A CLOSER look at DVD-AUDIO

Emedia Professional, June, 1999 by Mark Waldrep

Since my last column, when I asked whether it's time for the record industry and musicians to embrace DVD-Audio, much interest has centered on the new format and the production realities of producing music for release on DVD-Audio in time for Christmas. For one, the issues surrounding copyright protection--both direct digital copying and analog watermarking--are nearing completion and acceptance by the record companies and industry organizations. The "universal" hardware required by the new spec is ready to roll, and musicians seem genuinely curious about the creative and technical potential of DVD-Audio. Plus, many studios and mastering companies have begun creating surround mixes in anticipation of the new format.

At the same time, an ever-increasing number of record companies are finding success in releasing their content in the existing DVD-Video format, complete with 5.1 mixes, interactivity, and concert video footage. In fact, AIX Media Group has recently completed DVD-Video music projects for both Capitol and Rhino Records. These developments beg the following questions, then: In this age of converging media, what are the chances for a separate music-only format, and what are the particulars of the DVD-Audio specification?

in the beginning...

The DVD-Video and Audio specifications were originally slated for completion around the same time. For many reasons--both political and technical--that didn't happen. In the intervening years, the Working Group 4 (WG-4) met regularly and just recently delivered a DVD-Audio spec supported by both the major record and consumer electronic companies. The spec endorses Dolby Digital AC-3 and Meridian Lossless Packing (MLP), but leaves as optional SDDS and DTS.

Sony and Philips, both members of WG-4, heavily promoted their DSD (Direct Streaming Digital) high-resolution digital encoding methodology, but were excluded from the final spec. They've since proposed a competing high-resolution audio-only format known as Super Audio Compact Disc, while remaining active in WG4--which means consumers may have to choose between two new music-only formats at Christmas. And that's in addition to the products that have already been mixed in surround, encoded in Dolby Digital or DTS, and released on DVD-Video and traditional CDs.

The hardware being readied for the consumer marketplace in the fourth quarter will play both DVD-Video and Audio products. These new players, known as "universal" machines, will differ only slightly from existing hardware, featuring additional on-board software to decode the MLP streams and an additional set of output connectors for the six discrete uncompressed audio channels. What's more, automobile manufacturers are prepared to install DVD-Audio and/or universal players in the next generation of SUVs, portable DVD-Audio players are forthcoming, and both Dolby and Sony have announced surround headphones for private listening. Indeed, by this time next year, producing, mixing, mastering, and listening to music through multiple speakers will be commonplace.

deconstructing DVD-A/V

A DVD-Audio disc may be constructed in one of two ways. The first type contains audio only and requires updated hardware. Discs of this type are higher-resolution replacements for the traditional CD-Audio discs distributed by record companies today.

DVD title producers could also opt for a hybrid DVD-Audio/Video (DVD-A/V) disc, which contains a portion laid out in the DVD-Audio spec and a portion using the existing DVD-Video spec. Players of both types could access the audio media, in appropriate formats, on the DVD-A/V disc. For those of us who've already purchased DVD-Video decks, this backward compatibility is especially important. Using nonuniversal equipment, DVD-Video players would be able to access the video portion of the disc and play tracks in Dolby Digital or PCM tracks of up to 96KHz/24-bit. It would not be possible to play MLP tracks or PCM at 192KHz.

DVD-Audio discs could play approximately 75 minutes of full 96KHz/24-bit, 5.1-channel audio encoded using the new MLP algorithm. Higher resolution two-channel PCM tracks at 192KHz/24-bit also could be included, provided the total capacity of the disc wasn't exceeded. For consumers who don't yet have the necessary multichannel playback hardware, the DVD-Audio spec includes a built-in method for down-mixing the multichannel 5.1 mix to stereo. Producers using this option can then determine the placement and level of their tracks as reproduced through two channels. Currently, 5.1-encoded tracks are "folded down" according to the algorithm of the decoder in each individual A/V receiver--a method that is somewhat arbitrary and usually musically unacceptable. Most music releases on DVD-Video include a separate selectable two-channel mix to avoid the automatic fold down.

Using this approach, video would be replaced with a series of still images on DVD-Video-only discs. At the start of each track, a 2MB buffer would be loaded into the player from the disc and would allow the user to control the display by selecting among roughly 20 pictures. The DVD-Audio player provides a variety of fade types between the pictures so you can peruse graphics and liner notes on your TV while listening to tracks.