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Re: IO Buffer Size Range
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Re: IO Buffer Size Range


  • Subject: Re: IO Buffer Size Range
  • From: Jeff Moore <email@hidden>
  • Date: Tue, 19 Aug 2008 22:51:04 -0700


On Aug 19, 2008, at 10:19 PM, AI Developer wrote:

How does the CoreAudio/HAL determine the I/O buffer size range for a device/driver?

This is the range that's retrieved by kAudioDevicePropertyBufferFrameSize property.

The maximum value seems to be related to the value passed to IOAudioEngine::setNumSampleFramesPerBuffer() by the driver.

But it's not obvious in terms of what the relationship is between the two.

Currently for IOAudio-based devices, the minimum is always however many frames fit into 300 microseconds (for example 14 frames at 44100). The maximum is always 3/8ths the number of frames in the ring buffer.



Is there a way that a driver can directly control these values?

The only influence the driver has is through it's control of the size of the ring buffer.


--

Jeff Moore
Core Audio
Apple


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