Recherche avancée

Sur d’autres sites (7212)

• lavc/fic : Be less verbose for invisible cursor outside of video.

  1er mai 2016, par Carl Eugen Hoyos

  lavc/fic : Be less verbose for invisible cursor outside of video.
  

  • [DH] libavcodec/fic.c

• gdigrab : fix gdi object leak if using mouse

  19 août 2014, par rogerdpack

  gdigrab : fix gdi object leak if using mouse
  based on patch from hlszl1983@163.com
  Signed-off-by : rogerdpack <rogerpack2005@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavdevice/gdigrab.c

• FFmpeg - Lost in the hell of av_seek_frame()

  14 octobre 2022, par Jean-Milost Reymond

  I'm writing a video player which uses FFmpeg. I need to implement a seek functionality.

  


  So I implemented a seek function (see code below) which I tested against a video with a duration of 2,8s :

  



  static void seek_to(AVFormatContext* fmt, int64_t pos)
{
    AVStream* stream = fmt->streams[0];
    int64_t   seek_pos = pos;
    int       seek_flags;

    if (fmt->duration == AV_NOPTS_VALUE)
        seek_flags = AVSEEK_FLAG_FRAME;
    else
        seek_flags = AVSEEK_FLAG_BACKWARD;

    AVRational time_base = { 1, AV_TIME_BASE };

    int64_t seek_target = seek_flags == AVSEEK_FLAG_BACKWARD ?
            av_rescale_q(seek_pos, time_base, stream->time_base) : seek_pos;

    int ret = av_seek_frame(fmt, 0, seek_target, seek_flags);

    if (ret < 0)
    {
        // log the error...
    }

    ...

    // perform some tasks like flushing the decoder(s) by calling the mp_decode_flush() function
}


  


  I certify that the pos value is well passed in microseconds (it's the format expected by AV_TIME_BASE and matching with the duration exposed in format context - I strongly checked it), and contains a valid number between 0 and the video duration time.

  


  As a result, the seek roughly works, however it is very choppy and ugly. It's like the video contained only 3 possible position (0, 1/3 and 2/3 of the total length) and there is no way to have a smooth and precise seek position.

  


  I suspect a conversion issue somewhere (as if the final value was in seconds instead of microseconds), but I cannot figure out what I'm doing wrong.

  


  My assumptions are :

  


  

  • I have effectively a conversion issue, but I strongly tested all my values and I can certify that they are passed in the expected ranges and well converted in the correct time bases. So the issue would be on the FFmpeg side

  


  • The FFmpeg library is not planned to work well with so small values, it needs at least a huger video to works well

  


  • I'm doing something wrong, and perhaps my approach isn't the good one to seek in my videos

  


  


  Is one of my above assumptions correct, or there is something else which may break my seek function ? Has someone already faced a such issue and how he resolved it ?