As it was discussed today on #ffmpeg and #ffmpeg-devel, only IDR frames are considered safe seek points by design of H.264. H.264 has two kinds of pictures which are mapped to AV_PICTURE_TYPE_I: NAL_IDR_SLICE and some other NAL_SLICE. H.264 referencing is arbitrary and GOP concept is not strict, as jkqxz and Mavrik have explained. I my usecase, I need to be sure about slicing the file and not breaking any references. So some introspection of references would be nice, but for now just a programmatic test, or at last a warning from inside libavcodec's H.264 parser, about cross-GOP refs is fine, because in practice, per-GOP handling seems to be fine so far. This is not available at ffmpeg API level. The form of this work is a patch for upstream FFmpeg (upstreamable or not), or separate tool (but additional dependencies or high time/CPU overhead to run it are strongly undesired).
Also, I am interested in any knowledge about applications which generate such files (with cross-GOP refs) in practice, because this request is about working around such case. Sharing sample media files is also appreciated. I am happy to fund this work. Feel free to reply on-list or off-list as you prefer. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
