[Libav-user] Something specific with Theora and 'black empty frames' ?

[Soltic Lucas]

Le 5 juin 2011 à 19:22, John Stebbins a écrit :

> On 06/05/2011 04:49 AM, Soltic Lucas wrote:
>> Hello,
>> 
>> I'm currently working on a C++ movie playback library relying on FFmpeg and I recently noticed audio would get desynchronized with video when reading OGV files, whereas it's working fine with H.264/AAC.
>> 
>> What I actually noticed is that the black frames at the beginning of the movie are skipped when using the OGV decoder. Whereas they're not with the H.264/AAC decoder. I also noticed that 3 frames at the beginning of the movies don't get decoded (return code -1). This is probably where the "few seconds of black images" disappear (actually there's exactly 3s of black images). But error code -1 is not really meaningful and I don't know how to handle these few frames. After these 3 frames everything is decoded properly.
>> 
>> Here's the output when reading the OGV file:
>> [ogg @ 0x11eb600]max_analyze_duration reached
>> Input #0, ogg, from '/Hors sauvegarde/sintel-1024-stereo.ogv':
>>   Duration: 00:14:48.04, start: 0.000000, bitrate: 2692 kb/s
>>     Stream #0.0: Data: skeleton
>>     Stream #0.1: Video: theora, yuv420p, 1024x436, 24 fps, 24 tbr, 24 tbn, 24 tbc
>>     Stream #0.2: Audio: vorbis, 48000 Hz, stereo, s16, 448 kb/s
>>     Metadata:
>>       ENCODER         : Lavf52.78.5
>>     Stream #0.3: Invalid Codec type -1
>>     Stream #0.4: Invalid Codec type -1
>>     Stream #0.5: Invalid Codec type -1
>>     Stream #0.6: Invalid Codec type -1
>>     Stream #0.7: Invalid Codec type -1
>>     Stream #0.8: Invalid Codec type -1
>> [theora @ 0x120c600]Header packet passed to frame decoder, skipping
>> (then the 3 decoding errors with code -1 when using avcodec_decode_video2())
>> 
>> If that can be of any help, the file was downloaded from : http://www.sintel.org/wp-content/content/download.html (OGV Stereo)
>> 
>> 
> This is probably this problem https://roundup.libav.org/issue2669

Indeed it does look like to be the same issue, but there doesn't seem to be any reaction from the development team for now.
As for my issue, I realised that the 3 errors do not occur at the beginning of the movie. Thus the empty frames look to be ignored silently.

Anyway thanks for your report.

Lucas Soltic