Problem with ffmpeg function avformat_seek_file()

Question

I am trying to seek the given frame in the video using ffmpeg library. I knew that there is av_seek_frame() function but it was recommended to use avformat_seek_file()instead. Something similar mentioned here.

I know that avformat_seek_file() can't always take you to exact frame you want, but this is ok for me. I just want to jump to the nearest keyframe. So i open the video, find videostream and calling it like this:

avformat_seek_file( formatContext, streamId, 0, frameNumber, frameNumber, AVSEEK_FLAG_FRAME )

It always returns 0, so i understand it as correct finish. However, it doesn't work as it should to. I check byte position like here before and after calling avformat_seek_file(). Actually it changes, but it changes always in the same way whenever i'm trying to put different target frame numbers! I mean that byteposition after this call is always same even with different frameNumber values. Obviously, i'm doing something wrong but i don't know what exactly. I don't know if it does matter but i'm using .h264 files for that. I tried different flags, different files, using timestamps instead of frames, flushing buffers before and after and so on but it doesn't work for me. I will be very grateful if someone could show me what is wrong with it.

score 5 · Answer 1 · edited Mar 14 '20 at 17:41

I had the same issue, see the code bellow (it works for me):

    ...
    checkPosition(input_files[file_index].ctx);
    ...

    void checkPosition(AVFormatContext *is) {
        int stream_index = av_find_default_stream_index(is);
        //Convert ts to frame
        tm = av_rescale(tm, is->streams[stream_index]->time_base.den, is->streams[stream_index]->time_base.num);
        tm /= 1000;

        //SEEK
        if (avformat_seek_file(is, stream_index, INT64_MIN, tm, INT64_MAX, 0) < 0) {
            av_log(NULL, AV_LOG_ERROR, "ERROR av_seek_frame: %u\n", tm);
        } else {
            av_log(NULL, AV_LOG_ERROR, "SUCCEEDED av_seek_frame: %u newPos:%d\n", tm, is->pb->pos);
            avcodec_flush_buffers(is->streams[stream_index]->codec);
        }
    }

Hi, This is working for ffmpeg 0.11.1 and below versions. But, when I use above versions(ffmpeg 2.1 and above) I am getting problem means when we apply seek, some of mp3 songs are playing above duration also. Will u tell any solution for this? — user543, Dec 27 '14 at 12:49

score -2 · Answer 2 · answered Apr 19 '13 at 04:35

-2

your problem may be related to the fact that your input is raw .h264. try using e.g. mp4box to mux it into a .mp4 file, then load the mp4 file with ffmpeg and try to seek to a keyframe again. e.g.:

mp4box -new -add my_file.h264 my_file.mp4

answered Apr 19 '13 at 04:35

njahnke

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Problem with ffmpeg function avformat_seek_file()

2 Answers2