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• Extract individual frames from video and pipe them to StandardOutput in FFmpeg

  13 novembre 2019, par Nicke Manarin

  I’m trying to extract frames from a video using FFmpeg. But instead of letting FFmpeg write the files to disk, I’m trying to get the frames directly from StandardOutput.

  I’m not sure if it’s feasible. I’m expecting to get each frame individually as they get decoded by reading and waiting until all frames are extracted.

  With the current code, I think that I’m getting all frames at once.

  ---

  Command

  ffmpeg -i "C:\video.mp4" -r 30 -ss 00:00:10.000 -to 00:01:20.000 -hide_banner -c:v png -f image2pipe -

  Code

  var start = TimeSpan.FromMilliseconds(SelectionSlider.LowerValue);
  
  var end = TimeSpan.FromMilliseconds(SelectionSlider.UpperValue);
  
  
  
  var info = new ProcessStartInfo(UserSettings.All.FfmpegLocation)
  
  {
  
      Arguments = $" -i \"{VideoPath}\" -r {fps} -ss {start:hh\\:mm\\:ss\\.fff} " +
  
          "-to {end:hh\\:mm\\:ss\\.fff} -hide_banner -c:v png -f image2pipe -",
  
      CreateNoWindow = true,
  
      ErrorDialog = false,
  
      UseShellExecute = false,
  
      RedirectStandardError = true,
  
      RedirectStandardOutput = true
  
  };
  
  
  
  var process = new Process();
  
  process.StartInfo = info;
  
  process.Start();
  
  
  
  while (!process.StandardOutput.EndOfStream)
  
  {
  
      if (_cancelled)
  
      {
  
          process.Kill();
  
          return;
  
      }
  
  
  
      //This returns me the entire byte array, of all frames.
  
      var bytes = default(byte[]);
  
      using (var memstream = new MemoryStream())
  
      {
  
          process.StandardOutput.BaseStream.CopyTo(memstream);
  
          bytes = memstream.ToArray();
  
      }
  
  }

  ---

  I also tried to use process.BeginOutputReadLine() and wait for each frame in OutputDataReceived. But it returns parts of each frame, like the 10 first bytes, than other 50 bytes, it’s erratic.

  Is there any way to get the frames separately via the output stream ?

• How to extract sequence of lossless images with FFMPEG and pipe them to mozjpeg's cjpeg ?

  7 novembre 2019, par Finch

  I know it can be down with imagemagick but mozjpeg produces much smaller images which is desirable.

  I want all frames of a video be extracted and converted to JPEG by mozjpeg.

  What I have tried :

  $ ind = 1
  
  $ ffmpeg -hide_banner -ss 00:00:10 -i IN.webm -t 00:00:02 -r 24 -c:v bmp -f image2pipe pipe:1 | \
  
      cjpeg - workDir/$((ind++)).jpeg

  Error message :

  av_interleaved_write_frame(): Broken pipe time=00:00:00.00 bitrate=N/A speed=   0x    
  
  
  
  Error writing trailer of pipe:1: Broken pipe
  
  
  
  frame=    1 fps=0.0 q=-0.0 Lsize=    6075kB time=00:00:00.04 bitrate=1194394.4kbits/s speed=0.0765x    
  
  
  
  video:6075kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%
  
  
  
  Conversion failed!

• python - tqdm progress bar on ffmpeg process with avs pipe

  9 octobre 2019, par MeSo2

  I am trying to implement a tqdm progress bar, but have no idea on how to do this when calling ffmpeg with check_output. (Most of the commands are set inside the avs file.)

  from subprocess import check_output
  
  check_output("ffmpeg -i \"temp_AVS.avs\" -c:v libx264 -b:v 25M -c:a aac 1.mp4", shell=True) 

  I cam across this Can ffmpeg show a progress bar ? but nothing hints on how to best implement it with my code.

  I also found this related post How to link the ffmpeg transcoding process information into a vb6 GUI app ?, and it look like I just need to call for the ffmpeg output. But I am note sure how to do that.