IO proc no longer being called
IO proc no longer being called
- Subject: IO proc no longer being called
- From: Jeremy Todd <email@hidden>
- Date: Fri, 17 Jun 2011 16:28:31 -0400
Hi,
I'm seeing a strange behavior where our IO proc quietly stops being called. We have an aggregate device which aggregates user-selected input and output devices. This behavior occurs with some combinations of devices including "built-in line output" and "built-in output" on a Mac Pro (10.6.7). It doesn't occur with some other combinations of devices (e.g. using one of the external USB devices we have here).
The IO proc stops after we show a dialog to let the user select an audio file. When the user clicks on the file, finder shows a little preview window and presumably interacts with the audio hardware to prepare to play it. If the user cancels the dialog and returns focus to the app, our IO proc has quietly stopped being called.
I registered using AudioDeviceAddPropertyListener() for everything I thought was relevant (kAudioDevicePropertyDeviceIsRunning, kAudioDevicePropertyDeviceIsRunningSomewhere). After the dialog is closed, I get a notification that kAudioDevicePropertyDeviceIsRunningSomewhere has changed, but both kAudioDevicePropertyDeviceIsRunning and kAudioDevicePropertyDeviceIsRunningSomewhere are TRUE, even though my IO proc isn't being called anymore.
Interestingly while the dialog is open, the IO proc does continue to be called. So it's like when the preview window is destroyed, it does something to take out audio IO for the current process, but our audio engine is not notified of this.
Is it possible that this is a bug related to finder interacting with the audio hardware from within our process itself (if the preview window is even in the same process, I'm not actually sure about that)? Or is there some other way we can receive reliable notifications when our IO proc is not going to be called anymore?
Regards,
Jeremy
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