iTunes, others mulling move to 24-bit music tracks

Apple and others are considering upgrading the audio on tracks a second time to get close to master-level audio quality, sources both public and otherwise said on Tuesday. Label heads are negotiating to bring the underlying bit depth from 16-bit to 24-bit. The move would bring the audio quality from CD-level to the same detail as the master tracks from the studio,CNN heard, or of the rarely used DVD-Audio format.

Interscope-Geffen-A&M head Jimmy Iovine at the HP webOS event ended up inadvertently if briefly confirming a push towards 24-bit audio through music stores and hinted that Apple and others might have to upgrade the iPhone, iPod and other devices to handle the extra depth.

"We've gone back now at Universal, and we're changing our pipes to 24-bit," he said. "And Apple has been great. We're working with them and other digital services -- download services -- to change to 24-bit. And some of their electronic devices are going to be changed as well."

Existing devices from the industry can handle lossless audio formats like Apple Lossless, AIFF, and FLAC, but they still lose significant detail without the source material having an underlying 24-bit depth. Compressed audio like the AAC or MP3 used on most stores won't necessarily bring out the full 24-bit quality but can still usually see an improvement by giving the audio the most efficient use of the bitrate, or bandwidth, assigned to the format.

The strategy could partly eliminate an audiophile complaint about digital music stores, although many aren't likely to offer the lossless files they would need to get studio-quality tracks. Where most are either pushing the limits of lossy audio with 256Kbps AAC or 320Kbps MP3, lossless usually starts at about 700Kbps and would more than double the file size of songs. The shift would greatly reduce the number of songs that could fit on to an iPhone or a similar device, and might make a MobileMe media locker difficult to use over 3G in some areas.

Audio quality has so far only taken one real leap in online music stores, when most went from selling tracks at a 128Kbps bitrate to at least 256Kbps or 320Kbps. While enough for even intermediate users, those with high-end speakers or studio monitor-level headphones can often notice the lack of detail.