Detailed information on the DVD-Audio specification is hard to find, but here are some useful introductions:
There are numerous reference books on Digital audio signal processing. An excellent (though costly) introduction to all aspects of audio signal coding, including DVD-Audio and SACD, is to be found in:
Reference: A. Spanias and alii, Chapter 11 "Lossless Audio Coding and Digital Watermarking", Feb 2007, Wiley. The chapter can also be downloaded on a pay-per-view basis from the editor's site.
The DVD-Video and DVD-Audio specifications are very closely linked and the DVD-Video specification is now very well understood and unofficially documented. These links are invaluable when investigating the DVD-Audio specification.