@AJ113 Have you read the MAstering for Itunes PDF guide. Not because it’s about iTunes, but because it gives some interesting info on why mastering below 0db is a must for decent translation to their AAC format.

I confess, much of it’s beyond me, but I’m starting to do a little mastering work for others and researching brought me to it.

Yes, I have read it. It’s advising to master to below 0dB in order to avoid inter sample peak clipping. The level it advises to master to is -1db, which is more realistic than -0.3dB, but still may not be enough since inter sample peaks can reach higher than 1dB.

It also makes the point that it will not reject submissions purely on the basis that they generate clipping due to inter sample peaks (unless the clipping can actually be heard on playback). As I posted recently, I am of half a mind that none of this is worth bothering with if it doesn’t actually affect the music coming out of the speakers. I just analysed a random track from a Chickenfoot album, it had 25k inter sample peaks. I’m not saying that’s right or wrong but if it’s good enough for Sammy Hagar… I’m open to futher discussion though, I think there is probably a lot more to be brought to the table on this topic.

I’m glad you brought this pdf up, it also states:

Downsampling, as the word implies, is the process of using Sample Rate Conversion (SRC) to lower the sample rate (for example, from 96kHz to 44.1kHz). This process commonly creates aliasing, an undesired effect.

As I have explained elsewhere, I can hear degredation when a 48kHz project is rendered to 44.1kHz, so in my opinion it’s best to record at the same sample rate of the intended end product. And if you’re mastering for iTunes, that sample rate would be 44.1kHz, since it’s the MFiT standard.

Nevertheless, Apple seems to contradict itself when it recommends submitting masters of 24/96 for MFiT when it’s just advised against downsampling a few paragraphs earlier in the document. To me, that comes across as arrogant, (i.e. “no-one but Apple can downsample correctly”) but I may be misintepreting what they are saying.