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: Fri, 31 Aug 2007 14:09:44 -0700
On Aug 31, 2007, at 12:41 PM, Stefan Haller wrote:
Jeff Moore <email@hidden> wrote:
Changing the format of the device (and in fact most other changes to
device state) is an asynchronous operation. Always has been. That's
why the HAL has so many notifications. You can't assume that an
operation has succeeded just because you didn't get an error when
setting the property. Your app has to pay attention to the
notifications in order to know when the change has actually taken
effect.
We are aware of this and plan to clean up our code accordingly in a
future version. This didn't have high priority for us so far, because
our current code used to work fine with every device we tested.
Like I said, lucky.
And in fact, in this particular case I don't believe that this is the
problem either, or at least that listening for notifications would
help:
when we register a device property listener for '****', it is not
called
when we change the sample rate of the MultiMix from our code. We do
get
notifications when we set the sample rate of other devices, and we do
get notifications when another process changes the sample rate of the
MultiMix; just not when we do it.
The same behaviour can be seen in HALLab: when another process changes
the sample rate of the MultiMix, HALLab gets notifications about this,
but when you change the sample rate in HALLab itself, it doesn't. For
other devices, it gets notificications in either case.
If you have an exemplar of this device and could have a look at
this, it
would be greatly appreciated.
I don't have one of these devices. But from your description, it
sounds to me like the driver for the device is a little flaky. It
doesn't sound like it is using our driver, so you might want to show
the problem to Alesis.
--
Jeff Moore
Core Audio
Apple
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