Re: kAudioHardwarePropertyDevices + USB devices
Re: kAudioHardwarePropertyDevices + USB devices
- Subject: Re: kAudioHardwarePropertyDevices + USB devices
- From: Jeff Moore <email@hidden>
- Date: Wed, 30 May 2001 12:03:44 -0700
on 5/30/01 5:51 AM, Markus Handell <email@hidden> wrote:
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I'm having problems with CoreAudio and using USB output devices. More
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specifically, it's the device list that doesn't seem to be synchronized
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with the
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actual hardware devices connected to the computer.
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Problem scenario:
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1) I have the following devices connected:
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a) Built-in audio controller
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b) Philips USB Digital Speaker System (MA-150U)
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c) Soundsticks
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These are all reported by CoreAudio on application startup.
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2) I unplug the Soundsticks. CoreAudio now correctly reports the device
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list
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change and only the two remaining devices are in the device list.
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3) I reconnect the Soundsticks. CoreAudio reports of a device list
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change, but
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the Soundsticks doesn't appear when I request the list.
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The same happens with the Philips speakers too. The strange thing is
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that they all appear correctly when I restart my application!!!
This is a known issue that I'm fairly certain is restricted to USB devices.
The problem is that the HAL is getting device list notification from IOKit
prior to the driver actually being fully initialized. Specifically what is
happening is that when the HAL scans the new device for it's IOAudioEngine
objects. At that point, the driver is reporting that it has none due to the
fact that it is currently being initialized, so the HAL drops that device
from the device list.
--
Jeff Moore
Core Audio
Apple