Recorded AIFF shows as AIFC

[mlind]

Today I tried recording in AIFF for the first time.
But my computer (Mac) tells me the files are AIFC (usually a compressed format) and not proper AIFFs.
The bitrate is over 1411 kbps, so it doesn't seem compressed, but the label is wrong.

[petur]

rockbox writes uncompressed AIFF
http://en.wikipedia.org/wiki/AIFF

[Llorean]

I think the question then becomes, what does MacOS use to claim the files are AIFC, and is it an issue of it improperly recognizing valid files, or an issue of invalid header information in our files for some reason?

[jhMikeS]

Funny cause the files headers are based on Apple's own specification of the format.

Audio Interchange File Format: "AIFF"
A standard for Sampled Sound Files
Version 1.3
Apple Computer, Inc.

The 'SSND' chunk makes no provision for compression. Though one thing comes to mind and that is the 80-bit floating point number written for the sample rate isn't fully normalized and maybe it reads that as AIFC even though floats don't have to be normalized to be the correct value. CoolEdit Pro writes the sample rate with the same exponent/mantissa as the encoder does. Perhaps a test patch that writes the float differently is in order.

[Llorean]

He did say the bitrate is *over* 1411... which shouldn't be the case, right?

[jhMikeS]

I don't know what MacOS will come up with if it sees a float in a form other than what it expects even if technically correct. It's the only thing I can think of that could be off since all the other data is just integers and the conversion is based on the IEEE standard + CoolEdit as a reference. I've just gotta see about subtracting one from the exponent and shifting the mantissa left by one. Maybe it'll do the trick.

Can you attach the header+something (first say, 200-300 bytes) of an AIFF MacOS recognizes correctly. Be sure it's 44100Hz Stereo as a reference. Can be binary form. Just post the original file's exact size in bytes in your reply.

[jhMikeS]

Well, 2822 could be the case if you record at 88.2Khz (x5) or 1536 if you record optical in at 48Khz (H120). Is it me or did I not see any details on the player and intended output?

[Llorean]

If I recall he's an H100 user, or was in the past at least (people do upgrade, apparently). I forgot about 48khz from Optical though.

[jhMikeS]

The long to float seems right. I can divide the mantissa by powers of two and increase the exponent accordingly and get the same samplerate but going the other way loses the left-justified 1 bit (which is always the highest order 1 bit in the integer form) and the wrong rate is read out on my PC (11332Hz). Sources seemed ambiguous about whether or not the h.o. '1' can be implied. It didn't seem so with IEEE754 extended but only with the smaller float sizes. Must be something else. Won't continue to bore everyone.   Still wanna see a sample header that MacOS shows correctly.

EDIT: Have to mention that 44100Hz 16bit Stereo PCM _is_ actually 1411.2Kbps...

[mlind]

OK...

iTunes (from Apple) says AIFF 1411 kbps.
Quicktime (from Apple) actually doesn't state the file format but says these (seven) particular files from the same recording is varying from 1410,76 to 1417,78 kbps... must be a value calculated in some stupid way.
Logic Pro (from Apple) has no trouble opening and using the files.
Waveburner (from Apple) says AIFF and has no trouble opening and using the files.

But still Mac OS X (10.4. says AIFC...

I opened one of the files in the program "File Buddy".
For every file there is a "Type" and a "Creator" - these can be changed by File Buddy.
There is also a presentation of what icon will be used, and beside that a label of the file type.

File Buddy said "Type:AIFF" & "Creator:no creator"
At the same time there was the label "AIFC" beside the icon (for an AIFC).
I changed Type & Creator to match another aiff I had on my computer.
The label beside the icon changed to AIFF.

Then I changed "Creator" back to "no creator" wich resulted in the label & icon changing back to AIFC.

I attached an AIFF made with iTunes. It's me saying "Hi" in swedish.



[attachment deleted by admin, too old]

[jhMikeS]

Maybe setting the extension to ".aif" instead of ".aiff" ?? I will record a short one and post a header comparison but I'm just curious. At first glance the header on your file looks identical to one recording would make.

[mlind]

Maybe setting the extension to ".aif" instead of ".aiff" ??

I tried that on my computer. No difference. And if that makes no difference then it won't make any difference to do it in RB either.

Actually, after my tests (see my previous post) I don't really care very much anymore.
The important thing is that the recorded files gets recognized by other apps.
(I'll also try with one or two others later)

It seems to me that it actually is a matter of strange behavour in Mac OS.
(Maybe I'll check with earlier versions of Mac OS)

[mlind]

...ooo...kay...

The "problem" is so far only present in my computer at home.
At work (with same OS version, and an earlier) the files shows as proper AIFFs.

Case closed.

[jhMikeS]

I guess something changed the "no creator" default mapping