Just a bit more info. on DTS-HD, from wikipedia:

DTS-HD High Resolution Audio, like DTS-HD Master Audio, is an extension to the original DTS audio format. It delivers up to 7.1 channels of sound at 96 kHz sampling frequency and 24 bit depth resolution. DTS-HD High Resolution Audio is selected as an optional surround sound format for Blu-ray Disc and HD DVD with constant bit rates up to respectively 6.0 Mbit/s and 3.0 Mbit/s. It is supposed to be an alternative for DTS-HD Master Audio where disc space may not allow it.

DTS-HD Master Audio, previously known as DTS++ and DTS-HD, supports a virtually unlimited number of surround sound channels, can downmix to 5.1 and two-channel, and can deliver audio quality at bit rates extending from DTS Digital Surround up to lossless (24-bit, 192 kHz). DTS-HD Master Audio is selected as an optional surround sound format for Blu-ray and HD DVD, where it has been limited to a maximum of 8 discrete channels. DTS-HD MA supports variable bit rates up to 24.5 Mbit/s on a Blu-ray Disc and up to 18.0 Mbit/s for HD-DVD, with 6 channel encoded at up to 192 kHz or 8 channels encoded at 96 kHz/24 bit. In case more than 6 channels are used, a "Channel Remapping" function allows for remixing the soundtrack to compensate for a different channel layout in the playback system compared to the original mix. Currently the Japanese version Pioneer BDP-LX80 supports bitstream digital output of the format along with the Samsung BD-P1400 (through a firmware update). All Blu-ray and HD DVD players can decode the DTS "core" resolution soundtrack at 1.5 Mbit/s, however. DTS-HD Master Audio and Dolby TrueHD are the only technologies that deliver compressed lossless surround sound for these new disc formats, ensuring the highest quality audio performance available in the new standards. (N.B.: DTS Coherent Acoustics coding system has been selected as mandatory audio technology for both the Blu-ray Disc (BD) and High Definition Digital Versatile Disc (HD DVD).[7])