DVD-Audio is the now mostly-dead high-resolution audio (and video) format that competed with the also mostly-failed SACD disc format from Sony. DVD-Audio players could play both stereo and 5.1 surround sound discs. They had video output (unlike SACD), as well as backwards compatibility with DVD-Video discs.
DVD-Audio's highest level of audio came via Meridian Lossless Packing (MLP) which was a codec that could reproduce a convincing copy of the master tape mixed in stereo or 5.1 surround. Record labels in their infinite wisdom forced consumers to use 5.1 analog outputs for MLP because of fears of piracy. They should have been fearful that consumers would reject the format because of a lack of quality titles, the $1000 cost of the players, the cost of the eight cables needed and the need for a new surround sound AV preamp. With only a handful or two of top titles ever released on DVD-Audio, consumers in the mainstream rejected the format. It is still available, though entirely as a niche format.
MLP, though, actually lives on. Dolby TrueHD found on Blu-ray is based on MLP, and adds higher bit-rates, more channels, and more.
Certain Blu-ray players, like those from Denon, Marantz, and Oppo, are able to play back DVD-Audio discs.
HomeTheaterReview.com's reviews of DVD-Audio players inlcude:
Rotel RDV-1080 DVD-Audio player
Denon DBP-1611UD Blu-ray player
Oppo BDP-80 Blu-ray player
Oppo BDP-83 Special Edition universal player