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• Evolution #3962 : Générer des JPEG progressifs

  18 juin 2017, par Michel Bystranowski

  Mmm, ça a l’air un peu plus compliqué qu’au premier abord effectivement. J’ai trouvé cet article qui compare le taux de compression et recommande de ne le faire que pour les fichiers de plus de 10k, sous peine d’obtenir des fichiers plus gros (https://yuiblog.com/blog/2008/12/05/imageopt-4/). Du coup il faudrait s’arranger pour ne cibler que les gros JPEGs.

  Par côté compatibilité des navigateurs ça semble ok pour tous les navigateurs récents (https://en.wikipedia.org/wiki/Comparison_of_layout_engines_%28graphics%29#JPEG_support).

• What H.264 encoding profile is considered "safe" in 2017 ?

  12 avril 2017, par degenerate

  Have streaming services adopted a certain H.264 profile as "standard" or "safe" for use in 2017 ? For example are all modern Youtube videos at least "High" profile for H.264 ?

  Or does Youtube continue to serve all encoding profiles, down to "Baseline" depending on hardware ?

  I would like to start encoding my videos with "High" profile or higher, but cannot find any recent documentation on which profile is standard practice or safe to use.

  Searching google is not fruitful :

  Old blog post from 2008 :
  http://blog.mediacoderhq.com/h264-profiles-and-levels/

  Old blog post from 2014 :
  http://leightronix.com/blog/when-to-choose-high-main-and-baseline-while-encoding-h-264/

  I cannot find any updated 2017 information on this.

• Trying to convert an mp3 file to a Numpy Array, and ffmpeg just hangs

  5 juillet 2016, par Rich

  I’m working on a music classification methodology with Scikit-learn, and the first step in that process is converting a music file to a numpy array.

  After unsuccessfully trying to call ffmpeg from a python script, I decided to simply pipe the file in directly :

  FFMPEG_BIN = "ffmpeg"
  
  cwd = (os.getcwd())
  
  dcwd = (cwd + "/temp")
  
  if not os.path.exists(dcwd): os.makedirs(dcwd)
  
  
  
  folder_path = sys.argv[1]
  
  f = open("test.txt","a")
  
  
  
  for f in glob.glob(os.path.join(folder_path, "*.mp3")):
  
      ff = f.replace("./", "/")
  
      print("Name: " + ff)
  
      aa = (cwd + ff)
  
  
  
      command = [ FFMPEG_BIN,
  
          '-i',  aa,
  
          '-f', 's16le',
  
          '-acodec', 'pcm_s16le',
  
          '-ar', '22000', # ouput will have 44100 Hz
  
          '-ac', '1', # stereo (set to '1' for mono)
  
          '-']
  
  
  
      pipe = sp.Popen(command, stdout=sp.PIPE, bufsize=10**8)
  
      raw_audio = pipe.proc.stdout.read(88200*4)
  
      audio_array = numpy.fromstring(raw_audio, dtype="int16")
  
      print (str(audio_array))
  
      f.write(audio_array + "\n")

  The problem is, when I run the file, it starts ffmpeg and then does nothing :

  [mp3 @ 0x1446540] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mp3, from '/home/don/Code/Projects/MC/Music/Spaz.mp3':
  
    Metadata:
  
      title           : Spaz
  
      album           : Seeing souns
  
      artist          : N*E*R*D
  
      genre           : Hip-Hop
  
      encoder         : Audiograbber 1.83.01, LAME dll 3.96, 320 Kbit/s, Joint Stereo, Normal quality
  
      track           : 5/12
  
      date            : 2008
  
    Duration: 00:03:50.58, start: 0.000000, bitrate: 320 kb/s
  
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 320 kb/s
  
  Output #0, s16le, to 'pipe:':
  
    Metadata:
  
      title           : Spaz
  
      album           : Seeing souns
  
      artist          : N*E*R*D
  
      genre           : Hip-Hop
  
      date            : 2008
  
      track           : 5/12
  
      encoder         : Lavf56.4.101
  
      Stream #0:0: Audio: pcm_s16le, 22000 Hz, mono, s16, 352 kb/s
  
      Metadata:
  
        encoder         : Lavc56.1.100 pcm_s16le
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mp3 (native) -> pcm_s16le (native))
  
  Press [q] to stop, [?] for help

  It just sits there, hanging, for far longer than the song is. What am I doing wrong here ?,