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• What is ffmpeg trying to do when fps is shown gradually decreasing for a given frame ?

  30 mars 2015, par eternalthinker

  I’ve been trying to create an animated overlay over an FLV video, and trying to get the output in MP4 format. I initially used ffmpeg version 1.26. But, as the filters seem to support better options with the latest format, I compiled ffmpeg version 2.61 from source.

  Now the encoding seems to work fine, but the command stays at one point for too long, where it is seen that the fps drops to smaller values, and the ’drop’ value changes accordingly. I used the fps filter to supply fps=25 option, and now the encoding is stuck at the same point, only the drop value remains 0, while fps is shown dropping to smaller values, taking a long time as before.

  

  In the screenshot above, all values remain same, while fps keep dropping to smaller values. After 10fps, it drops by 0.1 and continues past 1, to 0.9 etc. I didn’t wait until it went down further, as the whole thing was taking too much time.

  What can I do to avoid this, and tell ffmpeg to move on with one framerate ? That is, to finish encoding after the 21.45 seconds shown here, and not try to tweak fps or whatever it is trying to do here.

  The full command I am using is this :

  ffmpeg -y -i BaseVideo.flv  -loop 1 -i 1overlay.png  -loop 1 -filter_complex '[1:v] fade=out:20:20:alpha=1:start_time=4:d=3:c=white [V2]; [0:v][V2] overlay, fps=25' -c:v libx264 -strict -2 result.mp4

• Using ffmpeg to create a video from a sequence of TGA images, with a depth of field blur effect sourced from the TGA's alpha channel

  19 mars 2016, par vpvp

  I’m working on turning a sequence of TGA images into a video using ffmpeg. I want the video to have a depth of field blur effect. The alpha channel of each TGA contains a depth-mask, where black=close and white=far. I want to use this info to add DOF blur to the final output of that frame. After searching, the closest answer I could find was this
  http://superuser.com/questions/916431/ffmpeg-filter-to-boxblur-and-greyscale-a-video-using-alpha-mask, but it is for a static dof-mask. The DOF mask I would be using is obviously changing every frame, and an alpha channel instead of a seperate png.

  Here is my current cmd line

  ffmpeg -framerate 60 -i image.%10d.tga -c:v libx264 -preset slow -crf 0 -c:a copy -pix_fmt yuv420p output0.mp4

  It seems the answer would involve some use of alphamerge/alphaextract/boxblur, but I’m brand new to ffmpeg so I don’t know how to formulate the command.

  Thanks in advance.

• ffmpeg from a C# app using Process class - user prompt not shown in standardError

  21 avril 2016, par DarwinIcesurfer

  I am writing an app to run ffmpeg using c#. My program redirects the standardError output to a stream so it can be parsed for progress information.

  During testing I have found a problem :

  If the output is shown in a command window rather than being redirected ffmpeg will display it’s normal headers followed by "file c :\temp\testfile.mpg already exists. overwrite [y]". If I click on the command window and press y the program continues to encode the file.

  If the StandardError is redirected to my handler and then printed to the console, I see the same header information that was displayed in the command window now printed to the console. except for the file...already exists prompt. If I click in the command window and press y the program continues to process the file.

  Is there a stream other than standardOutput or standardError that is used when the operator is prompted for information, or am I missing something else ?

  public void EncodeVideoWithProgress(string filename, string arguments, BackgroundWorker worker, DoWorkEventArgs e)
  
      {
  
  
  
          Process proc = new Process();
  
  
  
          proc.StartInfo.FileName = "ffmpeg";
  
          proc.StartInfo.Arguments = "-i " + " \"" + filename + "\" " + arguments;
  
  
  
          proc.StartInfo.UseShellExecute = false;
  
          proc.EnableRaisingEvents = true;
  
  
  
          proc.StartInfo.RedirectStandardError = true;
  
          proc.StartInfo.RedirectStandardOutput = false;
  
          proc.StartInfo.CreateNoWindow = false; //set to true for testing
  
  
  
          proc.ErrorDataReceived += new DataReceivedEventHandler(NetErrorDataHandler);
  
  
  
          proc.Start();
  
          proc.BeginErrorReadLine();
  
  
  
  
  
          StreamReader reader = proc.StandardOutput;
  
           string line;
  
           while ((line = reader.ReadLine()) != null)
  
          { Console.WriteLine(line); }
  
       proc.WaitForExit();
  
  }
  
  
  
  private static void NetErrorDataHandler(object sendingProcess,
  
                 DataReceivedEventArgs errLine)
  
      {
  
          if (!String.IsNullOrEmpty(errLine.Data))
  
          {
  
              Console.WriteLine(errLine.Data);
  
          }
  
      }