default output start & stop
default output start & stop
- Subject: default output start & stop
- From: papi <email@hidden>
- Date: Sun, 05 Jan 2003 09:55:23 -0800
New to core audio -- still pretty green at C++.
The DefaultAudioOutput example project's TestDefaultAU() function has
some
code that starts and stops a simple sine wave render. Can someone
explain
in further detail what exactly is happening here? (I've copied the
snippet below.)
I'm wrestling audio output start and stop in a simple app using Carbon
controls.
My start button calls a function that contains AudioOutputUnitStart();
my stop
button calls a function that contains AudioOutputUnitStop(). Sounds
reasonable, but ...
What does usleep() do? I can't find it in a search of any of the
frameworks included
in the project.
How is CFRunLoopRunInMode called? It's not an explicit call, since the
only mention of it is in a comment string.
The last comment says to stop the AU; but then continues by saying that
the process is already nuked. How? Where?
My best guess on all this is that the usleep() function causes something
somewhere to sleep for 5 seconds -- allowing the tone to be played --
before the AU is stopped by AudioUnitStop(). But:
commenting-out the AudioUntiStop() function, the tone still plays
for 5 seconds; so something else is stopping it.
commenting-out the usleep() function causes no sound to be played;
now that's puzzling.
So my guess isn't entirely correct.
Thanks in advance!
Scott
// Start the rendering
// The DefaultOutputUnit will do any format conversions to the
format of the default device
verify_noerr(AudioOutputUnitStart(theOutputUnit));
// RUNS FOREVER!!!!
// we call the CFRunLoopRunInMode to service any notifications that
the audio
// system has to deal with
usleep (5 * 1000 * 1000); // sleep for 5 seconds
// REALLY after you're finished playing STOP THE AUDIO OUTPUT
UNIT!!!!!!
// but we never get here because we're running until the process is
nuked...
verify_noerr(AudioOutputUnitStop(theOutputUnit));
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