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• Popen.communicate() returns only err when running ffmpeg

  17 février 2013, par Jan Pulpan

  I'm trying to run ffmpeg from python and get some reasonable output. Doesn't matter what ffmpeg's log level is set, the only output I get from Popen.communicate() is err one. The content isn't an error however. I tried the same code to run other commands (ls) and it seems to be Ok with both out and err outputs.

  I checked here and Google and unfortunately found nothing. Most of the examples use os or commands modules, not subprocess.

  This is my test code :

  command = [
  
          'ffmpeg',
  
          '-v', 'debug',
  
          '-i', '1.mov',
  
          '-vcodec', 'libx264',
  
          '-profile:v', 'high',
  
          '-preset', 'slower',
  
          '-b:v', '1000k',
  
          '-vf', 'scale=-1:720',
  
          '-threads', '0', 
  
          '-acodec', 'libfdk_aac',
  
          '-b:a', '192k',
  
          '-y',   
  
          '2.mp4',
  
          ]
  
  p = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  
  out, err =  p.communicate()
  
  f = open('out.log', 'w')
  
  f.write(out)
  
  f.close()
  
  f = open('error.log', 'w')
  
  f.write(err)
  
  f.close()

  Have you ever see something like this ? Am I doing any mistakes or is there an bug in ffmpeg ?

• FFmpeg av_guess_format returns NULL

  12 septembre 2014, par Kage

  I’m following the example code here : http://cekirdek.pardus.org.tr/ ismail/ffmpeg-docs/output-example_8c-source.html

  My code is as follows :

  fmt = av_guess_format(NULL, filename, NULL);
  
  if (!fmt) {
  
          LOGE(1,"Could not deduce output format from file extension: using MPEG.\n");
  
          fmt = av_guess_format("mp4", NULL, NULL);
  
  }
  
      if (!fmt) {
  
          LOGE(1, "Could not find suitable output format\n");
  
          exit(1);
  
  }

  The two times that I call av_guess_format, it is returning NULL both times.
  I am calling both av_register_all() and avcodec_register_all() beforehand.

  Any ideas as to why this is returning NULL ?

  Thanks in advance.

• FFMPEG returns negative values and stops rendering

  15 janvier 2020, par Mike

  While trying to get a 16:9 aspect output from any resolution input, I keep running into errors.

  This is, what I prompt :

  ffmpeg -i "input.mp4" -i "overlay.png" -strict -2 -vcodec h264 -aspect 16:9 -filter_complex "[0]scale=604:-2,pad=604:340:(604-iw)/2:(340-ih)/2[v];[v][1]overlay=x=W-w-5:y=H-h-5" -an "output.mp4"

  Errors are :

  [0] => [Parsed_pad_1 @ 0xeffca0] Negative values are not acceptable.
  
  [1] => [Parsed_pad_1 @ 0xeffca0] Failed to configure input pad on Parsed_pad_1
  
  [2] => Error configuring complex filters.
  
  [3] => Invalid argument

  I’m happy for any help.