When Apple started pushing its “Mastered for iTunes” section of albums “specially tuned for higher fidelity sound,” it also published a white paper detailing new guidelines asking publishers to submit high-resolution 24-bit/96kHz files instead of the original CD masters for inclusion in the section. Many were under the impression that the 100 or so albums in the new section are sonically closer to the original CD source in comparison to your average AAC encode from iTunes. According to British mastering engineer Ian Shepherd, “null testing” proves that is simply not true. In fact, he proves a “vanilla” iTunes AAC encoding with default settings sounds closer to the original CD than songs that were specifically “Mastered for iTunes.” Shepherd explained:
the fact that the new Apple encoders can correctly handle high sample rates, and should make a better job on the conversion, STILL doesn’t mean that the files will sound ‘closer to CD’… In fact, since at the end of the day we’re still getting a lossy encode, it’s my opinion that the advantages of higher bit-depths and sample rates will be completely outweighed by the AAC encoding.
Make no mistake; Shepherd does not have a problem with Apple’s guidelines for engineers submitting 24-bit/96kHz files for Mastered for iTunes. In fact, he said, “People may well prefer the “Mastered for iTunes” versions, and there is absolutely no reason not to make a specific master for a particular release format.” However, the point is the master you are getting from Mastered for iTunes, at least in Shepherd’s tests, sounds different from the original CD versions. The test proves the best way to get an iTunes AAC encode that sounds closest to the CD is to simply buy the CD, and then rip it in iTunes.
Shepherd ended his post by urging Apple to offer a “lossless format” if it really cares about high-quality audio. Today reports from The Guardian suggested Apple was working to deliver a new high-definition audio format, while in the white paper for Mastered for iTunes Apple claimed, “Keeping the highest quality masters available in our systems allows for full advantage of future improvements to your music.”