bills at apple.com
Fri Jun 24 15:15:50 PDT 2005
Garin, (and others interested)
AAC - the main audio codec in MPEG-4, makes a very attractive format
for games I think. There were two explicit design goals with AAC - it
was developed by the same people who developed MP3.
(1) Decode CPU requirements should be minimal
(2) Quality of encoding should be better - thus smaller files for the
So, when we compare AAC with MP3, the two areas we compare are:
AAC at 128kbps is about the same as MP3 at 160kbps
- from public listening tests, Ogg is about the same as AAC
(2) Decode CPU Usage:
AAC's decode is extremely efficient - On a G4 1GHz iMac decode
is less than 1% CPU (about 0.8%). On a G5 it is about 0.2 - 0.3 %
MP3 decode - On a G4 1GHz iMac decode is less than 2.4% CPU
(about 0.8%). On a G5 it is about 1 %
I've no idea what Ogg's performance characteristics are
There are some open source AAC efforts (faac) as well (though I don't
know what their performance/quality characteristics are), as well as
various options for hardware based decoders for embedded devices.
It is an open standard.
On 24/06/2005, at 2:46 PM, Garin Hiebert wrote:
>> Speaking of audio compression, I was wondering about ADPCM. It is
>> my understanding that the decoding is done by the main processor
>> for all (??) OpenAL backends. This is the main reason I'm shying
>> away from it. Even the old Playstation would do this on the SPU/
>> DSP... so I was wondering if Creative has any plans to support
>> this in their native drivers?
> It's been considered, but ADPCM decompression is extremely
> efficient, so it hasn't been a major issue. ADPCM as well as more
> CPU-intensive formats such as Ogg Vorbis or MP3 are certainly still
> being considered...
>> I suppose in lieu of this we need the equivalent of the OpenGL
>> shading language for sound DSPs; but I won't hold my breath.
> Even if we had such plans, it still wouldn't be a good idea to hold
> your breath until it's done.
> openal mailing list
> openal at opensource.creative.com
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