[Libav-user] SEI picture timing message and timestamp in decoded frame, h264 es

Michal Rybinski michal.rybinski+ffmpeg at gmail.com
Wed Feb 13 17:15:30 EET 2019

Hi there,

I'm a bit newbie to ffmpeg API and still didn't get a grasp where to look
in ffmpeg code for some answers. I hope for some guideline/explanation. If
this is more suitable for ffmpeg-user mailing list, just let me know.

Playing back a video (using ffmpeg API of course), a h264 elementary
stream. It is possible, that every frame gets additional SEI picture timing
message in that stream. FFMPEG is compiled without "--enable-gpl" and
without "--enable-nonfree" flags (so it's not using x264 in my case).
Reading frames and controlling their displaying using AVFrame
best_effort_timestamp value.

Is FFMPEG taking into account SEI picture timing message contents when
establishing timestamp (pts or best effort timestamp) when my app reads
decoded AVFrame (basically looking into pts and best_effort_timestamp
fields)? If yes - is clockTimestamp calculated from SEI picture timing
overruling/overwriting any other values or is it more complicated? Where
should I look to understand how SEI picture timing message influences
timestamp (and which one in terms of AVFrame fields) when h264/es frame
gets decoded via ffmpeg?

Best Regards
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