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• avformat/matroskaenc : do not write timebase as framerate

  28 avril 2018, par wm4

  avformat/matroskaenc : do not write timebase as framerate
  If the API user doesn't set avg_frame_rate, matroskaenc will write the
  
  current timebase as "default duration" for the video track. This makes
  
  no sense, because the "default duration" implies the framerate of the
  
  video. Since the timebase is forced to 1/1000, this will make the
  
  resulting file claim 1000fps.
  Drop it and don't write the element. It's optional, so it's better not
  
  to write it if the framerate is unknown.
  Strangely does not require FATE changes.
  

  • [DH] libavformat/matroskaenc.c

• error when running "imageio.plugins.ffmpeg.download()"

  14 juin 2018, par Maryeveh

  I am trying to run the command imageio.plugins.ffmpeg.download() after installing moviepy and imageio and importing imageio without error.
  I keep getting the following error and cannot figure out the solution :

  Imageio: 'ffmpeg-osx-v3.2.4' was not found on your computer; downloading it now.
  
  Error while fetching file: <urlopen error="error" certificate="certificate" verify="verify" failed="failed">.
  
  Error while fetching file: <urlopen error="error" certificate="certificate" verify="verify" failed="failed">.
  
  Error while fetching file: <urlopen error="error" certificate="certificate" verify="verify" failed="failed">.
  
  Error while fetching file: <urlopen error="error" certificate="certificate" verify="verify" failed="failed">.
  
  
  
      ---------------------------------------------------------------------------
  
      IOError                                   Traceback (most recent call last)
  
       in <module>()
  
            3 get_ipython().magic(u'matplotlib inline')
  
            4 import imageio
  
      ----> 5 imageio.plugins.ffmpeg.download()
  
            6 import matplotlib
  
            7 import matplotlib.pyplot as plt
  
  
  
      /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/imageio/plugins/ffmpeg.pyc in download(directory, force_download)
  
          71     get_remote_file(fname=fname,
  
           72                     directory=directory,
  
      ---> 73                     force_download=force_download)
  
          74 
  
          75 
  
  
  
      /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/imageio/core/fetching.pyc in get_remote_file(fname, directory, force_download, auto)
  
        125             return filename
  
         126     else:  # pragma: no cover
  
     --> 127         _fetch_file(url, filename)
  
         128         return filename
  
         129 
  
  
  
      /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/imageio/core/fetching.pyc in _fetch_file(url, file_name, print_destination)
  
          181         raise IOError('Unable to download %r. Perhaps there is a no internet '
  
          182                       'connection? If there is, please report this problem.' %
  
      --> 183                       os.path.basename(file_name))
  
          184 
  
          185 
  
  </module></urlopen></urlopen></urlopen></urlopen>

  IOError : Unable to download ’ffmpeg-osx-v3.2.4’. Perhaps there is a
  no internet connection ? If there is, please report this problem.

  I tried all the solutions I could think of or/and found online, including the ones described here ffmpeg installation on macOS for MoviePy fails with SSL error, but nothing helped.
  Does anyone found another solution ?

  Thanks

• ffmpeg in "streaming mode" suddenly stops writing output file and resumes after several minutes

  29 juin 2018, par EliA

  I’m using ffmpeg to convert chunks of media in webm format to a wav file in a "continuous stream" mode.

  Using a python wrapper, I’m feeding ffmpeg a webm chunk (let’s say 1 chunk each second) and ffmpeg continuously writes the output wav (then, in a separate thread I’m reading this wav file and pass the new data forward).

  This works well most of the time, but some times, I get this weird behavior :

  • after some chunks are processed and output to the wav file, ffmpeg stops writing to the output file (the file stops growing but ffmpeg keeps getting the webm chunks)
  • this can go on like this for several minutes, and then ffmpeg resumes writing to the wav file
  • eventually, the complete wav file is written successfully, but this causes huge delays in the streaming process.

  Looking at CPU and memory usage, this doesn’t seem to be the issue.

  Any ideas as to what could cause ffmpeg to stop streaming for several minutes and then resume ?
  This can happen after 30 seconds, after 3 minutes or after an hour of streaming media chunks and the time it takes ffmpeg to resume also varies.

  In my python code, I’m basically opening a subprocess.Popen() process and write to the process’ stdin to feed ffmpeg the media chunks.

  So my code looks something like :

  ffmpeg_proc = subprocess.Popen('ffmpeg -y -f webm -i - -ac 1 -ar 16000  -f wav /tmp/out.wav', shell=True, stdin=subprocess.PIPE)
  
  
  
  for chunk in chunks:
  
      ffmpeg_proc.stdin.write(chunk)

  I’m using python 3.6 and ffmpeg version 2.8.14-0ubuntu0.16.04.1

  Thanks in advance !