If a picture’s worth a thousand words, a high-definition movie may be worth, well, a whole lot more. But a good chunk of the praise for HD DVD and Blu-ray Disc high-definition DVD players has to go to the gut-wrenching soundtracks brought to life by next-generation Dolby and DTS surround-sound codecs that reel you in and keep you hooked.

Maybe you thought it didn’t get any better than the 5.1- or 6.1-channel soundtracks we’ve enjoyed with surround-sound encoding by Dolby and DTS. They were the best available for standard DVD. But the extra gigabytes of disc space on a Blu-ray or HD DVD disc not only provide more room for high-def video and cool interactive features but offer discrete 7.1-channel high-def sound, too. You can now for the first time get a bit-for-bit replica of the original soundtrack—without any compression. Here’s a look at the latest surround-sound formats.

Dolby TrueHD is the mandatory format for HD DVD and an optional format for Blu-ray. Dolby TrueHD uses the extra capacity of both formats to offer soundtracks with up to eight channels and that are identical to the studio master. Dolby Digital Plus is the backward-compatible extension to Dolby Digital. Digital Plus uses minimal compression, but its higher data rates deliver more information for improved sound quality over Dolby Digital. Dolby Digital Plus can be used by a studio as a space-saving alternative to Dolby TrueHD for extra-long movies, features such as director commentary and additional languages.

Currently all HD DVD and Blu-ray Disc players decode Dolby TrueHD and Digital Plus internally. You need HDMI 1.3 to pass through Dolby TrueHD in lossless form. Onkyo, for one, recently introduced receivers (ranging in price from $600 to $2,100) that are capable of decoding DTS-HD Master Audio, Dolby TrueHD and Dolby Digital Plus. Disc players with HDMI 1.3 could be out by the end of the year, although most models announced thus far are limited to HDMI 1.2. In the meantime, players will output a high-res PCM signal (CDs are encoded in PCM) that can be played back through an A/V receiver via HDMI 1, 2 or 3 connectors; via 6- or 8-channel analog outputs; or through coaxial or optical audio connections.

A few recommended Dolby TrueHD titles to look for: Superman Returns, Poseidon and Legends of Jazz, a 96-K high-res music video.

Like Dolby TrueHD, DTS-HD Master Audio delivers sound that is bit-for-bit identical to the original. Unlike TrueHD, it is not a mandatory audio format for HD DVD. According to Tom Dixon, director of strategic marketing at DTS, “It is up to the studio to ultimately decide what to include on the discs, but initial response has shown a lot of interest in including DTS-HD Master Audio soundtracks on both HD DVD and Blu-ray Disc content.”

The additional capacity on the high-def discs gives sound engineers more to work with, which allows for richer, full-range audio up to 24.5 Mbps on Blu-ray and 18 Mbps on HD DVD. (Compare that to the 128 kilobits for standard MP3s.)

To get the full lossless benefits of DTS-HD Master Audio, you need a Blu-ray or HD DVD player with an HDMI 1.3 connector, an A/V receiver with HDMI 1.3, and an internal DTS-HD Master Audio decoder. No worries: You can still play back DTS-HD-enabled discs on Blu-ray or HD DVD players using existing receivers with DTS encoders. They’ll res down to 1.5 Mbps, but that’s still twice the data of a standard DVD.

DTS-HD Master Audio titles to look for: Behind Enemy Lines, The Usual Suspects and Pat Metheny’s The Way Up Live.