In a previous post I outlined the method I used to rip multichannel surround audio from my DVD-A collection. As was pointed out in the comments, the method works but isn't entirely correct.
As I discovered now, DVD-Audio discs usually contain both Video and Audio data. The audio data, which are the advertised high resolution 24 bit surround tracks, are located in the AUDIO_TS folder. For compatibility reasons (I guess), all DVDs also contain a standard VIDEO_TS folder that contains a normal DVD movie with compressed DTS sound. The video data is great if you want to playback the disc on a home theater (and show off your surround system, perhaps) or to access the bonus features.
But to get the full listening experience it is best to use the uncompressed PCM audio data. Here's an illustrated guide on how to rip the tracks.
Unfortunately, the only problem is that you can't easily bring the music with you: even if you manage to bring the 5.1 headphones, you can't schlep a ton of DVDs even if you wanted. A week ago I finally found out how to rip the DTS audio data on a DVD-A disc to a digital file containing all 6 surround tracks. I'm now enjoying my collection of Porcupine Tree and No-Man records in full 5.1 greatness. 
