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• libfdk-aac : Relicense the library wrappers to the ISC license

  6 juin 2014, par Martin Storsjö

  libfdk-aac : Relicense the library wrappers to the ISC license
  This reduces the number of different licenses used within libav,
  
  and is preferrable since it has less ambiguous wordings than
  
  the BSD license with respect to the duties of the user of the code.
  Fraunhofer have now indicated that they’re allowed to contribute
  
  code under this license as well.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/libfdk-aacdec.c
  • [DBH] libavcodec/libfdk-aacenc.c

• mov : Export geotag metadata fields

  3 juin 2014, par Martin Storsjö

  mov : Export geotag metadata fields
  The ’ ?xyz’ form is used by android devices (and according to apple
  
  mailing list archives, also by older iOS devices). The ’loci’ field
  
  (defined in 3GPP 26.244) is used by recent iOS devices.
  Even though the loci field can contain an altitude, it was plain
  
  0 in my sample. Just export longitude and latitude, in a string
  
  format matching the one used by the ’ ?xyz’ metadata field.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/mov.c

• Brute Force Dimensional Analysis

  15 juillet 2010, par Multimedia Mike — Game Hacking, Python

  I was poking at the data files of a really bad (is there any other kind ?) interactive movie video game known simply by one letter : D. The Sega Saturn version of the game is comprised primarily of Sega FILM/CPK files, about which I wrote the book. The second most prolific file type bears the extension ’.dg2’. Cursory examination of sample files revealed an apparently headerless format. Many of the video files are 288x144 in resolution. Multiplying that width by that height and then doubling it (as in, 2 bytes/pixel) yields 82944, which happens to be the size of a number of these DG2 files. Now, if only I had a tool that could take a suspected raw RGB file and convert it to a more standard image format.

  Here’s the FFmpeg conversion recipe I used :

   ffmpeg -f rawvideo -pix_fmt rgb555 -s 288x144 -i raw_file -y output.png
  

  So that covers the files that are suspected to be 288x144 in dimension. But what about other file sizes ? My brute force approach was to try all possible dimensions that would yield a particular file size. The Python code for performing this operation is listed at the end of this post.

  It’s interesting to view the progression as the script compresses to different sizes :

  
  
  

  That ’D’ is supposed to be red. So right away, we see that rgb555(le) is not the correct input format. Annoyingly, FFmpeg cannot handle rgb555be as a raw input format. But this little project worked well enough as a proof of concept.

  If you want to toy around with these files (and I know you do), I have uploaded a selection at : http://multimedia.cx/dg2/.

  Here is my quick Python script for converting one of these files to every acceptable resolution.

  work-out-resolution.py :
  

  PLAIN TEXT

  PYTHON :

  1. # !/usr/bin/python
  2.  
  3. import commands
  4. import math
  5. import os
  6. import sys
  7.  
  8. FFMPEG = "/path/to/ffmpeg"
  9.  
  10. def convert_file(width, height, filename) :
  11.  outfile = "%s-%dx%d.png" % (filename, width, height)
  12.  command = "%s -f rawvideo -pix_fmt rgb555 -s %dx%d -i %s -y %s" % (FFMPEG, width, height, filename, outfile)
  13.  commands.getstatusoutput(command)
  14.  
  15. if len(sys.argv) <2 :
  16.  print "USAGE : work-out-resolution.py <file>"
  17.  sys.exit(1)
  18.  
  19. filename = sys.argv[1]
  20. if not os.path.exists(filename) :
  21.  print filename + " does not exist"
  22.  sys.exit(1)
  23.  
  24. filesize = os.path.getsize(filename) / 2
  25.  
  26. limit = int(math.sqrt(filesize)) + 1
  27. for i in xrange(1, limit) :
  28.  if filesize % i == 0 and filesize & 1 == 0 :
  29.   convert_file(i, filesize / i, filename)
  30.   convert_file(filesize / i, i, filename)