It makes sense. As most listeners will check out a new album on iTunes—or at least the first single from a long-awaited I’m With You release—the Red Hot Chili Peppers and producer Rick Rubin opted to provide the album in three different formats: iTunes’ AAC, CD and vinyl. While creating three different versions from the final mixes may not seem too daunting, for mastering engineer Vlado Meller (pictured), pinpointing the most current AAC encoder proved tricky.
“For iTunes, we take a 44.1k/24-bit file and test it with Apple’s proprietary AAC converter,” Meller explains from his home base in New York City’s Masterdisk. “Apple keeps changing the AAC encoder, and you have to have Apple’s cooperation to make sure you’re hearing the exact results. Until now, we had to guess about what the actual Apple AAC encoder sounded like. The emulations available as plug-ins are only an estimate. Apple’s encoder has evolved and they haven’t provided much information about it in the past. We then tweaked our master so that when the AAC file is played back, it sounds to the ear to be very consistent with the CD.”
Working on his custom mastering hardware, Meller’s purpose-built high-resolution processors allow him to be precise and transparent, making adjustments to EQ and level to help disguise the data reduction in the iTunes version, working closely with mix engineers Andrew Scheps and Greg Fidelman. For the CD version, Meller took Rubin’s 96/24 files, using digital processing to fine-tune each mix and bring it down to 44.1/16. The vinyl master was cut from the original 96/24 mixes.
“I do think this will be a process that every major project will start to consider,” Meller says. “Considering how many listeners are only going to hear the iTunes version, care should be taken to make sure the AAC version sounds as good as it possibly can. As bandwidth and technology improve, so too will the sound quality of streaming and downloaded music. For now, we try to make our existing formats sound as good as they can.”