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• ffmpeg determine frame number for fade filter

  16 juin 2016, par Gert Gottschalk

  I am looking for an easy way to set the time points for the fade filter. Particularly for the fade-out at the end. At best would be a time based format. I understand the fade filter works based on frames. But is there a way to change that to time stamp ? Particularly in the end I have a hard time getting the number of the last frame. Some means to tell the fade filter to start the fade 0.5sec before the end would be awesome. Maybe something like :

  -filter:v 'fade=out:-0.5:0.3'

  Read : ’start fade out 0.5sec before end and have fade take 0.3sec. I.e. have 0.2sec of black at the end.

  I would also be OK if this would be in frame number counts.

  My grief right now is that the frame count i.e. reported by ffprobe seems to be somewhat half of what it really is. A fade filter applied on the count provided by ffprobe turn my video to black about half-way through the clip. I’m not sure what I’m missing there.

  Again my primary question is : How to determine the correct frame number for the fade out filter ?

  Thanks,
  Gert

• How to determine when FFmpeg process completes

  18 avril 2017, par ajbeaven

  var origFilePath = "C:/MyOriginalFile.webm";
  
  var processedFilePath = "C:/MyProcessedFile.webm";
  
  
  
  RunFfmpeg($"-i \"{origFilePath}\" -af \"silenceremove=1:0.1:0.001, areverse, silenceremove=1:0.1:0.001, areverse\" \"{processedFilePath}\" -y");
  
  
  
  // fails with IOException as the file presumably not been released by FFmpeg
  
  System.IO.File.Delete(origFilePath);

  When the file is deleted, the following exception is frequently (maybe 80% of the time) thrown :

  IOException : The process cannot access the file ’C :\MyOriginalFile.webm’ because it is being used by another process.

  The call to create and run the FFmpeg process goes like this :

  private List<string> RunFfmpeg(string arguments)
  
  {
  
      using (var process = new Process())
  
      {
  
          process.StartInfo.RedirectStandardOutput = true;
  
          process.StartInfo.RedirectStandardError = true;
  
          process.StartInfo.FileName = _hostingEnvironment.ContentRootPath + _settings.FfmpegPath;
  
          process.StartInfo.Arguments = arguments;
  
          process.StartInfo.UseShellExecute = false;
  
          process.StartInfo.CreateNoWindow = true;
  
  
  
          // ffmpeg only uses strerr for its output
  
          var output = new List<string>();
  
          process.ErrorDataReceived += new DataReceivedEventHandler((s, e) => { 
  
              if (e.Data != null)
  
                  output.Add(e.Data);
  
          });
  
  
  
          process.Start();
  
          process.BeginErrorReadLine();
  
          process.WaitForExit();
  
          return output;
  
      }
  
  }
  
  </string></string>

  It appears that even though the process has completed when the file is deleted, FFmpeg is still processing or has otherwise not released it.

  Is this behaviour expected ? How do I go about ensuring that FFmpeg has finished processing the files before continuing ?

• FFmpeg-split.py can't determine video length

  13 juin 2017, par Almog Woldenberg

  First, I’m not a developer. I’m trying to split a movie into 1 minute clips usinf ffmpeg-split.py python script. I made sure FFmpeg is installed it trying a simple command and it worked like magic :

  ffmpeg -i soccer.mp4 -ss 00:00:00 -codec copy -t 10 soccer1.mp4

  A new video file was created in the same folder.

  I saved the FFmpeg-split.py in the same dir, updated python PATH and typed the following command :

  python ffmpeg-split.py -f soccer.mp4 -s 10

  what I got back was :

  can't determine video length

  I believe it just can’t find the file. I switched video files and even deleted it and got the same message.

  Any ideas ?