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• ffmpeg - Retrieving video macroblock info with -debug mb_type command

  18 juin 2018, par fabridigua

  I am trying to get the information about all the macroblocks in the frames of a video (mp4).
  In particular i’m using the ffmpeg command :

  ffmpeg -debug mb_type -i input.mp4 out.mp4 2> macroblocks.txt

  It seems to work fine, but... i don’t understand how to parse the output !

  I see that after many uninteresting writings, starts a group of blocks starting with

  "New frame, type : [FRAME TYPE]"

  so I assume that these are the blocks referring to each frame containing the type of each macroblock.. but what do the symbols inside mean ?

  New frame, type : B [h264 @ 000001c0241c1cc0] d < X- < I > > > >
  X d d d d d < < d < d > < d d > d < d d d < > <
  d < > X < d d > d X d < > d X d > > d d+ d

  From the theory I know that there are intra or predicted macroblocks, but i don’t understand how to parse this info from the "New frame"-blocks.

  • What means i,I,A,<,>,X,|,etc.?

  Also often there are sentences like

  nal_unit_type : 1(Coded slice of a non-IDR picture), nal_ref_idc : 2

  or

  cur_dts is invalid (this is harmless if it occurs once at the start
  per stream)

  that i really don’t understand...
  I can’t too find a documentation..
  Can anyone help me ?

• ffmpeg - Retriving video macroblock info with -debug mb_type command

  14 juin 2018, par fabridigua

  I am trying to get the information about all the macroblocks in the frames of a video (mp4).
  In particular i’m using the ffmpeg command :

  ffmpeg -debug mb_type -i input.mp4 out.mp4 2> macroblocks.txt

  It seams to work fine, but... i don’t understand how to parse the output !

  I see that after many uninteresting writings, starts a group of blocks starting with

  "New frame, type : [FRAME TYPE]"

  so I assume that these are the blocks referring to each frame containing the type of each macroblock.. but what mean the symbols inside ?

  New frame, type : B [h264 @ 000001c0241c1cc0] d < X- < I > > > >
  X d d d d d < < d < d > < d d > d < d d d < > <
  d < > X < d d > d X d < > d X d > > d d+ d

  From the theory I know that there are intra or predicted macroblocks, but i don’t understand how parse this info from the "New frame"-blocks.

  • What mean i,I,A,<,>,X,|,etc.?

  Also often there are sentences like

  nal_unit_type : 1(Coded slice of a non-IDR picture), nal_ref_idc : 2

  or

  cur_dts is invalid (this is harmless if it occurs once at the start
  per stream)

  that i really don’t understand...
  I can’t too find a documentation..
  Can anyone help me ?

• How can I extract the metadata and bitrate info from a audio/video file in python

  4 janvier 2015, par Fight Fire With Fire

  What I would like to do is get the metadata from audio or video files and save it to a database record, so far the only way to do this seems to save AVCONV/FFMPEG to a file using a subprocess.Open call then read that file, is there any libraries that can do this to save some steps ? I couldn’t find a way to do it with Pydub or PySox. Here is my simplistic hamfisted beginner code I used that does work and puts the bitrate, duration, etc info into a variable audio_info and the metadata into metadata. OGG output worked differently than the other formats i tested (which was a ton of video and audio !).

      try:
  
              p = subprocess.Popen(["avconv" , "-i" , music_file], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  
              out, err = p.communicate()
  
              retcode = p.wait()
  
      except IOError,e:
  
              pass
  
      extension = uploaded_music_file[-3:]
  
      if "ogg" not in [err , extension]:
  
              if "Metadata:" in err:
  
                      list = err.split("Metadata:")
  
                      holder = list[1].split("Duration:")
  
                      metadata = holder[0]
  
                      audio_info = holder[1].replace("At least one output file must be specified","")
  
                      print metadata
  
                      print audio_info
  
              else:
  
                      list = err.split("Duration:")
  
                      audio_info = list[1].replace("At least one output file must be specified","")
  
                      print "No Metadata"
  
                      print audio_info
  
      else:
  
              list = err.split("Duration:")
  
              if "Metadata:" in list[1]:
  
                      data = list[1].split("Metadata:")
  
                      metadata = data[1].replace("At least one output file must be specified","")
  
                      audio_info = data[0]
  
                      print metadata
  
                      print audio_info
  
              else:
  
                      audio_info = list[1].replace("At least one output file must be specified","")
  
                      print "No Metadata"
  
                      print audio_info
  
  if (audio_info):
  
              print "AUDIO INFO:"
  
              cursor.execute("UPDATE songDB SET audio_info = %s WHERE id = %s" ,[ audio_info , song_id ] )
  
              if (metadata):
  
                      print "METADATA:"
  
                      cursor.execute("songDB pack_song SET metadata = %s WHERE id = %s" ,[ metadata , song_id ] )