[Libav-user] Libavformat - Guranteed seeking before keyframe

[ilkercan Kaya]

Hello Everyone,

I am trying to seek my audio ogg file with the following:

int64_t targetPts = av_rescale_q(seekTimeMicro, AV_TIME_BASE_Q, streamTimeBase);

av_seek_frame(avFormatContext, streamInfoIndex, targetPts,
AVSEEK_FLAG_BACKWARD);


This works all fine. Most of the time AVSEEK_FLAG_BACKWARD makes sure that
the stream is seeked to a time before targetPts. However, there are times
the opposite happens, seeking a time after targetPts. I can see this with
the first frame I request from avcodec_receive_frame() having pts
(avFrame->pts) greater than my targetPts. I need to ensure that the first
frame I receive is always smaller than my targetPts. (it's an overhead in
my system, long story).

I read it that here
<https://stackoverflow.com/questions/20734814/ffmpeg-av-seek-frame-with-avseek-flag-any-causes-grey-screen>:
"It appears that, for some reason, av_seek_frame() using
AVSEEK_FLAG_BACKWARD returns the next keyframe when the frame that I am
seeking is the one directly before this keyframe. Otherwise it returns the
previous keyframe (which is what I want).". I suspect that this is the
case. However, this post is too old so it might be outdated.

Could you help me?
Thank you!
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