Re: Audio Sources?
Re: Audio Sources?
- Subject: Re: Audio Sources?
- From: Laurent Cerveau <email@hidden>
- Date: Thu, 1 Nov 2001 22:02:51 +0100
On Thursday, November 1, 2001, at 04:06 PM, email@hidden wrote:
When I initialize the audio devices I get one for input and one for
output.
However I do no see mutplie sources such as microphone, line in etc...
I assume
that the built in device only has one source. How do I get the
information
about the source ie: is it digital or analog etc...
Physically the audio is pumped in/out on a bus that is between the
mac-io controller and the audio codec (Screamer, Texas, Burgundy or
Daca) . This is either I2S (for DACA and Texas ) or DavBus (Screamer and
Burgundy) . If you are interested in driver development, you can look at
this looking at the device tree plane in IORegistryExplorer App.
So basically you have only one input stream and one output stream of
data between the IO controller and the audio codec. However the Codec
can route this one to/from different input port that are then connected
(or not) to built-in, external mic and so on.... Note that the CD that
appears on 9 is not physically connected to the Codec (CD path is
digital on 9) and that the modem that appears on 9 will not on X (what
sense has a modem in an audio system :-)) even if it can occupy one
physical codec input.
In the kernel this is represented by an input selector IOAudio control.
From user land , I am not sure ,probably the
kAudioDevicePropertyDataSources, but Jeff could certainly confirm or
infim me (especially if I have it wrong :-))
The built-in source is always an analog one (and then of course there is
a DAC in the Codec to do the conversion to digital data.)
Laurent Cerveau
Applications Division
Apple Computer Inc.
email@hidden