DVD-Audio Offers Flexibility and Confusion
Gene Radzik, a Dolby audio application engineer for music and broadcast applications, brought a group of journalists and Audio Engineering Society members up to date on both the history and the state of the DVD-Audio art. The easygoing and well-spoken Radzik demonstrated an encyclopedic knowledge of the history of audio in a guided tour of the subject that took us from Edison's tin cylinders to high-bit-rate multichannel recording in a few minutes, and devoted the bulk of his more-than-two-hour discourse to the technical aspects of DVD-A.
After several fits and starts, most of them the result of copyright concerns, DVD-Audio players are finally going on the market worldwide. Among the benefits the format will offer artists and music-lovers are: an unprecedented number of ultra-hi-fi channels; specifications for single-sided, single-layered DVD-A discs citing total data storage of 4.7Gigabytes of information, including six discrete channels with a frequency response of DC–96kHz; a data rate of 9.6Mbps (megabits/second); resolution levels of 16, 20, or 24 bits; and sample rates of 44.1, 48, 88.2, 96, 176.4, and 192kHz. (44.1kHz is the consumer audio sampling-rate standard; 48kHz is the pro-audio equivalent. The higher rates are even multiples of the basic rates.)
Those amazing specifications are only for single-sided, single-layered discs, also known as DVD-5. The format's guiding principles also make room for an 8.5GB single-sided, dual-layered disc called DVD-9. Two-sided, single-layered discs, designated DVD-10, will offer 9.4GB of storage, and DVD-18, the two-sided, two-layered variety, will present a whopping 17GB of storage, using Meridian Lossless Packing (MLP) technology.
Playing time for 24-bit/96kHz six-channel discs will be approximately 89 minutes; 5.1-channel will play for 106 minutes; a 24/96 two-channel disc will play for 230 minutes, and a 24/192 two-channel recording will go 125 minutes. Ordinary CDs, by comparison, offer only 650MB of storage, and only two channels of audio at 16-bit resolution, for an approximate maximum of 74 minutes of music. Engineers are free to use as many or as few channels of DVD-A potential as they wish. Some recordings may need only the front three channels of a multichannel system, for example; others may use only the front and rear pairs.
"Real estate" allocations on a DVD-A disc include a "video zone" and a "graphics menu," in addition to the "audio zone." The size of these zones can be varied according to artists' and producers' intentions, Radzik stated. The audio zone will support six channels of 24/96 digital audio, or two channels at 192kHz. The video zone can be used for browsable still pictures to accompany the music tracks—a feature some call a "slide show." Text information such as lyrics, credits, and links to websites will go in the graphics menu. Video specifications for the format are the same as for DVD-Video discs, except that there is no provision for multi-story options, region controls, or parental management. The audio tracks can exist without video, Radzik mentioned, as may be preferable for DVD music discs intended for portable players.
The DVD-A "audio image" will output compatible signals for 5.1 and Dolby Pro Logic decoders, Radzik said, as well as a stereo "downmix" for two-channel systems or headphone listening. Some engineers have raised issues about the methodology by which natively multichannel recordings can be reduced to two-channel. They have specifically questioned the downmix coefficients, Radzik said. One exceptionally useful feature of DVD-A is a provision for a user-adjustable dynamic-range control that would enable late-night listening without the danger of angering neighbors or family members.
Alongside DVD-V and DVD-A will be a "gray area" format called DVD-AudioV, which will offer DVD-V video quality but not the ultra-hi-rez audio of DVD-A. DVD-AudioV discs will be playable in so-called "combination" players or in DVD-V machines, but not in DVD-A machines. Most DVD players now on the market will not accommodate the new audio formats, and we may see a proliferation of players capable of playing two of the three formats, but not all. They will, however, all play "legacy" CDs (as will SACD players), so the libraries of music lovers are not in danger of immediate obsolescence.
Radzik agreed with a comment from the audience that the budding format offers enormous potential for confusion on the part of consumers. "A $200 universal player would go a long way toward ensuring full market penetration for DVD-A," remarked another attendee. When asked about Dolby's position on Sony's Super Audio CD format, Radzik said simply, "DVD-A is about future growth, not legacy support," a reference to Sony Music's huge catalog, most of which might be remastered in the SACD format if Sony's format gathers sufficient market momentum.
In an e-mail late Thursday, Radzik mentioned that the specifications for DVD-A watermarking and copy protection have been updated. The complete spec can be seen here.