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• Create a pipe of input and output for wav to mp3 encoding

  28 octobre 2020, par loretoparisi

  I have to pipe a wave data stream to ffmpeg in Python. I can easily create an output pipe from an input mp3 file like :

  



         process = (
            ffmpeg
            .input(path)
            .output('pipe:', **output_kwargs)
            .run_async(pipe_stdout=True, pipe_stderr=True))
        buffer, _ = process.communicate()
        # because of we need (n_channels, samples)
        waveform = np.frombuffer(buffer, dtype='

  



  Here waveform will contain the wave audio file.

  



  Now, I want to pipe the same data, but from an input stream, but for some reason it does not work as expected :

  



      # data shape is like (9161728, 2) for two channels audio data
    input_kwargs = {'ar': sample_rate, 'ac': data.shape[1]} 
    output_kwargs = {'ar': sample_rate, 'strict': '-2'}
    n_channels = 2
    process = (
        ffmpeg
        .input('pipe:', format='f32le', **input_kwargs)
        .output('pipe:', **output_kwargs)
        .run_async(pipe_stdin=True, quiet=True))
    buffer, err = process.communicate(input=data.astype('code>

  



  The output buffer is empty here after getting the results from process.communicate, while err is

  



  Unable to find a suitable output format for 'pipe:'\npipe:: Invalid argument\n"


  


• 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!