Re: "Channel" confusion
Re: "Channel" confusion
- Subject: Re: "Channel" confusion
- From: Laurent Cerveau <email@hidden>
- Date: Thu, 14 Jun 2001 09:14:26 -0700
On Wednesday, June 13, 2001, at 06:52 PM, Scott Lehman wrote:
>
For example, should the driver for a sound card with analog and digital
>
outs present itself as one output device? How many channels?
From a driver point of view you have three main entity to manipulate :
-> the device (IOAudioDevice) does the represent the complete piece
of hardware, Ususally the driver inherit from IOAudioDevice object :
this is needed to have it being recognized by CoreAudio HAL.
-> The IOAudioEngine
-> The IOAudioStream
I'll explain mnore the 2 latest ones : the IOAudioEngine can be
considered
as the "data pump" that will move the audio data in and/or out the
computer.
You usually need to subclass one in your own driver.
Now that doesn't describe what is transferred on this data pump : and
this
is the IOAudioStream. So for example if you have a device with input and
output
capabilities, you could either represent it as
+ two IOAudioEngine each one with one stream
+ one IOAudioEngine with two streams : one for input one for output.
The choice will be made ususally depending on the way you do
synchronization
between the input and output part.
Laurent
Laurent Cerveau
AudioCPU SW - Manager
Apple Computer Inc.
email@hidden