'Mastered For iTunes' guidlines from Apple

[Lagerfeldt]

In my tests the AAC format is prone to create larger inter-sample peaks than MP3.

Apart from recommending that you don't clip, Apple seems to advocate a peak level of -1dBTP, which in any case would take care of most (but not necessarily all) ISP's.

The AURoundTripAAC Audio Unit plug-in mostly looks like an ISP meter, but I haven't checked it out yet.

[NYCruiser]

Wow

[Cheebs Goat]

Well, that PDF assaults the reader with a torrent of bullshit right out of the gate.

...but when you finally get to the tech details there is actually useful information in there. On a side note, I wonder why they still force the encoder to use 44.1. Surely iStuff plays back many different sample rates, right?

[Lagerfeldt]

It's not BS free, I agree. But any focus on sound quality is a step in the right direction.

[rhythminmind]

Originally Posted by Cheebs Goat

I wonder why they still force the encoder to use 44.1.?

To let the encoder focus on the audible range. If your encoding a 96khz file, without filtering majority of the bitrate is used for non-audible content. If the goal is better compressed audio quality, lower samplerates make more sense.
As with PCM bitdepth/dynamic range will have more of an impact/audible benefit then doublerate samplerates.

[Cheebs Goat]

Doh! It sounds so obvious when you put it that way... Thanks!

[duke89061]

This is a positive development in theory, but under what circumstances is the mastering engineer doing the AAC encoding?

With major labels, the masters are submitted and some lackey at the label submits them to Apple, and with an indie project, the wav files are supplied to TuneCore or ReverbNation.

How would a mastering engineer go about having a recording designated as "Mastered for iTunes"?

[BubbaMc]

Originally Posted by Lagerfeldt

It's not BS free, I agree. But any focus on sound quality is a step in the right direction.

Then they should just use ALAC and be done with it.

[NYCruiser]

If you read the guide for the plug, it isn't so the mastering engineer can provide the aac encoding. It is just so the engineer can apply the coding to check how his master will sound when it gets encoded. Apple is clear that they don't want you to submit the encoded version to iTunes. It just lets you accurately hear what the mix will sound like encoded so you can make any adjustments you want before submitting it. Actually a very cool thing for apple to provide instead of just letting a mastering engineer guess when its right.

[Rick Hoekman]

So after checking the 24/96 file for ISP and submitting it to Apple they will convert the file into a 256 kbps AAC format? Or is it at a higher rate?

Ah, found it:

Then, encode to AAC: 2. To convert to iTunes Plus AAC, type on one line:
afconvert intermediate.caf -d aac -f m4af -u pgcm 2 -- soundcheck-read -b 256000 -q 127 -s 2 final.m4a

[Waltz Mastering]

Originally Posted by BubbaMc

Then they should just use ALAC and be done with it.

Yep.

[Cheebs Goat]

Originally Posted by NYCruiser

If you read the guide for the plug, it isn't so the mastering engineer can provide the aac encoding. It is just so the engineer can apply the coding to check how his master will sound when it gets encoded. Apple is clear that they don't want you to submit the encoded version to iTunes. It just lets you accurately hear what the mix will sound like encoded so you can make any adjustments you want before submitting it. Actually a very cool thing for apple to provide instead of just letting a mastering engineer guess when its right.

what would be even better is if they provided a plug to audition the effect of Sound Check or whatever it is they call their volume control feature.

[NYCruiser]

Once you use the plug to perform their conversion, you can bounce it into iTunes and just run soundcheck for yourself. Then you will know. I think the plug actually gives you an apple converted version to check out in advance. They just don't want you to submit the converted version, because they will be running conversion on it again.

[Rick Hoekman]

Originally Posted by Cheebs Goat

what would be even better is if they provided a plug to audition the effect of Sound Check or whatever it is they call their volume control feature.

There is an plugin provided which does this.

[Cheebs Goat]

Originally Posted by NYCruiser

Once you use the plug to perform their conversion, you can bounce it into iTunes and just run soundcheck for yourself. Then you will know.

But the real advantage would be if you could test Soundcheck in real time. As you were working you could see, for example, that your mastering was giving you 6 db of gain reduction/makeup gain, but Soundcheck was dropping the whole thing by about 6 db...so no good. Then you could adjust things in real time until maybe you found a setting where you were getting 3 db of reduction/makeup gain and Soundcheck was dropping the whole thing by 1.5 db. Then you would know you were getting somewhere.

If it was real time, you could find the exact line where you start pissing in the wind and then not cross it, possibly saving countless songs.

[UncleBubba]

anybody wonder why this even exists???

OK I'll bite...

...BECAUSE iTUNES SOUNDS HORRENOUS...or rather the AAC format in iTunes does!!!!

it is THE WORST representation of the music you put online...(myspace does;t count anymore does it?)

hands down...Apple should be ashamed at their nonsense...how about just letting folks put MP3's that they themselves have encoded (properly) on there???

why on earth do they need to encode to AAC...it basically sounds bad...always on everything I listen to on iTunes.

FO a company that has made BILLIONS off of musical content...you think they would be leading the way with their player...it is archaic...and riculous


...hey anybody wanna hear what I really think?

[NYCruiser]

If I'm not mistaken Sound Check is the application in iTunes that tries to make all the songs loaded into iTunes play at the same volume. Kind of a multi-song normalization. So, it seems that the affect it will have on the song you are mastering would depend on the rest of the songs that are in any individual iTunes library. Maybe I understand it wrong, but it seems like trying to master to that would be like shooting pool with a piece of rope.

[Cheebs Goat]

On the ACC thing, I know what you mean (two posts up). It is puzzling that they do not let studios sell their songs in whatever format they like in addition to 256 kbps ACC. It wouldn't be any skin off of Apple's nose if the download link led to a 24 bit 48 kHz file instead of an ACC. They'd barely even have to do anything aside from allow the file exist.

[Cheebs Goat]

Originally Posted by NYCruiser

If I'm not mistaken Sound Check is the application in iTunes that tries to make all the songs loaded into iTunes play at the same volume. Kind of a multi-song normalization. So, it seems that the affect it will have on the song you are mastering would depend on the rest of the songs that are in any individual iTunes library. Maybe I understand it wrong, but it seems like trying to master to that would be like shooting pool with a piece of rope.

I'm 99% sure that Sound Check sets songs to a defined standard level, not a level based on the songs around it...Unless the "album" feature is checked. Even then, it sets the album level to a set standard without taking external songs into account.

[siddhu]

Originally Posted by UncleBubba

anybody wonder why this even exists???

OK I'll bite...

...BECAUSE iTUNES SOUNDS HORRENOUS...or rather the AAC format in iTunes does!!!!

it is THE WORST representation of the music you put online...(myspace does;t count anymore does it?)

hands down...Apple should be ashamed at their proprietary nonsense...how about just letting folks put MP3's that they themselves have encoded (properly) on there???

why on earth do they need to encode to AAC...it basically sounds bad...always on everything I listen to on iTunes.

FO a company that has made BILLIONS off of musical content...you think they would be leading the way with their player...it is archaic...and riculous


...hey anybody wanna hear what I really think?

AAC audio is not proprietary to Apple. It's just that apple was the first major company to implement it and adopt it.

AAC was developed with the cooperation and contributions of companies including AT&T Bell Laboratories, Fraunhofer IIS, Dolby Laboratories, Sony Corporation and Nokia. It was officially declared an international standard by the Moving Picture Experts Group in April 1997. It is specified both as Part 7 of the MPEG-2 standard, and Subpart 4 in Part 3 of the MPEG-4 standard.

Official page is here

[touch]

Originally Posted by UncleBubba

...hey anybody wanna hear what I really think?

Haaa, now tell us how you feel about the amp-quality in ipods.

[Bob Olhsson]

AAC files made with the Nero or Fraunhofer professional codec sound great.

[mmarra]

Just some further lituature that was posted in the last couple of days regarding mastering for iTunes.

Mastered for iTunes: how audio engineers tweak music for the iPod age

I get many requests that the final output/medium will be digital (mp3 or acc) since I work with alot of indie clients who place their music on iTunes, their website or other services and was think of getting the Sonnox Fraunhofer Pro-Codec Plug-In to hear what my masters might sound like in a digital format. The only issue with the Sonnox plugin is that it is fairly expensive but I' going to just have to bit the bullet as I think demand for digital master outputs will be more common.

[UncleBubba]

AAC soft to my ears...always soft around the edges...in iTunes...no idea how they code it

OK so proprietary may be the wrong word...how shall I put this then...EXCLUSIONARY!!!!

Apple's EXCLUSIONARY practices are a joke...a real joke...what kind of company dealing with music...doesn't allow MP3s...there are many that think (myself included of course) that MP3 are heads and tails over AAC...and just generally prefer other formats for lower storage type files...

Please go and listen to your fav music at the iTunes store...it truly is an abomination...whatever they are doing it is wrong.

And they are way behind what is happening...like players that will play any file...and site that allow purchases of hi and low res (for lack of a better term)...basically whatever you want.

Really 44.1/16 is so 20 years ago...no really...24 it files please...no more dither please...no more crappy converting to AAC please...



@ Bob O...maybe certain conversion is nice for AAC...but I haven't heard it and Apple certainly isn't using it.


PS an international standard my arse...we have been force fed the thing because iTunes is IT right now.

[Cheebs Goat]

Originally Posted by UncleBubba

Really 44.1/16 is so 20 years ago...no really...24 it files please...no more dither please...no more crappy converting to AAC please...

You're half in luck. The mastering guide linked in the first post said Apple prefers to encode for iTunes at 24 bit with no dither, and will do so if you give them a 24 bit source file.

...but it will still be 256 kbps ACC.

[Bob Olhsson]

Originally Posted by Cheebs Goat

. The mastering guide linked in the first post said Apple prefers to encode for iTunes at 24 bit with no dither, and will do so if you give them a 24 bit source file.

...but it will still be 256 kbps ACC.

The encoding actually IS really smart dither. This doesn't mean not dithering to 24, it means not dithering to 16.

[Greg Reierson]

Originally Posted by Cheebs Goat

you could see, for example, that your mastering was giving you 6 db of gain reduction/makeup gain, but Soundcheck was dropping the whole thing by about 6 db...so no good. Then you could adjust things in real time until maybe you found a setting where you were getting 3 db of reduction/makeup gain and Soundcheck was dropping the whole thing by 1.5 db. Then you would know you were getting somewhere.

Is that really the goal? Gaming the system to make a song louder in the context of other music is only going to annoy the listener. Making a whole album louder is also meaningless since there is no context.

Soundcheck and other systems like it make the loudness game irrelevant.


GR

[UncleBubba]

Originally Posted by Cheebs Goat

You're half in luck. The mastering guide linked in the first post said Apple prefers to encode for iTunes at 24 bit with no dither, and will do so if you give them a 24 bit source file.

...but it will still be 256 kbps ACC.

did not know that...that's a good start!!!..

[surflounge]

just did a listening test between same song as:
FLAC
AIFF
MP3 @320
and M4a using "mastered for iTunes" droplet

how do you expect the M4a to NOT sound the worst?
Only benefit is the lightest file size.
More kids in their garage calling themselves 'mastering engineers' now, cranking out compressed crap without knowing the ear damage it's causing. Bad call to associate this with mastering.
Please give us 24/96 format that will play on iPods.