Has AIFF data format quietly changed (to little endian)?

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Has AIFF data format quietly changed (to little endian)?

Has the Apple AIFF format quietly changed in some way -- perhaps from 16-bit big endian to 16-bit little endian?

I find that in some older audio software, the "AIFF" files that Tiger creates for me (dragging audio-CD audio to the Desktop) either won't open, or automatically "convert" on opening, or play as noise.

(I wonder if a switch to little-endian format might have some benefit on Intel... but then, you could play old style AIFFs on Intel years ago if you had an app that could handle them...)

It all seems to be a top secret mystery as I can't find anything on the subject on the Web or developer.apple.com.

Posted on Apr 1, 2007 6:04 AM

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Answer 1

LittleBigEnd Author

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Apr 1, 2007 11:03 PM in response to LittleBigEnd

Well a bit more research, and everything's still vague, but it looks like:

- Apple wanted to switch to little endian for some reason with OSX (maybe better for writing CD audio from iTunes? maybe anticipating Intel transition??)

- Normal AIFF format doesn't allow this, so they created an AIFF-C "compressed" codec that actually isn't compressed -- it's non-compressed audio, with the only difference being the byte order

- This should be identified with a .aifc extension, but it looks like they wanted to make the switch transparent to everyone

- It's so transparent, almost no one has noticed it happened

- When iTunes uses the term "AIFF" it actually means AIFF-C/little endian codec

- When you drag audio-CD audio to the Desktop, you're actually getting AIFF-C/little endian files

- This will never affect you in any way unless you are using some older 3rd party audio software that can't read the codec. Big endian vs. little endian is identical sound quality and the two can be converted back and forth without sound quality loss.

- You can still create and use normal (big endian) AIFF files, it's just the OSX OS and Apple apps that are choosing to use the little endian format.

- None of this should be confused with the entirely different -- and openly identified -- newer "Apple Lossless" format, which really is compressed.

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Answer 2

LittleBigEnd Author

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Apr 2, 2007 9:03 AM in response to LittleBigEnd

I forgot to mention, the "compressed" little endian codec is technically called "sowt".

(Absolutely zero information available as to what "sowt" stands for.)

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Answer 3

Apr 3, 2007 7:54 PM in response to LittleBigEnd

'sowt' is the byte-reverse of 'twos', the normal LPCM format. (clever)
The name 'twos' refers to the fact that the data is stored as two's complement integer data.

As for your original question, all I can tell you is that CoreAudio and QuickTime 7 are very flexible and can handle LPCM data as big or little endian integer or float. Old programs might not have this ability.

-Ken

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