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Notes on Core Audio Implementation of PortAudio
by Phil Burk and Darren Gibbs
Document last updated March 20, 2002
WHAT WORKS
Output with very low latency, <10 msec.
Half duplex input or output.
Full duplex on the same CoreAudio device.
The paFLoat32, paInt16, paInt8, paUInt8 sample formats.
Pa_GetCPULoad()
Pa_StreamTime()
KNOWN BUGS OR LIMITATIONS
We do not yet support simultaneous input and output on different
devices. Note that some CoreAudio devices like the Roland UH30 look
like one device but are actually two different CoreAudio devices. The
BuiltIn audio is typically one CoreAudio device.
Mono doesn't work.
DEVICE MAPPING
CoreAudio devices can support both input and output. But the sample
rates supported may be different. So we have map one or two PortAudio
device to each CoreAudio device depending on whether it supports
input, output or both.
When we query devices, we first get a list of CoreAudio devices. Then
we scan the list and add a PortAudio device for each CoreAudio device
that supports input. Then we make a scan for output devices.
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