The Working Group’s selection of AAC came after a number of competing formats were proposed; they included MP3, ATRAC and Microsoft’s WMA. Additional formats, such as Vorbis Ogg for example, were not put forward for consideration.

High Fidelity Review has learnt that AAC was chosen for a number of reasons, a Forum member told us that it was clear from the outset that it was “…sounded much better than the others,” although WMA was not included in the early stages of testing. No details of the subjective (or objective) testing methods were forthcoming, nor any information about the bitrates evaluated. AAC can also deliver multi-channel content.

Another positive factor was that AAC is perceived favourably by the music industry because of its associated copyright protection measures and a history of use by legitimate, paid download organisations such as Apple. Conversely, content providers shudder at the very mention of MP3, it is seen as being the root of all evils where piracy activities are concerned. But as reader Mitchell Burt pointed out to us, AAC itself does not provide any rights management functions; the Apple iTunes implementation via their on-line store uses a proprietary DRM package named FairPlay.

All this begs the question, what (if any) digital rights management system will WG4 choose to partner with AAC for the DVD-ROM zone of DVD-Audio discs?

It could be argued that the choice of AAC will limit consumer acceptance to some degree. While it is true that most portable devices support the format, it barely registers in terms of public awareness, unlike MP3, which has become a buzzword for every teenager and his dog.

The inclusion of a DVD-ROM zone upon a DVD-Audio disc is the choice of the label concerned and is likely to be based upon whether or not they believe the addition will behove the title. In other words, we’re probably going to see lossy content for the likes of music PC and iPod users on a Britney Spears disc, but not as part of the latest freeform jazz title from The Other People.

AAC is not an option however, it is the only approved lossy format and portable players will default to this area of the disc for a number of reasons; it can be replayed with considerably less processing power than the high-resolution content (a welcome side-effect being increased battery life) and the disc only needs to spin at low speeds given that the data throughput required is just a fraction of that demanded by MLP or PCM.

And what of encoders? Once again AAC suffers alongside MP3 and even Vorbis Ogg, for which there are a plethora of end-user solutions. Those behind DVD-Audio don’t see this as a problem however, stating that until there is a consumer authoring package for DVD-Audio discs with ROM zone support the issue is moot. It seems logical that when such a package does become available, it should automatically include an AAC encoder.

Advanced Audio Coding (AAC) was developed by Dolby Laboratories, Fraunhofer, AT&T, Sony and Nokia to provide high-quality audio that compresses more efficiently than earlier formats. Licensing is handled by Via Licensing Corporation, an independent subsidiary of Dolby Laboratories, who also license Meridian Lossless Packing, the compression scheme used for the high-resolution content of most DVD-Audio titles. For more information, visit the link at the foot of this story.

Update 23/03/2004:

We’ve received a couple of messages asking for confirmation of the current status of the DVD Forum’s decision regarding AAC as the chosen format for the ROM zone of DVD-Audio discs, prompted by confusion surrounding meeting minutes and information published upon the DVD Forum’s web site, specifically “Adoption of the mandatory audio codec ‘MPEG-4 HE AAC’ for the Optional Specifications for DVD-Audio (ROM zone)” being listed as “Not Approved”.

There are two parts to format selection, Working Group approval, where a system is chosen based upon its technical suitability and performance attributes, and Steering Committee approval (the next stage) where financial agreements are made in regard to licensing fees, logo usage and the like.