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• FFmpeg pauses the extraction of frames at 20% (but when closed, dumps all frames to disk)

  1er décembre 2019, par Nicke Manarin

  I’m trying to extract frames from a video using FFmpeg. I want to be able to control which frames to extract, by setting the start, end and FPS values.

  The problem is, that after the extraction begins, FFmpeg stops after 20% of the way. It always stops there, independently of the frame count.

  This is the code that I’m using :

  var start = TimeSpan.FromMilliseconds(SelectionSlider.LowerValue);
  
  var end = TimeSpan.FromMilliseconds(SelectionSlider.UpperValue);
  
  var fps = FpsIntegerUpDown.Value;
  
  var count = CountFrames(); //Duration x FPS
  
  var folder = Path.Combine(RootFolder, "Import");
  
  var path = Path.Combine(folder, $"%0{count.ToString().Length + 1}d.png");
  
  
  
  try
  
  {
  
      //Create temporary folder.
  
      if (Directory.Exists(folder))
  
          Directory.Delete(folder, true);
  
  
  
      Directory.CreateDirectory(folder);
  
  
  
      CaptureProgressBar.Value = 0;
  
      CaptureProgressBar.Maximum = count;
  
  
  
      var info = new ProcessStartInfo(UserSettings.All.FfmpegLocation)
  
      {
  
          Arguments = $" -i \"{VideoPath}\" -vsync 2 -progress pipe:1 -vf scale={VideoWidth}:{VideoHeight} -ss {start:hh\\:mm\\:ss\\.fff} -to {end:hh\\:mm\\:ss\\.fff} -hide_banner -c:v png -r {fps} -vframes {count} \"{path}\"",
  
          CreateNoWindow = true,
  
          ErrorDialog = false,
  
          UseShellExecute = false,
  
          RedirectStandardError = true,
  
          RedirectStandardOutput = true
  
       };
  
  
  
       _process = new Process();
  
       _process.OutputDataReceived += (sender, e) =>
  
       {
  
           Debug.WriteLine(e.Data);
  
  
  
           if (string.IsNullOrEmpty(e.Data))
  
               return;
  
  
  
           var parsed = e.Data.Split('=');
  
  
  
           switch (parsed[0])
  
           {
  
               case "frame":
  
                   Dispatcher?.InvokeAsync(() => { CaptureProgressBar.Value = Convert.ToDouble(parsed[1]); });
  
                   break;
  
  
  
               case "progress":
  
                   if (parsed[1] == "end" && IsLoaded)
  
                       GetFiles(folder); //Get all files from the output folder.
  
  
  
                   break;
  
            }
  
      };
  
  
  
  _process.ErrorDataReceived += (sender, e) =>
  
  {
  
      if (!string.IsNullOrEmpty(e.Data))
  
          throw new Exception("Error while capturing frames with FFmpeg.") { HelpLink = $"Command:\n\r{info.Arguments}\n\rResult:\n\r{e.Data}" };
  
  };
  
  
  
  _process.StartInfo = info;
  
  _process.Start();
  
  _process.BeginOutputReadLine();
  
  
  
  //Just to wait...
  
  await Task.Factory.StartNew(() => _process.WaitForExit());

  So, after starting the import process, FFmpeg will extract some frames, and after reaching around 20%, it will pause the extraction.

  frame=95
  
  fps=5.79
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1400000
  
  out_time_ms=1400000
  
  out_time=00:00:01.400000
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.0854x
  
  
  
  progress=continue
  
  frame=106
  
  fps=6.25
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1583333
  
  out_time_ms=1583333
  
  out_time=00:00:01.583333
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.0933x
  
  progress=continue
  
  
  
  frame=117
  
  fps=6.67
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1766667
  
  out_time_ms=1766667
  
  out_time=00:00:01.766667
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.101x
  
  progress=continue

  Something strange : if I close the app while is the extraction is paused, suddenly FFmpeg will dump all frames to the folder.

  Why would FFmpeg pause the extraction at all (But continue doing in memory) ?
  Is there any way for me to force FFmpeg to extract the frames normally ?

  PS : It does not happen while using FFmpeg via cmd, so it must be something in code.

• How to save (record) rtsp stream to the disk storage without artifacts and missing seconds ?

  20 septembre 2019, par Bogdan Rudnytskyi

  I need to save (record) rtsp stream to the disk storage.
  I am using nginx-module and ffmpeg for it.
  Here the config for enable recording :

  rtmp {
  
      live on;
  
      hls on;
  
      hls_fragment 5s;
  
      server {
  
          listen 1935;
  
          application cam1 {
  
              hls_path /tmp/cam1;
  
          }
  
          exec_static ffmpeg -rtsp_transport tcp -i rtsp://... -c copy -f flv rtmp://.../cam1/stream;
  
      }
  
  }

  Config is creating the flv files, each duration of 5 second.
  Then we need to merge all got files in one file by command :

  ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.flv

  After concated files we are got a problem. When previous 5 seconds end and start next 5 seconds we have artifacts and missing 0.5-1 second.

  Please, get me help with saving rtsp stream without artifacts and missing seconds.

• Although ffmpeg installed, unable to save mp4 file on disk

  2 janvier 2020, par yannis

  Although I have installed ffmpeg, matplotlib reports that MovieWriter ffmpeg is unavailable and the MP4 file created is empty.

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  
  
  # First set up the figure, the axis, and the plot element we want to animate
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  # initialization function: plot the background of each frame
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  # animation function.  This is called sequentially
  
  def animate(i):
  
      x = np.linspace(0, 2, 1000)
  
      y = np.sin(2 * np.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  # call the animator.  blit=True means only re-draw the parts that have changed.
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  # save the animation as an mp4.  This requires ffmpeg or mencoder to be
  
  # installed.  The extra_args ensure that the x264 codec is used, so that
  
  # the video can be embedded in html5.  You may need to adjust this for
  
  # your system: for more information, see
  
  # http://matplotlib.sourceforge.net/api/animation_api.html
  
  anim.save('basic_animation.mp4', fps=30, extra_args=['-vcodec', 'libx264'])
  
  
  
  plt.show()

  I have even added the line plt.switch_backend('TkAgg') proposed in another post, nothing changed. Here is my matplotlib :

  Name: matplotlib
  
  Version: 2.1.0
  
  Summary: Python plotting package
  
  Home-page: http://matplotlib.org

  my ffmpeg :

  Name: ffmpeg
  
  Version: 1.4
  
  Summary: ffmpeg python package url [https://github.com/jiashaokun/ffmpeg]
  
  Home-page: https://github.com/jiashaokun/ffmpeg

  and my Python version :

  Python 3.6.5

  The error I get is :

  /usr/local/lib/python3.6/site-packages/matplotlib/animation.py:1218: UserWarning: MovieWriter ffmpeg unavailable
  
    warnings.warn("MovieWriter %s unavailable" % writer)

  This error has been reported many times on stackoverflow, each time the solution is either to install ffmpeg (mine is installed) or to add that extra line about the backend, which hasn’t changed anything for me.

  Curiously enough the plt.show()command works and I do preview an animation, but the only file format to save it is (nonanimated) PNG.