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• Running "FFMPEG" for several times in winfoms

  13 novembre 2015, par Ahmad

  In a C# Windows application, I try to call "ffmpeg" to multiplex video and audio. It may be called several times. In the first call, everything is fine, but in the next call I have some problems. One problem is that the earlier "ffmpeg" process isn’t closed. So, I tried to kill it if it exists. but now I got an error for a disposed object in the following code :

     public static void FFMPEG3(string exe_path, string avi_path, string mp3_path, string output_file)
  
      {
  
          const int timeout = 2000;
  
          Kill(exe_path);
  
          using (Process process = new Process())
  
          {
  
              process.StartInfo.FileName = exe_path;
  
              process.StartInfo.Arguments = string.Format(@"-i ""{0}"" -i ""{1}"" -acodec copy -vcodec copy ""{2}""",
  
                                             avi_path, mp3_path, output_file);
  
              process.StartInfo.UseShellExecute = false;
  
              process.StartInfo.CreateNoWindow = true;
  
              process.StartInfo.RedirectStandardOutput = true;
  
              process.StartInfo.RedirectStandardError = true;
  
  
  
              StringBuilder output = new StringBuilder();
  
              StringBuilder error = new StringBuilder();
  
  
  
              using (AutoResetEvent outputWaitHandle = new AutoResetEvent(false))
  
              using (AutoResetEvent errorWaitHandle = new AutoResetEvent(false))
  
              {
  
                  process.OutputDataReceived += (sender, e) =>
  
                  {
  
                      if (e.Data == null)
  
                      {
  
                          outputWaitHandle.Set();
  
                      }
  
                      else
  
                      {
  
                          output.AppendLine(e.Data);
  
                      }
  
                  };
  
                  process.ErrorDataReceived += (sender, e) =>
  
                  {
  
                      if (e.Data == null)
  
                      {
  
                          errorWaitHandle.Set();
  
                      }
  
                      else
  
                      {
  
                          error.AppendLine(e.Data);
  
                      }
  
                  };
  
  
  
                  process.Start();
  
  
  
                  process.BeginOutputReadLine();
  
                  process.BeginErrorReadLine();
  
  
  
                  if (process.WaitForExit(timeout) &&
  
                      outputWaitHandle.WaitOne(timeout) &&
  
                      errorWaitHandle.WaitOne(timeout))
  
                  {
  
                      // Process completed. Check process.ExitCode here.
  
                      process.Close();
  
                  }
  
                  else
  
                  {
  
                      // Timed out.
  
                      process.Close();
  
                  }
  
              }
  
          }
  
      }

  I get ObjectDisposedException for ErrorDataRecieved event on errorWaitHandle.Set();

  First, I want to resolve this error, but if you know any better solution to run the "ffmpeg" for several times please suggest me.

• FFmpeg - Multiple videos with 4 areas and different play times

  25 mai 2018, par Robert Smith

  I have videos as follows

  video   time
  
  ======= =========
  
  Area 1:
  
  video1a    0-2000
  
  video1b 2500-3000
  
  video1c 3000-4000
  
  
  
  Area 2:
  
  video2a  300- 400
  
  video2b  800- 900
  
  
  
  Area 3:
  
  video3a  400- 500
  
  video3b  700- 855
  
  
  
  Area 4:
  
  video4a  400- 500
  
  video4b  800- 900

  Basically these are security camera outputs and should display in 4 areas :

  So far I have the following :

  ffmpeg
  
      -i 1.avi -i 2.avi -i 3.avi -i 4.avi
  
      -filter_complex "
  
          nullsrc=size=640x480 [base];
  
          [0:v] setpts=PTS-STARTPTS, scale=320x240 [upperleft];
  
          [1:v] setpts=PTS-STARTPTS, scale=320x240 [upperright];
  
          [2:v] setpts=PTS-STARTPTS, scale=320x240 [lowerleft];
  
          [3:v] setpts=PTS-STARTPTS, scale=320x240 [lowerright];
  
          [base][upperleft] overlay=shortest=1 [tmp1];
  
          [tmp1][upperright] overlay=shortest=1:x=320 [tmp2];
  
          [tmp2][lowerleft] overlay=shortest=1:y=240 [tmp3];
  
          [tmp3][lowerright] overlay=shortest=1:x=320:y=240
  
      "
  
      -c:v libx264 output.mp4

  But there are two things I am missing :

  • The above is only for 4 video files, I need a way to add additional files to each area (for example video1b should play at its corresponding time after video1a in the same area)
  • How do I specify the beginning/ending time as shown above for each file ?

• Fast seeking ffmpeg multiple times for screenshots

  14 septembre 2021, par user3786834

  I have come across https://askubuntu.com/questions/377579/ffmpeg-output-screenshot-gallery/377630#377630, it's perfect. That has done exactly what I wanted.

  



  However, I'm using remote URLs to generate the screenshot timeline. I do know it's possible to fast seek with remote files using https://trac.ffmpeg.org/wiki/Seeking%20with%20FFmpeg (using -ss before the -i) but this only runs the once.

  



  I'm looking for a way to use the

  



  ./ffmpeg -i input -vf "select=gt(scene\,0.4),scale=160:-1,tile,scale=600:-1" \
-frames:v 1 -qscale:v 3 preview.jpg


  



  command but using the fast seek method as it's currently very slow when used with a remote file. I use PHP but I am aware that a C method exists by using av_seek_frame, I barely know C so I'm unable to implement this into a PHP script I'm writing. So hopefully, it is possible to do this directly with ffmpeg in the PHP system() function.

  



  Currently, I run seperate ffmpeg commands (with the -ss method) and then combine the screenshots together in PHP. However, with this method it will be refetching the metadata each time and a more optimized method would be to have it all happen in the same command line because I want to reduce the amount of requests made to the remote url so I can run more scripts in sequence with each other.

  



  Thank you for your help.