[FFmpeg-devel] [WIP] Seek / subfile support in concat demuxer

[Nicolas George]

This patch series is work in progress to implement the "seek" option in the
concat demuxer, that allows extracting a part of the file, with exact
accuracy.

It could serve as a base to implement EDL support for formats that require
then.

For video, it defines a new packet flag that informs libavcodec to decode
the frame (it may serve as reference frame for a frame we want) but not
return it to the user.

For audio, it uses the SKIP_SAMPLES side data.

Using side data for video too instead of a flag would also be an option, I
have no strong opinion about it.

For now, it works with threads disabled, but I get some strange
thread-related decoding errors, see trac ticket #3406.

[PATCH 1/6] lavc/pthread: copy packet side data.
[PATCH 2/6] lavu: add pkt_flags field to AVFrame.
[PATCH 3/6] lavc: add AV_PKT_FLAG_DISCARD.
[PATCH 4/6] lavu/frame: add AV_FRAME_DATA_SKIP_SAMPLES.
[PATCH 5/6] lavc/utils: bind SKIP_SAMPLES to the frame.
[PATCH 6/6] concat: support seeking inside sub-files [WIP].