Re: Streaming audio to built-in audio device
Re: Streaming audio to built-in audio device
- Subject: Re: Streaming audio to built-in audio device
- From: "B. Mitchell Loebel" <email@hidden>
- Date: Sun, 06 May 2007 17:58:00 -0700
Hello Andrew, Mark, and others on this list:
Please ... let's not go into PC deprecations ala "I've never met a
decent C programmer who can't follow simple C++ or ObjC
samples". I'm looking for a solution in C; if you can help, I'd very
much appreciate ... if not, please don't waste my time and that of other
readers.
Complicated coding is not my problem. Rather its Apple's many extensions
to C that I don't have time or desire to learn ... I'd like to cut my
usage of them to a bare minimum.
Cutting to the chase ...
The solution I'm seeking doesn't have a user interface ... my host app
does that. So I'm looking for a code snippet to hard wire into my app.
I'm not even looking for a plug-in because that implies dynamic loading
by my app at launch time.
I did some looking in the Apple refs and came up with TN2097,
DefaultOutputUnit, and the notion of an
AudioStreamBasicDescription struct. I can assign all the parameters
that are important to me into that struct ... good. I also saw a way to
set up a renderCallback method ...
- "that will be used as the input procedure when rendering data to
the AudioUnit. The input procedure will be called only when the Audio
Converter needs more data to process" (quoting TN2097)
Question ..
how do I instantiate the
DefaultOutputUnit without having to become a Component Manager
expert ;-).
TN2097 described how I should bind a renderCallback method into the AU
... good. I see where the Audio Unit is the 'consumer' of my data ... my
app is the 'producer'. Having told the Audio Unit the size and shape of
my frames (my app will load a buffer with a frame for the Audio Unit to
'pull'), I'd like to pass a pointer to the AU when it needs more data to
drive its D/A and speakers. I saw somewhere that the renderCallback is
supposed to return a ComponentResult, but I can't find out what that
looks like ...
question. I do know
what my renderCallback function needs do to create the pointer to my
buffer ... my app does that coding.
Finally, I need to know how to start and stop the Audio Unit
engine.
I think most of the questions I've raised would be answered if I could
find a
list of functions associated
with the DefaultOutputUnit ... in
C.
Are you able to point me there please?
Good comments Andrew ... well taken.
On May 4, 2007, at 1:34 PM, B. Mitchell Loebel wrote:
Hello:
I have an app that creates a PCM stream. Where can I find the API
(and perhaps some examples) to interface with the built-in D/A to
send my audio to the built-in speakers please?
B. Mitchell Loebel, Executive
Director
408 425-9920
The Tech Startup Connection
(formerly The PARALLEL Processing Connection)
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