Software needed for this step of DVD conversion:

[VStrip Demultiplexer] [GraphEdit Filter Designer]
[Intervideo Dolby Digital (AC3) Decoder]

The best way of decompressing the AC3-stream for later MP3/Vorbis encoding is to use the AC3 Decoder Filter found in the Intervideo WinDVD Package. It offers great quality and is not as low volumed as AC3DEC. But here we go with the tutorial:

• Download GraphEdit and the Intervideo Filter und unzip in appropriate directories.
  
• Register the filters with the corresponding batchfile.
  
• Open a command prompt and change directory to where your VOB-Files are lying.
  
• Use the VSTRIP Tool to demultiplex the audio stream from the VOB.
  (If you copied the whole vob-file structure to harddisk without joining the VOBs refer to the list-file method)
• Use the following commandline to demultiplex the audio stream:
  
  vstrip vts_01_x.vob -!oaudio.vob 0xbe 0xbd 0x8s = 0x80
  
  0x8s is the language you wanna strip. 0x80 is first language, 0x81 is second
  0xbe is the padding stream since the AC3 decoder cannot take plain AC3 Files
  
  
• If you had several VOB-Files then you can use the list-feature of vstrip:
  
  
  • Generate a listfile movie.lst
  • In each line put the name of the next vts_01_x.vob file
    (including full path !!!)
  • Save this file to disk
  • Use the following commandline to demultiplex the audio:
    
    vstrip @movie.lst -!oaudio.vob 0xbe 0xbd 0x8s = 0x80
    
    As above 08xs is the language you want to strip.
    
    
• After doing so fire up GraphEdit and load the enclosed Graph AC3-to-WAV.grf (make sure that your demuxed vob is called c:\audio.vob)
  
  Note:
  If you want to build the filter yourself click on the picture below to get a view on how the filter should look like. You cannot load the .grf file if you don't have all the filters installed.
  
  
  [Click to enlarge]
  
  
• Hit play and when GraphEdit finished you have a file called c:\audio.wav sitting on your harddrive for further processing.

Now you're having one video-stream in the AVI Format and an audio stream in WAV-Format just follow the link to the Remultiplexing Page.