April 2002

What the Heck is DVD-Audio?

You have probably heard of DVD-Audio (DVD-A) and you may even own a player that is capable of playing DVD-A discs, but very few people have actually heard any music played back using this new format, let alone own any of the relatively few titles that are available.

DVD-A is an extension of the DVD format similar to what S-VHS is to VHS. What we think of as the standard DVD format is now sometimes referred to as DVD-V or DVD-Video. DVD-Audio, as the name implies, is primarily an audio-only format. DVD-A discs can contain still pictures and often include menus to navigate through the various tracks on the discs. They may even have limited video footage. However, because the high-resolution audio tracks take up so much of the storage capacity of the disc, there is little room left to store much, if any, high-quality video material. This is why there are no movies on DVD that have DVD-A soundtracks.

What is MLP?

At the heart of the DVD-A format is something called Meridian Lossless Packing (MLP), which is a method of storing multichannel sound not completely unlike Dolby Digital or DTS. However, unlike Dolby Digital or DTS, which are "lossy" compression schemes (meaning they discard some audio data), MLP is a "lossless" method that does not discard any audio data during the encoding and decoding processes. So, you get all the music.

MLP is also much higher in resolution than either Dolby Digital or DTS and can store approximately two hours of two-channel 24-bit/192kHz audio, or six channels of 24-bit/96kHz audio, all on one DVD. Note that both of these configurations are also higher in resolution than the 16-bit word length and 44.1kHz sampling frequency of stereo CDs. Although these are the maximum word lengths and sampling frequencies allowed by the DVD-A specification, lower sampling frequencies, shorter word lengths, and even differing numbers of channels can be utilized.

Hardware compatibility

Because DVD-A is a variant of the standard DVD format, DVD-A players function just like any other DVD player and will play standard DVDs and CDs. Depending on the particular make and model, most DVD-A players can also play CD-Rs and CD-RWs and sometimes even VCDs (Video CDs), MP3-encoded CDs, and most recently DVD-Rs and DVD-RWs. Most DVD-A-capable players are nearly indistinguishable from their standard DVD-V counterparts both in terms of appearance and functionality. In fact, you may own a DVD-A-capable player and not even know it!

How many cables do I need?!!!

DVD-A players will only output their multichannel DVD-A tracks via their analog outputs (with a few exceptions, noted below). Because of copyright infringement issues, the high-resolution multichannel digital signal is not output by the DVD-A player. This was a specification meant to deter digital copying. Thus, unlike Dolby Digital and DTS, you cannot use a single digital cable and rely on your receiver or processor to decode the DVD-A signal. Instead, you must rely on the DVD-A player’s internal decoding and use six RCA-type cables to connect the DVD-A player to the six-channel analog inputs of your receiver or processor.

Note that the six-channel analog inputs of most processors and receivers are direct inputs, meaning that they bypass and disable such DSP-based features as bass management and channel delays.

There are currently a few DVD-A players that will output a proprietary digital signal that can be accepted by a compatible processor or receiver (from the same company), which will perform the necessary decoding, bass management, and channel delays, which would normally be performed inside the DVD-A player. The non-standard, proprietary nature of these digital connections makes them of little use to those trying to make digital copies because they cannot be recorded onto any standard digital format. Currently both Denon and Meridian offer DVD-A players with proprietary digital outputs and compatible receivers and processors, while Pioneer has demonstrated this technology in prototype form.

Software compatibility

Although it is a safe bet that a DVD-A player will be able to play just about any DVD or CD, a DVD-A disc may or may not play back in a standard DVD-V player, depending on how it has been recorded. Although it is not a requirement, many DVD-A discs include optional Dolby Digital and DTS audio tracks that make them compatible with standard DVD-V players. Otherwise a DVD-A disc will only be compatible with a DVD-A-capable player. DVD-A discs (and DVD-V discs for that matter) are not playable on CD players, laserdisc players, or any other optical-disc player that was not specifically designed to play them.

The Toy Matinee DVD-Audio disc features both DTS 5.1 and Dolby Digital 2.0 audio tracks in addition to the DVD-A tracks, making it playable on DVD-V players.

One curious operational quirk of DVD-A players (which is actually part of the DVD-A specification) is that they will automatically default to the DVD-A tracks of a DVD-A disc and will not recognize any other audio tracks such as Dolby Digital and DTS even if they are present. Thus, the optional audio tracks (Dolby Digital or DTS) on DVD-A discs will be invisible to DVD-A players and can only be played back on standard DVD-V players.

So what does the future hold for DVD-Audio?

It is still early in the game, so to speak, so I would not necessarily rush out and purchase a DVD-A player just for the sake of having one. Although the prices of some of these players have dropped to the point where they often do not cost much more than comparable standard DVD-V players, there is still the relative lack of software availability.

If, though, you are contemplating the purchase of a DVD player, you might want to consider purchasing a model with DVD-Audio compatibility, especially if it is available for only a small premium over that of a similar DVD-V player.

While many of the major record labels have announced their support for the DVD-Audio format, they have been slow to release a substantial number of titles. Judging by the large number of software providers and hardware manufacturers that are now supporting the DVD-Audio format, it will no doubt establish itself at least as a niche product among audiophiles for the delivery of high-resolution multichannel music.

Whether it catches on with the general public and becomes a widely accepted format is another matter which only time will tell.

...Roger Kanno
roger@hometheatersound.com

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