Music Week: Details of New AAC Format and Digital Rights Management

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Date: Wednesday, April 30th, 2003, 07:32
Category: Archive


This is a topic we’ll be following closely through the coming weeks, but the first details are emerging of Apple’s new AAC file format used in iTunes 4 and the iTunes Music Store, and what it means for Digital Rights Management (DRM) and copy protection.

AAC, Advanced Audio Coding, is part of the MPEG4 specification, so what you’re getting is the latest in audio compression technology plus digital rights management to prevent the kind of rampant filesharing that took place with MP3 and the non-copy-protected CD audio format it depends on. Anecdotally, everyone is raving about AAC audio quality, which is difficult to distinguish from the uncompressed audio on an audio CD.

Audio CDs should still sound significantly better to sensitive ears; AAC is itself closer to high-bitrate MP3s. See Apple’s own comparison. Certainly, the audio quality is good enough that few would complain — or even miss their CDs if you rip from CD to AAC. PhatAudio compares AAC, MP3, and OGG; you can finally get at the article — it was seriously Slashdotted yesterday. The article is extensively discussed by the folks on Slashdot.

The big discussion has been Digital Rights Management. The DRM restrictions in AAC are detailed in KB Doc 93025. Only AAC files downloaded from Apple will play, and if you stream AAC files, your listener’s iTunes copy will skip over AAC files it doesn’t own. The last part of that is the most troubling: what if musicians want to take advantage of the AAC audio codecs, but without DRM, say to release a demo track on their own? iTunes won’t play it. The way around may be to release the track as an MP4; there’s just not adequate detail on what QuickTime 6.2 will support. Presumably if it is a QuickTime-supported format, iTunes will play it. The ability to share our own music is critical to those of us making music, so I’ll be covering this topic more in detail (if you know anything, do share!).

The hottest topic on the Web has been deauthorizing, which is covered in Knowledge Base 93014. Authorization is linked to your Apple ID. What’s unclear is what you do if your HD crashes, since that would NOT deauthorize your system. There is unlimited CD burning, but a single playlist can only be burned ten times (see KB 93016) — hardly an unreasonable restriction. MacRumors has some additional analysis of the DRM in AAC.

More tidbits: interrupted downloads will restart when you relaunch iTunes without any additional fee, and iTunes can display your purchase history.

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