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• Accord.Video.FFMpeg : Problem of duration difference between recording time and video time

  5 mars 2020, par ckrby

  I want to save the footage I get from the webcam as a video in webM (Vp8) format. I use the Accord library. But when recording, there is almost 2-3 times the difference between the time spent and the video time. The code I use and some debug outputs are below.

  Accord.Video.FFMpeg 3.8.2-Alpha (double pts/dts bug fixed version)
  Video Save Format : VP8 (.WebM)

  Record Start Settings :

  videoCodec = VideoCodec.Vp8;    
  
  bitrate : 1250000   
  
  framerate :10   
  
  height :720 
  
  width: 1280 
  
  videoSource.VideoResolution: 1280x720, 30 fps (30 max fps), 24 bpp  
  
  FileWriter.BitRate = bitRate;   
  
  FileWriter.FrameRate = new Accord.Math.Rational((int)framerate );   
  
  FileWriter.Width = width;   
  
  FileWriter.Height = height; 
  
  FileWriter.VideoCodec = videoCodec; 
  
  FileWriter.Open(FileName);  
  
  _recording = true;  
  
  StartTimeStamp = DateTime.Now;  

  newFrame Event

  private void VideoSourcePlayer1_NewFrame(object sender, ref Bitmap image)
  
  {
  
      if (_recording)
  
      {
  
          try
  
          {
  
              Bitmap CurrentBitmap = image;
  
              DateTime CurrentTimeStamp = DateTime.Now;
  
              TimeSpan CurrentTimeSpan = StartTimeStamp - CurrentTimeStamp;
  
              Console.WriteLine("Video Write Timespan: " + CurrentTimeSpan.ToString());
  
              FileWriter.WriteVideoFrame(CurrentBitmap, CurrentTimeSpan);
  
              // FileWriter.WriteVideoFrame(image);  
  
          }
  
          catch (Exception ex)
  
          {
  
              Console.WriteLine("VideoSourcePlayer1_NewFrame catch: " + ex.Message);
  
          }
  
      }
  
  }

  Note : It is the same issue with timespan or without timespan writing.

  In the 122 second (02.02 min) period, 50 seconds of video recording is created. I couldn’t solve it.

  Little Part of the debug output :

  Video Write Timespan : -00:01:55.4107365
  pts:4,730000e+004 pts_time:47,3 dts:4,730000e+004 dts_time:47,3 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:55.6136263
  pts:4,740000e+004 pts_time:47,4 dts:4,740000e+004 dts_time:47,4 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:55.8354960
  pts:4,750000e+004 pts_time:47,5 dts:4,750000e+004 dts_time:47,5 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:56.5161088
  pts:4,760000e+004 pts_time:47,6 dts:4,760000e+004 dts_time:47,6 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:56.7309841
  pts:4,770000e+004 pts_time:47,7 dts:4,770000e+004 dts_time:47,7 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:56.9758413
  pts:4,780000e+004 pts_time:47,8 dts:4,780000e+004 dts_time:47,8 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:57.1947200
  pts:4,790000e+004 pts_time:47,9 dts:4,790000e+004 dts_time:47,9 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:57.4375834
  pts:4,800000e+004 pts_time:48 dts:4,800000e+004 dts_time:48 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:01:57.5804983

  The last two outputs :

  Video Write Timespan : -00:02:02.7505463
  pts:5,000000e+004 pts_time : 50 dts:5,000000e+004 dts_time : 50 duration:1,000000e+002 duration_time:0,1
  Video Write Timespan : -00:02:02.9884038
  pts:5,010000e+004 pts_time : 50,1 dts:5,010000e+004 dts_time : 50,1 duration:1,000000e+002 duration_time:0,1

  Why is there a difference between timespan and dts/pts time ? Could the problem be due to this ?

  Note : When I set the framerate to 30 ; Another process 95 seconds (1.35 min) recording time is 16 seconds in the video.

  As the frame rate increases, the length of the video gets shorter and
  shorter than the actual value it should be.

  Output :

  Video Write Timespan : -00:01:35.1086178
  pts:1,606700e+004 pts_time : 16,067 dts:1,606700e+004 dts_time : 16,067 duration:3,300000e+001 duration_time:0,033
  Video Write Timespan : -00:01:35.2565302
  pts:1,610000e+004 pts_time : 16,1 dts:1,610000e+004 dts_time : 16,1 duration:3,300000e+001 duration_time:0,033
  Video Write Timespan : -00:01:35.3984494
  pts:1,613300e+004 pts_time : 16,133 dts:1,613300e+004 dts_time : 16,133 duration:3,300000e+001 duration_time:0,033

  So the video duration is like dts_time. Why is the video duration not
  value of timespan time, I still can’t find it ??

  Soory for my bad english & expression,

• Evolution #3560 : Supprimer l’option expérimentale Google Closure Compiler

  4 mai 2017, par b b

  Super, merci mignon :)

• H264 to MP4 with Bframe play back and forth on google chrome[ffmpeg]

  2 mai 2017, par Ravi Agola

  I want to generate a mp4 container with h264 encoded file.

  H264 file contains [I P B B][P B B][P B B][P B B] frames.

  when I generate a mp4 file with FFmpeg, It works well with FFplay as well as VLC but on google-chrome mp4 file plays frame back and forth.

  ffmpeg -i input.h264 -vcodec copy output.mp4

  when i use internal codec library(libx264) it works well on (ffplay,vlc and google-chrome)

  ffmpeg -i input.h264 -vcodec h264 output.mp4

  as above command transcode h264(native) to h264(x264), I don’t want to transcode file as I will be using it with ffmpeg library.

  when I use h264 without B frame it works well in both cases.

  I have tried some experiment with sample test file available here.

  direct conversion(MKV to MP4) works well with chrome as below

  ffmpeg -i jellyfish-3-mbps-hd-h264.mkv -vcodec copy output.mp4

  (MKV to H264 and H264 to MP4) plays back and forth on chrome

  ffmpeg -i jellyfish-3-mbps-hd-h264.mkv -vcodec copy output.h264
  ffmpeg -i output.h264 -vcodec copy output.mp4

  I get message in this case
  [mp4 @ 0xb6f8b20] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
  [mp4 @ 0xb6f8b20] pts has no value"

  what can be a reason behind this behavior ?

  Thanks.