Apple probably wants HD-AAC for iTunes Match

Yesterday I reported in the Guardian on Apple's plans to upgrade its iTunes Match library to offer "adaptive streaming".The theory is, anything you re-download (or stream?) from iTunes Match will be at the best quality available for your device or connection speed.

HD-AAC is developed by Fraunhofer - the German folk behind AAC, MP3 and a bunch of other smart codecs - and the promotional guide to HD-AAC pretty much spells out the rumours in the Guardian post:

Songs stored on media servers in the HD-AAC format can be streamed to multiple devices at varying bit-rates. This maximizes the sound quality under difficult network conditions by matching the bit-rate to the available bandwidth.

It's a great format too; lossless encoding of 24-bit audio up to 192KHz, a compression ratio of 2:1, and immediately compatible with AAC-enabled devices. That is, the entire Apple line.

This image shows how the iTunes server could store a 24-bit/192KHz file (left), deliver a lossless version to the consumer (middle) and even deliver a lo-res version if your connection speed sucks (right). Seemingly all from one file.

There's no hard evidence Apple will use this. But when it starts asking for 24/96 iTunes masters, and we hear that it is working on an adaptive streaming system, this clearly fits the bill.

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