[Libav-user] Criteria for h.264 key-frame detection

Paul B Mahol onemda at gmail.com
Fri Oct 25 17:59:34 CEST 2013

On 10/20/13, Robert Krueger <krueger at lesspain.de> wrote:
> Hi,
> I have AVCHD files from a camera (Panasonic Lumix GH1) that demux and
> decode with libavformat/libavcodec detecting no other keyframe but the
> first (both, the first video packet and video frame are marked as
> keyframe), which is not what I would have expected for those clips as
> the GOP structure of files produced by this camera is known to be
> different.
> My question is now, what libavcodec/libavformat uses as criteria to
> decide whether a packet is a keyframe packet or a frame is a keyframe
> in this case. Does it only trigger in the case of IDRs or are recovery
> point SEIs also detected? Should I open a trac issue for this with a
> sample?

AFAIK h264 key frame detection is in parser. And only in two places in
code is key_frame set to 1.

If key frame detection is wrong for certain file that it could be bug.
Without sample it is impossible to find out.

I would recommend to open trac issue.

> My requirement is, I want to find points in the stream suitable for
> random access using libavformat/libavcodec. What are my options for
> this kind of files?
> Thanks,
> Robert
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