50 audio: 30kbps video: 0kbps, time elapsed: 00:00:00

the resulted file was around 40kbytes in size. Because ffmpeg2theora
thinks it has 16bit samples the encoded audio file is two times faster.

Using OggEnc v2.85 (libvorbis 1.2.0 [SVN - 20080316]) I have created an 
ogg file which was around 80kbytes and played fine with Windows Media 
Player and VLC.

I don't know a simple workaround for this problem.

I have uploaded both lion.avi and lion.ogv in a zip file here:


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