Once the final AAC audio file is generated, the intermediary CAF is deleted. Next, it uses this newly-rendered CAF to render a high-quality AAC audio file. If the sample rate of the source file is greater than 44.1 kHz, it’s downsampled to 44.1 kHz using our mastering-quality SRC. The Droplet creates an AAC audio file from an AIFF or WAVE source file by first generating a CAF (Core Audio File) rendered with an iTunes sound check profile applied to the file. So what changes does the Master for iTunes droplet make to your files? Well, none: it just encodes them. Generally, this difference is in perceived overall volume, but also can include changes to dynamics and other touches. The most important question, though, is how does it sound? If you send a song to be mastered, you expect in general to get back a song that sounds different than the one with which you started. Greater resolution and bit depth are limited to the mastered files, not to what the listener ultimately hears. It still begs the question: why go down to CD specifications, especially while making the point of noting their process results in a quality better than CD’s or CD rips? Ed.: The greater bit-depth is only an intermediary file eventually delivery is not only compressed, but at specifications set by the CD. Most pro audio editors can achieve the same, but often people are ripping MP3s or AACs in their media players, so it is an important distinction. PK Apple’s tools aren’t the only way to do this. According to Apple, their use of greater bit depth in the intermediary file prevents aliasing and clipping, and thus they don’t need to use dithering. Ed.: “Dithering” is the addition of adding small amounts of noise to compensate for errors that can occur in downsampling from greater bit depth to less – it’s used in image processing as well as in sound. Well, that’s the claim, but is it mastering or encoding? To their credit, in the documentation Apple explains that their 32-bit process manages to encode from high-res audio without leaving a dithered footprint. Drag the high-quality files to the droplet, and presto-chango - out come files that all play perfectly in iTunes. But it would seem Apple has that all solved with their Master for iTunes droplet. Finding a good balance that keeps them all flowing together is an art in and of itself. It’s an interesting situation for a compilation release, in which styles range from ambient to muddy beats. In fact, the day of the announcement came right in the midst of reviewing masters for the release. The announcement of Apple’s new Mastered for iTunes suite caught me at a serendipitous time, as I prepped the first release on my new label. So we consider this the beginning, not the end, of this conversation. That to me isn’t a red flag for posting – quite the opposite, it’s an invitation. There’s so much to say, in fact, that almost each line here of David’s conclusions is up for potential discussion and debate. He tests this issue the only way that really matters: with his ears. More significantly, what does it mean that an increasing number of music listeners experience all music through Apple’s software as the final gateway to their ears? In our first look at this issue, we welcome guest writer and producer Primus Luta (David Dodson). What does it mean to “master for iTunes?” Apple tripped that question with the launch of a suite of utilities and sound-processing algorithms intended to master music for their codecs and software, rather than more generically as would be done with the CD. Here, writer David Dodson considers what that means (and similar issues with other digital music listening beyond Apple, like Spotify. One way or another, Apple is involved in a whole lot of the music to which people listen.
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