While DVD-Audio has already been standardised, it had originally been designed such that its high-fidelity audio could not be easily decrypted in a PC like what happened with DVD-Video. This also meant that it required a dedicated DVD-Audio player to play the high fidelity audio. One way to allow legacy playback with existing DVD-Player's and PCs has been to include either a Dolby digital or DTS DVD-ROM 'zone'. One problem with the current age of music is that Dolby Digital and DTS are not compatible with portable audio players.
To overcome this compatibility issue, the Forum had tried out various audio codec's commonly used by digital audio players including AAC, Windows Media 9, MP3 and Sony's ATRAC codec. AAC as used by iTunes had been chosen due to 'sounding better' than the rest despite the forum choosing WM9 for its HD-DVD format. The AAC tracks will be stored in the DVD-ROM session of the disc for readability in DVD-ROM drives. The AAC codec has also been chosen for its multi-channel capabilities, been easily protected with DRM and also part of the MPEG 4 specification.
According to an unnamed Forum member cited by web site High Fidelity Review, AAC beat Microsoft's Windows Media 9 format, MP3 and Sony's ATRAC because it "sounded better than the others". Ironically, the Forum recently selected Windows Media as the basis for its future high-definition video DVD format. First launched in the late 1990s, DVD Audio is being pitched as a successor to the CD. Sony and Philips are similarly promoting their own next-generation audio format, Super Audio CD (SACD). Keen to avoid the freedom the CD format has granted to PC users to rip tracks to compressed audio formats, DVD Audio was always intended to feature copy protection, though initial versions of the specification lack this 'feature' in order to allow manufacturers to bring players to market. In order to ensure DVD Audio playback on personal computers, the DVD Forum has proposed the inclusion of a DVD-ROM 'zone' on each DVD Audio disc, which the PC-based player will read in preference to the main audio area. That DVD-ROM will hold compressed versions of the songs encoded in DVD Audio format, and its for these compressed tracks that AAC has now been chosen. In addition to its superior sound quality, the format was selected for its support for both multi-channel audio and DRM. Apple uses the latter to protect tracks bought from ITMS. AAC doesn't inherently feature DRM, but its file structure was devised to allow the addition of DRM-related control data. Just as DRM is optional within the AAC file, so too is the DVD-ROM zone within the DVD Audio disc. However, the fact that it is there as a choice for music labels to use should encourage more portable music player makers to build AAC support into their devices as Apple has with its iPod. AAC is also part of the MPEG 4 specification. |
When Apple launched its music store, it was nice to see them choose the superior AAC codec for its music library. Unfortunately this also meant that its music could only be placed back on the iPod range of players. If more DAP manufacturers decide to include AAC support in their products, it will be interesting to see if Apple will allow its music to be placed on other AAC compatible devices also. Unfortunately as Apple rely on iPod sales for profit and not its profitless iTunes sales, it is unlikely Apple will allow iTunes music playback on third party products anytime soon.
Fee free to discuss and read more about DVD-Audio and audio codec's on our Audio Forum.
Source: The Register
