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• ffmpeg produced .wav reads only zeros with scipy.io.wavfile

  8 janvier 2015, par question_mark

  Hi everyone and thanks for reading.

  I wanted to do some analysis on a song using Python’s scipy.io.wavfile. Since I only have the song as .mp3 I converted the file to .wav using ffmpeg the following way :

  ffmpeg -i test.mp3 test.wav

  The .wav file plays perfectly well with vlc player, but wavfile shows only zeroes when reading it :

  from scipy.io import wavfile as wf
  
  
  
  data = wf.read("test.wav")
  
  C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.py:42: WavFileWarning: Unknown wave file format
  
    warnings.warn("Unknown wave file format", WavFileWarning)
  
  
  
  data
  
  (44100, array([[0, 0],
  
          [0, 0],
  
          [0, 0],
  
          ..., 
  
          [0, 0],
  
          [0, 0],
  
          [0, 0]], dtype=int16))

  I tried getting the data with Python’s built-in wave module before to the same effect (only zeros).
  I am using the 64bit version of ffmpeg (ffmpeg-20140218-git-61d5970-win64-static).

  Any help is appreciated :-)

  Edit : Included .wav header and tried forcing ffmpeg output format

  I guess the header information of the .wav file is included here :

  ffmpeg -i .\test.wav
  
  Guessed Channel Layout for  Input Stream #0.0 : stereo
  
  Input #0, wav, from '.\test.wav':
  
    Metadata:
  
      artist          : Joe Cocker
  
      copyright       : (C) 1987 Capitol Records, Inc.
  
      date            : 1987
  
      genre           : Pop
  
      title           : Unchain My Heart
  
      album           : Unchain My Heart
  
      track           : 1/10
  
      encoder         : Lavf55.33.100
  
    Duration: 00:05:04.33, bitrate: 1411 kb/s
  
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s

  If I try to specify the ffmpeg output format explicitly for the .mp3 conversion :

  ffmpeg -i .\test.mp3 -f s16le -ar 44100 -ac 2 test.wav
  
  Input #0, mp3, from '.\test.mp3':
  
    Metadata:
  
      title           : Unchain My Heart
  
      artist          : Joe Cocker
  
      album           : Unchain My Heart
  
      genre           : Pop
  
      composer        : Bobby Sharp
  
      track           : 1/10
  
      disc            : 1/1
  
      album_artist    : Joe Cocker
  
      copyright       : (C) 1987 Capitol Records, Inc.
  
      date            : 1987
  
    Duration: 00:05:04.35, start: 0.025056, bitrate: 240 kb/s
  
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 235 kb/s
  
      Stream #0:1: Video: mjpeg, yuvj420p(pc), 600x600 [SAR 1:1 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
  
      Metadata:
  
        title           :
  
        comment         : Cover (front)
  
  Output #0, s16le, to 'test.wav':
  
    Metadata:
  
      title           : Unchain My Heart
  
      artist          : Joe Cocker
  
      album           : Unchain My Heart
  
      genre           : Pop
  
      composer        : Bobby Sharp
  
      track           : 1/10
  
      disc            : 1/1
  
      album_artist    : Joe Cocker
  
      copyright       : (C) 1987 Capitol Records, Inc.
  
      date            : 1987
  
      encoder         : Lavf55.33.100
  
      Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mp3 -> pcm_s16le)
  
  Press [q] to stop, [?] for help
  
  video:0kB audio:52425kB subtitle:0 data:0 global headers:0kB muxing overhead 0.000000%
  
  size=   52425kB time=00:05:04.32 bitrate=1411.2kbits/s

  But in this case (forced format), both ffmpeg and wavfile are not able to read the file :

  ffmpeg -i .\test.wav
  
  .\test.wav: Invalid data found when processing input

  and

  data = wf.read("test2.wav")
  
  ---------------------------------------------------------------------------
  
  ValueError                                Traceback (most recent call last)
  
   in <module>()
  
  ----> 1 data = wf.read("test2.wav")
  
  
  
  C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.pyc in read(filename, mmap)
  
      152 
  
      153     try:
  
  --> 154         fsize = _read_riff_chunk(fid)
  
      155         noc = 1
  
      156         bits = 8
  
  
  
  C:\Program Files\Anaconda\lib\site-packages\scipy\io\wavfile.pyc in _read_riff_chunk(fid)
  
       98         _big_endian = True
  
       99     elif str1 != b'RIFF':
  
  --> 100         raise ValueError("Not a WAV file.")
  
      101     if _big_endian:
  
      102         fmt = '>I'
  
  
  
  ValueError: Not a WAV file.
  
  </module>

• Trolls in trouble

  6 juin 2013, par Mans — Law and liberty

  Life as a patent troll is hopefully set to get more difficult. In a memo describing patent trolls as a “drain on the American economy,” the White House this week outlined a number of steps it is taking to stem this evil tide. Chiming in, the Chief Judge of the Court of Appeals for the Federal Circuit (where patent cases are heard) in a New York Times op-ed laments the toll patent trolling is taking on the industry, and urges judges to use powers already at their disposal to make the practice less attractive. However, while certainly a step in the right direction, these measures all fail to address the more fundamental properties of the patent system allowing trolls to exist in the first place.

  System and method for patent trolling

  Most patent trolling operations comprise the same basic elements :

  1. One or more patents with broad claims.
  2. The patents of (1) acquired by an otherwise non-practising entity (troll).
  3. The entity of (2) filing numerous lawsuits alleging infringement of the patents of (1).
  4. The lawsuits of (3) targeting end users or retailers.
  5. The lawsuits of (3) listing as plaintiffs difficult to trace shell companies.

  The recent legislative actions all take aim at the latter entries in this list. In so doing, they will no doubt cripple the trolls, but the trolls will remain alive, ready to resume their wicked ways once a new loophole is found in the system.

  To kill a patent troll

  As Judge Rader and his co-authors point out in the New York Times, “the problem stems largely from the fact that, [...] trolls have an important strategic advantage over their adversaries : they don’t make anything.” This is the heart of the troll, and this is where the blow should be struck. Our weapon shall be the mightiest judicial sword of all, the Constitution.

  The United States Constitution contains (in Article I, Section 8) the foundation for the patent system (emphasis mine) :

  The Congress shall have Power [...] To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.

  Patent trolls are typically not inventors. They are merely hoarders of other people’s discarded inventions, and that allowing others to reap the benefits of an inventor’s work would somehow promote progress should be a tough argument. Indeed, it is the dissociation between investment and reward which has allowed the patent trolls to rise and prosper.

  In light of the above, the solution to the troll menace is actually strikingly simple : make patents non-transferable.

  Having the inventor retain the rights to his or her inventions (works for hire still being recognised), would render the establishment of non-practising entities, which most trolls are, virtually impossible. The original purpose of patents, to protect the investment of inventors, would remain unaffected, if not strengthened, by such a change.

  Links

  • Taking on Patent Trolls to Protect American Innovation
  • Fact Sheet : White House Task Force on High-Tech Patent Issues
  • Make Patent Trolls Pay in Court
  • Constitution of the United States

• adaptive HTTP streaming for open codecs

  14 octobre 2010, par silvia

  At this week’s FOMS in New York we had one over-arching topic that seemed to be of interest to every single participant : how to do adaptive bitrate streaming over HTTP for open codecs. On the first day, there was a general discussion about the advantages and disadvantages of adaptive HTTP (...)