Question on Audio Built-in driver on latest Powerbook G4
Question on Audio Built-in driver on latest Powerbook G4
- Subject: Question on Audio Built-in driver on latest Powerbook G4
- From: Stéphane Letz <email@hidden>
- Date: Mon, 12 Dec 2005 12:51:40 +0100
Hi,
I'm testing our code on the latest Powerbook G4 1.67 / 512 Mo (OSX
10.4.3) and see some strange behaviour in the built-in audio driver:
- the driver does not work reliably with buffers of 64 frames: it
triggers regular kAudioDeviceProcessorOverload. This behaviour is
also seen using the MillionMonkeys test application and other
coreaudio applications. The same machine using the MOTU 828 FireWire
driver doe not shows the problem: it works OK at 64 frames and even
32 frames.
- running our code at 128 frames, our process consume something like
13% CPU. Using Shark to profile the code, it appears that the Built-
in driver consume a lot of time in AppleDBDMAAudio::clipOutputSample
and IOAudioStream::readInputSamples and in particular in functions
like "eqalizer, bassEnhance, and dynamicRangeControl". Moreover these
functions seems not to be Altivec accelerated. What is the purpose of
these functions and why are they consuming so much CPU?
Thanks
Stephane Letz
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