Re: Audio Converter and Endians problem
Re: Audio Converter and Endians problem
- Subject: Re: Audio Converter and Endians problem
- From: Jeff Moore <email@hidden>
- Date: Mon, 27 Jan 2003 18:15:46 -0800
If you want to see what an AIFC file that has little endian data in it
looks like, you can make one using QuickTime.
The following format IDs found in the Extended Common chunk (or
whatever it's called) indicate little endian data:
k16BitLittleEndianFormat
k32BitLittleEndianFormat
In addition, some AIFC files will have a WAVE chunk that contains the
flag that says it's little endian. The constants are in Sound.h.
All of this is part of the AIFC specification and have been in use for
years. As Bill said, the AudioFile API will sort you out for handling
the differences and getting Core Audio representations of the
information.
On Monday, January 27, 2003, at 04:25 PM, Richard Dobson wrote:
I didn't think an AIFF-C file could contain little-endian data, any
more than an AIFF file can. How on earth is this indicated? An AIFF-C
file, like AIFF, starts with the 4-byte tag <FORM>, followed by a
4-byte chunksize, followed then by the tag <AIFC> - and the FORM
chunksize must surely be big-endian in all cases, as that is what is
expected. It would seem to be impossible to define an AIFF-C file to
be either little or big-endian, to begin with!
My document describing AIFF-C is admittedly somewhat elderly (vintage
1991); but I haven't seen one anywhere that is newer. That document
expressly describes all data as big-endian, everywhere. Any pointers
to more up to date specifications would be most welcome.
Richard Dobson
Franck Stauffer wrote:
Le mardi, 28 jan 2003, ` 00:04 Europe/Paris, Bill Stewart a icrit :
They are AIFC files - AIFF cannot legally contain either little
endian or float data
Yeah i knew and even checked those files were AIFC...
I would hope that the AudioFile changes in 10.2.3 would correctly
describe these as AIFC files as little-endian based files
Well i guess i should check the version of my Frameworks then.
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--
Jeff Moore
Core Audio
Apple
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