I might be misunderstanding, but I think that PDF is about how to master your music such that it will sound good after they convert it to AAC. It doesn't actually speak to the audio that's sent to them.

Can't source anything except our own deliveries to Apple, but we've been delivering PCM since ~2018. Likely earlier, that's just when the code got moved into source control. That actually predates the copyright on that PDF.

In general, of the maybe 150-odd DSPs we deliver to, as far as I know all but a handful have us deliver PCM. The remainder have us delivering flac.

> Can't source anything except our own deliveries to Apple, but we've been delivering PCM since ~2018.

Cool, I take your word for it. Thanks!

The referenced document only talks about AAC masters, and the tools at https://www.apple.com/itunes/mastered-for-itunes/ only create AAC masters. The simplest explanation is that the public materials and tools are just sadly out of date.

I'm pretty sure nucleardog is correct and that Apple wants 24/96KHz minimum sent to them; the PDF you linked to actually says that under "Best Practices" -- "To take best advantage of our latest encoders, use only 24-bit sources and send us the highest-resolution master file possible, appropriate to the medium and the project." Then Apple encodes their AACs using the tools and methods described in that document. If I understand it correctly, they're basically trying to ensure that the downsampling from 24/96 to 16/44 preserves as much information as possible. (Does it really make a difference? No idea. But it does mean that Apple has a whole lot of music they can re-encode at varying quality levels.)

It's odd because I've read that before and made an assumption that it was talking about AAC mastering, but it only implies that. There's nothing that comes out and says what they want! There are some parts where they suggest higher fidelity sources, but mostly it comes down to:

    Apple Digital Masters Droplet 
    You can use the Apple Digital Masters Droplet to automate the creation of 256 kbps 

AAC encodes.

There isn't actually anything about what you're supposed to send them, only the recommendation to use their tooling which seems geared to produce 256k AAC files.

Ah, that makes sense, thanks!