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• Pipe raw audio from mp4 using ffmpeg

  24 février 2015, par user1447257

  I have following class, that enables to read audio frames per video frame :

  class AudioAcquisition :
  ’’’
  This component returns an audio signal per video frame.
  ’’’

  def __init__(self, video_filename, bufsize=10**8):
  
      '''
  
      Parameters:
  
      -----------
  
  
  
      video_filename : String of the location of video file.
  
      '''
  
  
  
      # Read info from video using ffmpeg
  
      cmd = ["ffmpeg", \
  
          '-i', video_filename]
  
      info_pipe = subprocess.Popen(cmd, stdout=subprocess.PIPE, \
  
              stderr=subprocess.PIPE)
  
      _, err = info_pipe.communicate()
  
  
  
      self.__audio_fps = int(re.search('Stream[^\n]*Audio:[^\n]*, (\d*) Hz', err).group(1))
  
      self.__video_fps = int(re.search('Stream[^\n]*Video:[^\n]*, (\d*) fps', err).group(1))
  
  
  
      # Open audio using ffmpeg
  
      cmd = ['ffmpeg', \
  
          '-loglevel', 'quiet', \
  
          '-i', video_filename, \
  
          '-vn', \
  
          '-f', 's16le', \
  
          '-acodec', 'pcm_s16le', \
  
          '-ac', '1', \
  
          '-']
  
      print " ".join(cmd)
  
      self.__pipe = subprocess.Popen(cmd, stdout=subprocess.PIPE, \
  
          stderr=subprocess.STDOUT)
  
  
  
  def run(self):
  
      '''
  
      Yields:
  
      -------
  
  
  
      An audio signal per video frame.
  
      '''
  
  
  
      while (True):
  
          try:
  
              size = int(2 * self.__audio_fps / self.__video_fps)
  
              data = self.__pipe.stdout.read(size)
  
              if (len(data) < size):
  
                  break
  
              yield numpy.fromstring(data, dtype="int16")
  
          except IOError as e:
  
              print('Error encoutered while reading audio via ffmpeg: ' \
  
                  + str(e))
  
              break

  This somehow does not work properly, as the audio is dumped out with some noise frames at about 20s and repetitively occuring more often at later timestamps.

  Do you guys have any suggestions what I am missing in calling ffmpeg ?

  Thanks !

• ffmpeg Format settings, Matrix bt709

  22 mars 2023, par user1722669

  Does anyone know how I can achieve the following color space (bt.709) via FFmpeg ?
  
Here is what I have now in my files...

  



  

  



  As you can see there is Format settings, Matrix as default, how can I set it like this :

  



  

  • Format settings (Matrix) : Custom or Standard

  


  • Component Color primaries : BT.709

  


  • Transfer characteristics : BT.709

  


  • Matrix coefficients : BT.709

  


  



  Thank you

  


• difference between using SDL and using media player class that is videoview

  3 juin 2019, par Whoami

  I have been surfing the net for some time to get basic understanding of media framework in android. As part of this, to display video we have media player class or video view component which can easily display the video. When we have such solution provided by the framework itself, then why there are few components avaiable like SDL [ Simple Direct Media Layer], which claims the same functionality as video view ?

  How both are different ?