[FFmpeg-devel] [PATCH] lavf/matroska: Export codecdelay and seekpreroll as metadata tags

Vignesh Venkatasubramanian vigneshv at google.com
Wed Sep 18 00:04:05 CEST 2013

On Tue, Sep 17, 2013 at 2:46 PM, Nicolas George <george at nsup.org> wrote:
>> Codec delay it the number of samples (represented in matroska as
>> nanoseconds) that the decoder has to discard from the beginning of the file
>> before the decoded data is considered valid. So, the demuxer cannot take
>> care of it internally.
> Is it not exactly what the AV_PKT_DATA_SKIP_SAMPLES side data is for?

That is a packet specific field. This information applies to the file
as a whole.
Even though the discard happens only from the first frame, there are other
operations that apply to the file as a whole (like offsetting timestamps). So
it is useful to have this exported as a metadata tag.

Also, as of now ffmpeg's decoder implements support for codec delay for
opus in matroska by looking into the codec's private data and not by looking
at this container element value. So when that support is added, the
implementation will probably use AV_PKT_DATA_SKIP_SAMPLES side data.

> Regards,
> --
>   Nicolas George
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel

More information about the ffmpeg-devel mailing list