Re: Multiple HALAOUs don't get along?
Re: Multiple HALAOUs don't get along?
- Subject: Re: Multiple HALAOUs don't get along?
- From: James Coker <email@hidden>
- Date: Wed, 16 Jun 2004 11:53:36 -0600
You can only have one HAL output unit per AUGraph. That component
can do both input and output, but not with USB devices. Due to the
way the USB audio spec works, USB audio interfaces appear as 2 devices
to Core Audio,
one for input, one for output. So in addition to your AUGraph with your
FX and HAL output unit, you need to have another HAL Output Unit
running by it self (not in the AUGraph) that collects input and via
some callbacks, passes data to the first effect in your AUGraph.
It is all explained here:
http://developer.apple.com/technotes/tn2002/tn2091.html
There's been much discussion of this on the list, search
for postings with HAL Output Unit in the subject line.
Unfortunately, it is very not simple. However, as Bill Stewart has
recently hinted, there may be announcements at WWDC about
new CoreAudio features that may simplify things a bit.
Cheers,
Jim
On Jun 15, 2004, at 7:05 PM, Chilton Webb wrote:
Hi,
I wanted to use the HAL AudioOutputUnit to allow audio to pass through
a filter, to the output. However, Bill said that I can only have one
device per AU (currently). So I created two AUs, one for input, and
one for output. However, that doesn't work, for either internal or
external input (ie doesn't work at all).
So what is the simplest approach I can take to pass audio from a USB
mic, through a filter, and back out the speakers, in real time?
Thanks,
-Chilton
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