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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 ?

• ffprobe returns mov,mp4,m4a,3gp,3g2,mj2

  19 octobre 2015, par sathia

  I’m trying to find a certain way to understand if a given file is using the h.264 codec and it’s streamable.

  I’m using ffprobe and sometimes I get output such as this :

  {
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'file.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 2036-02-06 06:28:16
  
      encoder         : HandBrake 0.10.2 2015060900
  
    Duration: 00:06:42.13, start: 0.000000, bitrate: 950 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt709), 640x480 [SAR 1:1 DAR 4:3], 788 kb/s, 30 fps, 30 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        creation_time   : 2036-02-06 06:28:16
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 155 kb/s (default)
  
      Metadata:
  
        creation_time   : 2036-02-06 06:28:16
  
        handler_name    : Stereo
  
      "format": {
  
          "filename": "file.mp4",
  
          "nb_streams": 2,
  
          "nb_programs": 0,
  
          "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
  
          "format_long_name": "QuickTime / MOV",
  
          "start_time": "0.000000",
  
          "duration": "402.134000",
  
          "size": "47787790",
  
          "bit_rate": "950683",
  
          "probe_score": 100,
  
          "tags": {
  
              "major_brand": "mp42",
  
              "minor_version": "512",
  
              "compatible_brands": "isomiso2avc1mp41",
  
              "creation_time": "2036-02-06 06:28:16",
  
              "encoder": "HandBrake 0.10.2 2015060900"
  
          }
  
      }
  
  }

  now, it seems that the file is streamable and it’s ok to be put online, but I was expecting something like this :

      "format_name": "h.264",

  instead I get

      "format_name": "mov,mp4,m4a,3gp,3g2,mj2",

  which seems very lax in terms of specifying what the hell this file is.
  I’m also using MP4Box in order to see if the video is streamable, but at this point I’m not sure how to handle specific h.264 recognition.

  what should I do in order to be sure that a given file has the h.264 codec ?

  thanks

• 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.