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• Get frame time in ffmpeg

  30 mai 2023, par Srv19

  I am trying to make a little video player that has seek bar (with ffmpeg, of course). For that i need function that will, using data from frame and/or packet, get me current time in the video that should be set in seek slider.

  


  It should work like this :

  


  my_time = get_cur_time()
seek(my_time + 10)
assert(my_time+10 == get_cur_time())
seek(my_time - 10)
assert(my_time-10 == get_cur_time())


  


  I do understand that ffmpeg does not support precise seeking, so equality here means "something reasonably close".

  


  What code have i used for this thus far :

  


  frame_time = frame->pts * av_q2d(video_dec_ctx->time_base) * 1000;


  


  where frame is AVFrame and video_dec_ctx is AVCodecContext.

  


  And for seeking :

  


  int fn = ffmpeg::av_rescale(tsms,fmt_ctx->streams[video_stream->index]->time_base.den,
                            fmt_ctx->streams[video_stream->index]->time_base.num);
int frame = fn / 1000;

printf("\t avformat_seek_file to %d\n",frame);
int flags = AVSEEK_FLAG_FRAME;
if (frame < this->frame->pts)
    flags |= AVSEEK_FLAG_BACKWARD;
if (ffmpeg::av_seek_frame(fmt_ctx, video_stream->index, frame, flags))
{
    printf("\nFailed to seek for time %d",frame);
    return false;
}

avcodec_flush_buffers(video_dec_ctx);
int got_frame = 0;
do
if (av_read_frame(fmt_ctx, &pkt) >= 0) {
    decode_packet_ro(&got_frame, 0);
    av_free_packet(&pkt);
}
else
{
    read_cache = true;
    pkt.data = NULL;
    pkt.size = 0;
    break;
}
while (!(got_frame && this->frame->pts >= frame));


  


  The code does forward seeking passably, but after any attempt of backward seeking my second assertion fails. After seeking to previous position, my method of getting time does not return position less that one before seeking. That causes my seek slider to work grossly incorrectly.

  


• FFmpeg for marking time video based on a reference date

  3 août 2016, par Denio Mariz

  I am trying to mark a timestamp in a video using Drawtext filter.
  FFmpeg easily marks timestamps based on localtime, gmtime or even PTS. However, I want to assign a reference time (start time) for the timestamp in order to represent the time the video was recorded (not encoded).

  Reading the documentation, I found that option "basetime" can be used for this purpose. However it seems that is not working or I am missing something.

  The command line I am using is :

  ffmpeg -y -i input.mp4 -filter_complex drawtext="fontfile=/tmp/UbuntuMono-B.ttf: fontsize=36: fontcolor=yellow: box=1: boxcolor=black@0.4: text='Wall Clock Time\: %{gmtime\:%Y-%m-%d %T}': basetime=1456007118" output.mp4

  By using basetime=1456007118", it was expected the start time was set to ’02/20/2016 20:25:18’ since 1456007118 is the UTC time for that time and date :

  date -d '02/20/2016 20:25:18' +"%s" # format MM/DD/AAAA hh:mm:ss
  
  1456007118

  However, no error is issued by FFMpeg and the video is marked with current GMT, ignoring "basetime" option.

  Any hint ?
  Thanks.

  Complete information about FFmpeg version and output is :

     ffmpeg -y -i /home/denio/Videos/Interstellar_2014_Trailer_4_5.1-1080p-HDTN.mp4 -filter_complex drawtext="fontfile=/tmp/UbuntuMono-B.ttf: fontsize=36: fontcolor=yellow: box=1: boxcolor=black@0.4: text='Wall Clock Time\: %{gmtime\:%Y-%m-%d %T}': basetime=1470226363" /tmp/x.mp4
   ffmpeg version 3.1.1 Copyright (c) 2000-2016 the FFmpeg developers
     built with gcc 5.3.1 (Ubuntu 5.3.1-14ubuntu2.1) 20160413
     configuration: --enable-libxavs --enable-bzlib --enable-libfaac --enable-libfreetype --enable-libfontconfig --enable-libmp3lame --enable-libschroedinger --enable-libspeex --enable-libvorbis --enable-libx264 --enable-libx265 --enable-libxvid --enable-zlib --enable-x11grab --enable-static --enable-pthreads --enable-gpl --enable-nonfree --enable-version3 --disable-ffserver --enable-libgsm --enable-librtmp --enable-libvpx --enable-libschroedinger --enable-libopencore-amrnb --enable-libopenjpeg
     libavutil      55. 28.100 / 55. 28.100
     libavcodec     57. 48.101 / 57. 48.101
     libavformat    57. 41.100 / 57. 41.100
     libavdevice    57.  0.101 / 57.  0.101
     libavfilter     6. 47.100 /  6. 47.100
     libswscale      4.  1.100 /  4.  1.100
     libswresample   2.  1.100 /  2.  1.100
     libpostproc    54.  0.100 / 54.  0.100
   ...
   ...

• FFmpeg - calculate the remaining conversion time

  27 avril 2017, par MPM Уеб Дизайн

  I use ffmpeg to convert a clip video.mp4 to video.mp3 for example.
  Is there a way to calculate the remaining conversion time ?