Re: HAL, AU or streams?
Re: HAL, AU or streams?
- Subject: Re: HAL, AU or streams?
- From: Brad Ford <email@hidden>
- Date: Tue, 4 Nov 2003 16:40:58 -0800
Wade,
I think you want to be working at the AudioUnit level (maybe even the
AUGraph level, depending on the kind of processing you want to do).
Remember, when you need access to lower level configuration of device
properties, the AudioOutputUnit has a passthru mode that proxies
AudioDeviceGetInfo/Get/Set properties to the HAL. So you get the
convenience of the higher level abstraction, and the detail provided by
the lower level HAL interface when necessary.
To pass properties through an Output Unit, the parameters map thusly:
AudioDevice params | AudioUnit params
----------------------------------------------------------------
inChannel <- inElement
isInput <- inScope (i.e.
kAudioScope_Input)
inPropID <- inID (use device property
ID's from AudioHardware.h)
Look at the example code (on Panther) in
/Developer/Examples/CoreAudio/Services/DefaultOutputUnit
-Brad Ford
QuickTime Engineering
On Nov 4, 2003, at 1:30 PM, Wade Williams wrote:
I've been reading up on CoreAudio, and I've got some confusion in my
head around what level of the API is appropriate for me to use.
I wish to record sound into buffers, and playback sound from buffers.
Almost always, the default input and output device will be used.
At some points in reading the documentation, I feel like it's best to
access the device at the device level. Other times it appears AU's
are the way to go. Finally, streams always seem interesting, but I'm
not sure exactly where they fit in.
Can someone give me some basic guidance?
Additionally, if someone knows of a simple example that records and
plays back sound, a pointer to it would be most appreciated.
Wade
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