Re: Playing 2 or more audio data simultaneously
Re: Playing 2 or more audio data simultaneously
- Subject: Re: Playing 2 or more audio data simultaneously
- From: Kurt Revis <email@hidden>
- Date: Wed, 18 Sep 2002 23:22:15 -0700
On Wednesday, September 18, 2002, at 01:23 PM, Robert Goulet wrote:
ok, ok. All of this sounds very useful... but how do I implement it??
I'm unable to find any example of how to use it... How are we supposed
to connect these AudioUnits?
Most of the examples in /Developer/Examples/CoreAudio/Services use
AudioUnits. Most of them use the default audio unit, and connect some
other AU to it.
There are two ways to connect two AUs.
1. Low level: Use AudioUnitSetProperty() on the destination AU, with
property kAudioUnitProperty_MakeConnection.
An example of this is in PlayEffect/PlayEffect.cpp, in
PlayEffect::UpdateAUChainIfNeeded(). It is described in
/System/Library/Frameworks/AudioUnit.framework/Headers/
AudioUnitProperties.h.
2. High level: Use an AUGraph to construct and connect a group of AUs.
An example is in PlayAudioFile/main.cpp, function CreateSimpleGraph().
See /System/Library/Frameworks/AudioToolbox.framework/Headers/AUGraph.h.
Isn't any complete documentation about a specific kind of AudioUnit
out there? I mean, I've found info about AudioUnits and their
properties... but nothing about using a "MixerAudioUnit".
There ought to be but there really isn't yet. Fortunately, given an
AU, you can find all of its parameters. The parameters have names, and
you can find the type and min/max values of each one, which helps a lot
in explaining things. See
AudioUnit.framework/Headers/AudioUnitProperties.h and
AudioUnitParameters.h.
(Also, the parameters for the Apple AU's are described, tersely, in
AudioUnitParameters.h.)
--
Kurt Revis
email@hidden
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