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• Record audio data to an existing media file using FFMPEG API

  3 février 2021, par bbdd

  My task is to record the received audio data in a media file. I have no problem with this, everything works fine. But, when closing the audio file, I will no longer be able to re-open it and write the audio data to the end of the audio file. How do I solve this problem ? And in general, is it possible to write new data to the end of an existing media file ?

  


  This is a piece of code where I record the trailer and close the media file :

  


  // Writing the stream trailer to an output
// media file and free the file private data.
av_write_trailer(p_oFrmCtx);
avformat_close_input(&p_oFrmCtx);



  


• Matplotlib can not save animation

  1er avril 2020, par Justin Furuness

  I have a matplotlib animation and it will not save. If I do not save it, it runs totally fine and without error. When I try to save it errors with a message that is not helpful. I have googled this error and checked everything, but I cannot seem to find an answer to this problem. I have installed ffmpeg. Am I doing something wrong that is obvious ? I am running on ubuntu 19.10 with matplotlib 3.2.1 if that matters.

  



  The code to save the animation is below :

  



      def run_animation(self, total_rounds):
        anim = animation.FuncAnimation(self.fig, self.animate,
                                       init_func=self.init,
                                       frames=total_rounds * 100,
                                       interval=40,
                                       blit=True)
#        Writer = animation.writers['ffmpeg']
#        writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)
        anim.save('animation.mp4')


  



  The error traceback :

  



  2020-04-01 02:20:58,279-INFO: MovieWriter._run: running command: ffmpeg -f rawvideo -vcodec rawvideo -s 1200x500 -pix_fmt rgba -r 25.0 -loglevel error -i pipe: -vcodec h264 -pix_fmt yuv420p -y animation.mp4
Traceback (most recent call last):
  File "/home/anon/.local/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 2785, in _wait_cursor_for_draw_cm
    self.set_cursor(cursors.WAIT)
  File "/home/anon/.local/lib/python3.7/site-packages/matplotlib/backends/backend_gtk3.py", line 468, in set_cursor
    self.canvas.get_property("window").set_cursor(cursord[cursor])
AttributeError: 'NoneType' object has no attribute 'set_cursor'


  



  Thanks a million for your help

  


• Continously read file in Ruby and save into pipe

  7 juillet 2016, par stiller_leser

  I am trying to continously read a file and save the output into a IO.pipe. The motivation being that ffmpeg which has been spawned before and given the r-end of the pipe as STDIN will then convert the video.
  This is what I have so far :

      r,w = IO.pipe
  
      ffmpeg_args = ' -i pipe:0 "test.mp4"'
  
      pid = Process.spawn('ffmpeg'+ffmpeg_args, {STDIN => r, STDERR => STDOUT})
  
      Process.detach pid
  
      File.open(@options['filename'], 'rb') do |file|
  
        while line = file.gets
  
          w.write line.read
  
        end
  
      end

  I had success with declaring the input file directly as STDIN for the process, but this lead to an early termination of ffmpeg since it had reached the end of the file. With the code above ffmpeg complains about invalid data.

  Is there any way this could be achieved ?