Apple Is Secretly Upgrading Your iTunes Library

By Tom Davenport on at

Last year we argued that 24-bit audio on iTunes would be a consumer con. We were right, of course -- albums don't need the same dynamic range as a jet engine to be enjoyable, no matter what those audiophile chumps will have you believe. But now Apple's HD audio plans are becoming clearer, and we're actually blown away with what it might offer. If the latest rumours are true, it will solve our complaints about file sizes and still cater to folk with premium speakers. Everyone wins.

As reported in the Guardian, Apple is looking to upgrade iTunes to offer an "adaptive streaming" format. The theory is that iTunes Match will function as usual, but instead of storing 256kbps files in iCloud it will keep HD versions at 24-bit/96KHz.

First, let's put those weird numbers in context. A 256kbps AAC song is a regular iTunes audio file. Only a few MB, and it sounds okay, though you wouldn't pay for anything less.

A so-called HD file (like 24-bit/96KHz) is the opposite; ultra-high resolution and technically flawless. When a 3 minute song weighs over 100MB, it's not an option for iOS devices.

Apple's rumoured solution is to keep an HD version on iTunes, from which its users can stream or download smaller versions based on their connection speed.

This means portable streaming to your iPhone without eating your entire monthly internet cap, but could also stream through broadband to your hi-fi or Apple TV in high-fidelity. Touché.

Does Apple have to invent a new file format to make it work? No, because it already exists.

Enter HD-AAC. It allows lossless encoding, compresses to half its original file size, and works with AAC-enabled devices right out of the box. Like, you know, every Apple product.

HD-AAC was developed by the German geniuses at Fraunhofer who invented the MP3 and a bunch of other audio codecs. This image from the spec page shows how the iTunes server could store an HD file (left), deliver a lossless version to the consumer (middle) and even stream a lo-res version when your connection speed sucks (right).

All of this would happen on Apple's server without you changing a single setting -- it just needs the music industry to upload master versions at 24-bit/96KHz. Which is exactly what Apple started doing with its 'Mastered for iTunes' program.

The 'Mastered for iTunes' guidelines explain how studio engineers should prepare music for the great iTunes library in the sky. Apple recognises its iTunes catalog as an important historical and cultural record, and says it wants to future-proof itself with a pristine catalogue, but goes on to accidentally describe how it could support iOS devices:

"Keeping the highest quality masters available in our systems allows for full advantage of future improvements to your music," it says. "These masters matter — especially given the move into the cloud on post-PC devices."

The guide says Apple reviews each submission to ensure there is "a discernible improvement" above previous versions of the same music, though mastering engineer Ian Shepherd has already proven that some music wearing the 'Mastered for iTunes' badge remains unchanged.

"If engineers make special 'Mastered for iTunes' versions that have more dynamics and punch than the CD versions, then the iTunes versions could actually sound better," Ian tells us. "Sadly we haven't seen that yet."

Ultimately, HD-AAC in iTunes Match could prove to be the pinnacle of digital audio. Online video has long adapted to our connection speeds, but audio didn't have a mainstream company backing the concept until now -- and in HD to boot. Good luck to Spotify in competing with that.

HD-AAC. One format to rule them all. And finally, a streaming option to keep those pesky audiophiles quiet.