|Part I: All About The Making of a DVD-Audio Disc|
|Home Theater Feature Articles Audio Related Articles|
|Written by Mark Waldrep, Ph.D.|
|Friday, 01 October 2004|
Page 2 of 3
Planning a DVD-Audio Title: Audio Considerations
The DVD-Audio specification provides a great deal of flexibility to both artists and producers. With flexibility comes choices that need to be made prior to the actual production: recording, mixing, mastering, graphic design and authoring. For a moment, let’s forget about any of the non-musical elements and deal with the choices in the audio arena. As with the DVD-Video specification, the use of Dolby Digital or PCM is common, with DTS often included as an optional format. The number of channels depends on the type of production and the available space on the disc. A typical DVD-Audio disc includes a 5.1 channel Dolby Digital surround mix and a two-channel “stereo” PCM track, both of which can be played on a standard DVD-Video machine – the PCM stereo can even be at 96 kHz/24-bits! These tracks would be placed in the DVD-Video “zone” for complete compatibility with the millions of home theaters in the country. The real benefit of using the DVD-Audio format is its “advanced resolution” capability. By omitting the movie MPEG-2 stream, a 5.1 channel surround mix at 96 kHz/24-bits can be included. At this resolution, it is necessary to use a lossless type of data compression to keep the required data bandwidth within DVD transfer rates. Advanced Resolution DVD-Audio streams are therefore encoded using Meridian Lossless Packing, or MLP. Alternatively, producers can choose to use 48 kHz/24-bits avoiding MLP or even mix and match the sample rates to keep within the bandwidth boundaries, although I’m not aware of a single product or authoring tool that includes this capability.
The options for audio encoding discussed above are employed at the tail end of the production process. Nobody is actually recording their tracks using DTS, Dolby Digital or MLP; these are simply the schemes used on the delivered discs. The other part of the pre-production process involves the particular production path that the audio will undergo on its way to the disc. Remember the days when CDs first appeared and the RIAA designed a coding system to indicate whether a disc was recorded, mixed and mastered in the analog or digital domain? Consumers could read the AAD or DDD designation and have some sense of the production path that was used on the album. Sadly, purchasers of both SACDs and DVD-Audio titles aren’t privy to the type of recording equipment and processing that the audio undergoes prior to encoding. Basically, there are only three choices.