[FFmpeg-devel] rtpdec_h264.c RTP to annex-b patch

Martin Storsjö martin at martin.st
Wed Feb 1 20:45:45 CET 2012

On Wed, 1 Feb 2012, Michael Niedermayer wrote:

>> The h264_mp4toannexb bsf isn't exactly what's needed in this case -
>> the data is in annex b format already, but with SPS/PPS as extradata
>> instead of inline in the stream. (This is exactly the same format as
>> libx264 outputs if encoding for mp4 files, when the global header
>> flag is set, FWIW.) Not sure if there currently is any bitstream
>> filter to do exactly this conversion (removing extradata and
>> embedding it into the stream) though.
> dump_extra maybe
> but in how far that would produce valid annex b iam not sure.
> Our decoder will handle it of course but that doesnt mean its compliant
> to the spec.

Hmm, that might actually work.

> [...]
>> Currently, the rtp depacketizer sets timestamps for all packets, but
>> it seems that the h264 parser clears this from the first frame, so
>> that it has dts=pts=N/A.
> that sounds like a bug
>> With the current code, this frame has
>> keyframe=1 set, and the mkv muxer will fail to write it with "Can't
>> write packet with unknown timestamp". With your patch applied, this
>> frame is marked as keyframe=0 by the parser, and ffmpeg.c won't
> Is it or is it not a keyframe ?
> either way this too sounds like theres a bug somewhere

I do think it's a keyframe.

The stream is available publicly in the url as in the previous mail 
(rtsp://albin.abo.fi:8554/sample_h264_100kbit.mp4), if you want to have a 

// Martin

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