Re: Problem with Alesis MultiMix 8 USB 2.0 and kAudioDevicePropertyStreamConfiguration
Re: Problem with Alesis MultiMix 8 USB 2.0 and kAudioDevicePropertyStreamConfiguration
- Subject: Re: Problem with Alesis MultiMix 8 USB 2.0 and kAudioDevicePropertyStreamConfiguration
- From: Jeff Moore <email@hidden>
- Date: Wed, 29 Aug 2007 11:31:55 -0700
On Aug 29, 2007, at 7:26 AM, Stefan Haller wrote:
We are experiencing strange behaviour with the Alesis MultiMix 8
USB 2.0, and I was wondering if there are any known problems with it
(or
its driver), or whether we might be doing something wrong.
Not really. This property is something the HAL synthesizes from the
stream layout of the device.
Here's what happens: we query the input side of the device for
kAudioDevicePropertyStreamConfiguration, it returns one buffer with 10
channels, which is what we expect. Then we set the sample rate
(kAudioDevicePropertyNominalSampleRate, isInput = true), and after
that
we query kAudioDevicePropertyStreamConfiguration again; this time it
returns one buffer with 0 channels (and 0 mDataByteSize). This
strikes
me as a driver bug; I can't quite imagine what we might be doing wrong
here.
Then we start the device, and in the IO proc we get the expected
buffer
list (one buffer with 10 channels), which doesn't match what the last
query of kAudioDevicePropertyStreamConfiguration had returned.
Any ideas?
This sounds like you are asking the HAL for the stream configuration
in isolation and are getting an intermediate state of the device. Are
you waiting for the notifications from the HAL about things changing
or just assuming that your change took place after setting the sample
rate?
--
Jeff Moore
Core Audio
Apple
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