bills at apple.com
Fri Jun 24 16:36:32 PDT 2005
You raise an issue I thought would also be interesting for me to
With Tiger, Apple has also described a new audio file format - CAF
(Core Audio Format) Files.
There are a few fundamental issues we wanted to tackle with CAF:
(1) Should be audio format agnostic
- store anything from LPCM (big or little endian), 1-bit audio,
AAC, MP3, Ogg, Lossless (Apple, FLAC,..), etc...
(2) 64 bit clean data sizes
(3) Efficient and extensible
(4) Rich meta-data
It could fit in well with both the content and platforms that OpenAL
supports, so might have some value here as well.
There's a spec document available at Apple's developer web site:
http//developer.apple.com/audio (just do a search for CAF Files)
We anticipate making this broadly available (including sample code to
read these files that is platform neutral). In the meantime, Mac OS X
Tiger ships with support for reading and writing these files with the
AudioFile API. QuickTime 7 also offers support for reading these
files on previous Mac OS X (Panther) and Windows.
On 24/06/2005, at 4:12 PM, Garin Hiebert wrote:
> Great points from Bill. I'll add a few more comments that come to
> While stunningly efficient, ADPCM quality is pretty bad. Just
> worth taking into account.
> My limited experience with Ogg Vorbis seems to confirm points from
> Bill's post -- slightly better quality than MP3 for the same
> compression level, and pretty much the same in CPU hit (although
> Ryan's custom AL implementation for OS X should be even _better_
> because his implementation skips unneeded float-to-int-to-float
> One thing that I think is really good about Ogg Vorbis is that
> their "vorbisfile" API is really simple (yet flexible). We've used
> it for several projects here at Creative, and really found it to be
> very easy. How good things are on the API front with AAC I don't
> know, but with the lower CPU hit it is probably worth finding out...
> openal mailing list
> openal at opensource.creative.com
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