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• DVD Conversion with ffpmpeg-python

  10 décembre 2019, par Colin Bitterfield

  I am trying to convert in a programmatically DVD VOB files into an MP4. Then use scene detect to process the scenes.

  Does anyone know how to take a list of files and concat them using FFmpeg ?

  This code isn’t working but I am sure that it is close. I am not sure to use a concat filter or output_merge.

  import os
  
  import ffmpeg
  
  import glob
  
  
  
  vob_stream=[]
  
  for vob in vob_files:
  
      vob_stream.append(ffmpeg.input(vob))
  
  
  
  (
  
      ffmpeg
  
      .concat(
  
          .in_file(vob_stream)
  
      )
  
      .output(vob_out)
  
      .overwrite_output()
  
      .run(capture_stdout=True, capture_stderr=True,)
  
  
  
  )

• my ffmpeg stops streaming after a few seconds

  16 février 2015, par Andrew Simpson

  This is all new to me.

  I am using ffmpeg in my c# desktop app.

  The idea is to use the Process under C# to start ffmpeg on the DOS prompt.

  I then parse each bit of data to ’split’ off my jpegs.

  But after a few seconds the feed just stops.

  This is my code :

   private void button1_Click(object sender, EventArgs e)
  
      {
  
          try
  
          {
  
              Process process = new Process();
  
              FileStream baseStream = null;
  
  
  
              string arguments = @" -i rtsp://admin:admin@192.168.0.8:554/video_1 -an -f image2pipe -vf fps=fps=6 -qscale 0 -";
  
              string file = @"C:\bin\ffmpeg.exe";
  
              process.StartInfo.FileName = file;
  
              process.StartInfo.Arguments = arguments;
  
              process.StartInfo.CreateNoWindow = true;
  
              process.StartInfo.RedirectStandardError = true;
  
              process.StartInfo.RedirectStandardOutput = true;
  
              process.StartInfo.UseShellExecute = false;
  
  
  
              Task.Run(() =>
  
              {
  
                  try
  
                  {
  
                      process.Start();
  
                      byte[] buffer = new byte[200000];
  
                      //var error = process.StandardError.ReadToEnd();
  
                      //var error = process..ReadToEnd();
  
  
  
                      baseStream = process.StandardOutput.BaseStream as FileStream;
  
                      bool gotHeader = false;
  
                      bool imgFound = false;
  
                      int counter = 0;
  
                      while (true)
  
                      {
  
                          byte bit1 = (byte)baseStream.ReadByte();
  
                          buffer[counter] = bit1;
  
  
  
                          if (bit1 == 217 && gotHeader)
  
                          {
  
                              if (buffer[counter - 1] == 255)
  
                              {
  
                                  byte[] jpeg = new byte[counter];
  
                                  Buffer.BlockCopy(buffer, 0, jpeg, 0, counter);
  
                                  using (MemoryStream ms = new MemoryStream(jpeg))
  
                                  {
  
                                      pictureBox1.Image = Image.FromStream(ms);
  
                                      ms.Close();
  
                                  }
  
                                  imgFound = true;
  
                              }
  
                          }
  
                          else if (bit1 == 216)
  
                          {
  
                              if (buffer[counter - 1] == 255)
  
                              {
  
                                  gotHeader = true;
  
                              }
  
                          }
  
                          if (imgFound)
  
                          {
  
                              counter = 0;
  
                              buffer = new byte[200000];
  
                              imgFound = false;
  
                              gotHeader = false;
  
                          }
  
                          else
  
                          {
  
                              counter++;
  
                          }
  
                      }
  
                  }
  
                  catch (Exception ex2)
  
                  {
  
                      //log error here
  
                  }
  
              });
  
          }
  
          catch (Exception ex)
  
          {
  
              //log error here
  
          }
  
      }

  Like I said it works but then just stops.

  Is there something I should be mindful of ?

  Finally, is there a was to specify the quality of the jpeg ?

  NOTE
  I have already tried this just in the DOS Prompt and that also ’freezes’ after a few seconds.

• Why are there multiple timescale specified in a MP4/AVC container file ?

  24 juin 2021, par Lexx32117

  I am currently parsing a MPEG-DASH stream initialization segment (generated by FFMPEG) and I noticed that the timescale is specified at multiple different places in my file :

  


  

  • In the movie header box (mvhd) : 1000

  


  • In the media header box of my video track (mdhd) : 15360

  


  • In the AVC Configuration box (avcC) more precisely in the VUI section of the sequence parameter set NAL unit : 60

  


  


  Why is it specified in so many different places ? Why do they have different values ? Is there a hierarchy in these value ? For example does 60 overrides 15360 and 15360 overrides 1000 ?

  


  Here's the command I used to generate the file I am looking at :

  


  ffmpeg -f v4l2 -pixel_format yuyv422 -vcodec rawvideo -framerate 30 -video_size 640x360 -i /dev/video0 \
        -f dash -remove_at_exit false -use_template true -use_timeline true -streaming true -window_size 5 -extra_window_size 5 -seg_duration 5 -vcodec libx264 -b:v 1M -maxrate 1M -bufsize 2M  -pix_fmt yuv420p -r 30 -s 640x360 -aspect 16:9 /var/www/html/media/live.mpd