Re: IOAudioEngine::performFormatChange cannot be triggered by change of I/O Buffer Size
Re: IOAudioEngine::performFormatChange cannot be triggered by change of I/O Buffer Size
- Subject: Re: IOAudioEngine::performFormatChange cannot be triggered by change of I/O Buffer Size
- From: Jeff Moore <email@hidden>
- Date: Tue, 02 Dec 2008 12:41:36 -0800
On Dec 2, 2008, at 12:22 AM, David Tan wrote: On the device window of HALLab, there’re combo box of Nominal Sample Rate and IO Buffer Size. While I change the selection of Nominal Sample Rate, I can get notification by IOAudioEngine::performFormatChange(). But it seems that change of IO Buffer Size cannot make it. My question is: what’s the IO Buffer Size really means? Hardware or driver?
That is the duration in sample frames of the IO cycle that the application is requesting. It is wholly separate from the buffers in the driver and the hardware. And If I want to be informed in the driver of its change, which method should I use.
About the only way you can monitor what buffer sizes the clients of your driver are using, is to override IOAudioStream::addClient and IOAudioStream::removeClient to observe as client buffers are registered and unregistered.
--
Jeff Moore
Core Audio
Apple
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