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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 to add additional metadata to individual frames, DDB's, when creating an AVI file with ffmpeg

  6 décembre 2019, par Totte Karlsson

  I’m creating avi videos from device dependent bitmaps, DDB’s.

  The pipeline is quite simple, a GigE camera provides frame by frame, and each frame, a DDB, is piped to a ffmpeg process creating a final AVI file, using h264 compression.

  These videos are scientific in nature, and we would like to store/embed experimental hardware information, such as the states of a few digital lines, with each frame.
  This information need to be available in the final avi video

  Question is, is this possible ?

  Looking at this : https://docs.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmap it does not seem that adding additional data to the DDB themselves is possible, but I’m not sure.

• Why my youtube video made with ffmpeg only shows 360P and 1080P on mobile devices but works fine on desktop ?

  1er janvier 2020, par CheeseWithMe

  I am trying to create a video from an image and sound file with ffmpeg.

  This is what I use :

  ffmpeg -y -loop 1 -r 6  -i current_image.png -i current_audio.wav -shortest -c:v libx264 -preset ultrafast -tune stillimage -pix_fmt yuv420p -c:a aac out.mp4

  But uploading this on youtube will display only in 360P and 1080P on mobile devices while on Desktop I have all the resolutions up to 1080P.

  It has the same effect with the command from FFmpeg wiki on enconding from youtube

  ffmpeg -loop 1 -framerate 2 -i input.png -i audio.m4a -c:v libx264 -preset medium -tune stillimage -crf 18 -c:a copy -shortest -pix_fmt yuv420p output.mkv

  I have no idea why is this happening, I could use some guidance.