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• WMA Lossless and ProRes Encoder

  4 mars 2012, par Multimedia Mike — General

  The projects (FFmpeg / Libav) just got a WMA lossless decoder. For those keeping score, this means that there are open source methods for decoding every single one of Microsoft’s proprietary audio codecs (Windows Media Audio, or WMA) : WMA v1, WMA v2, WMA9/Pro, WMA Voice, and now WMA lossless. Currently, it’s only advertised to decode 16-bit audio (no 24-bit). Also, when I first tried it a few days ago, it didn’t decode the very end of the single sample file I concocted many years ago (luckynight.wma). But that might be cleared up by now.

  Some other recent developments in the projects that I wanted to call out : An encoder for the Apple ProRes encoder from Kostya ; XWD (X window dump) image decoding and encoding from Paul B. Mahol ; a Sun rasterfile encoder from Aneesh Dogra.

  And then there’s the new playback system for CDXL files, also courtesy of Paul B. Mahol. I wasn’t familiar with this format until I wrote this post, which is surprising, given the format’s vintage. This was a CD-ROM FMV format favored for Amiga computers. Here it is in all its 160x120x10fps glory :

  
  
  

  That’s the amigaball.cdxl sample available in the repository. The sample is 3835910 bytes large and plays for about 24 seconds. This yields a data rate of about 159 kbytes/second. So, yeah, single-speed CD-ROM FMV.

• Theora puts incorrect PTS presentation time on video with held frames

  17 mars 2012, par hexatron

  I have a problem with the packet PTS/DTS on OGG Theora videos with held frames.
  Theora tries to be clever about held frames by omitting duplicate frames
  and using the packet PTS/DTS (they are equal) to skip the held frame time.

  For example, a 2-second-long 10 fps video with frames
  
    A A A A A A A A A A B C D E F G G G G G
  
  should encode with PTS (the frame start) as (note the encoder adds some dup frames)
  
      A 0.0
  
      A 0.1
  
      B 1.0
  
      C 1.1
  
      D 1.2
  
      E 1.3
  
      F 1.4
  
      G 1.5
  
      G 1.9
  
  But libtheora (and ffmpeg) put an incorrect time stamp on frame B
  
  (the first frame following a the dup frames)
  
      B 0.6
  
  This causes video to hiccup on the mislabeled frame.
  
  
  
  My crude fix for this is to use
  
      current frame PTS =  (next frame PTS time) - (one frame time)
  
  and
  
      last frame PTS = duration - (one frame time)

  (I tried submitting a bug report for theora at xiph.org, as the theora site recommends, but could not figure out how to register for a login. I also noticed the reports were several years old, so decided to document this behavior here)

• PHP ffmpeg fetch metadata missing title, author, comment, artist

  19 avril 2012, par chrismacp

  I've been trying to fetch remote mp3 (and other format) meta data using the php5-ffmpeg extension.

  It is working although I am always missing the title, author, comment, artist details.

  I've been scouring the web for an answer but not found any solution.

  I did find this patch http://cvs.pld-linux.org/cgi-bin/viewvc.cgi/cvs/packages/php-ffmpeg/tests-metadata-api.patch which I thought may solve the problem, but I've been unable to compile php-ffmpeg even without the patch so haven't been able to work out if it will fix the problem.

  It seems this extension was abandoned a couple of years ago so I'm not holding out much hope of getting this working.

  Does anyone have any ideas of how to get remote meta data from audio video files using other tools ?

  I am thinking of just parsing the output of ffmpeg itelf using the '-i' option as this does return the correct meta data. Just a bit wary of calling exec in PHP for security reasons.