Apple is reportedly planning to offer 24-bit audio files for download on its iTunes online music store, complementing or possibly replacing the 16-bit audio files currently available. A CNN report claims that major music labels are in discussions with Apple to offer the higher quality audio files for purchase.
24-bit audio is theoretically superior to the compressed 16-bit, 256KBps AAC audio currently ubiquitous on the iTunes Music store; it is able to contain a wider range of audio frequencies than 16-bit, and most professional audio recording equipment operates natively in 24-bit. Releasing audio in a 24-bit format on iTunes would preserve the same sound quality as a studio recording, allowing iTunes users with high quality equipment access to uncompromised and uncompressed music recordings of their favourite artists.
However, the advantages of 24-bit audio are generally not important to the majority of music listeners — the wider theoretical frequency range and audio nuances can only be faithfully reproduced by high-end stereos and headphones. For example, Apple's bundled earbud headphones are only able to accurately reproduce sounds within the 20Hz-20,000Hz range that the 16-bit audio format already covers. The AAC audio format currently used on the Apple online store is also only a 16-bit codec, so the premium quality files would need to use a high quality codec such as Apple Lossless — which supports 24-bit encoding at high sample rates, but results in large file sizes.
It's likely that Apple's higher quality audio files would also attract a price premium over their compressed counterparts. According to analysis done by the MacStories Web site, Australian iTunes users already pay 69% more than US users for the same content.