Re: HAL Devices and Streams
Re: HAL Devices and Streams
- Subject: Re: HAL Devices and Streams
- From: Jeff Moore <email@hidden>
- Date: Fri, 11 Jan 2002 16:22:35 -0800
on 1/11/02 2:44 PM, email@hidden <email@hidden> wrote:
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I've noticed on OS X (up to 10.1.2 at least) QuickTime doesn't seem to have
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the same access to multiple audio devices as OS 9, namely USB audio.
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The list of available audio devices QuickTime API's FindNextComponent and
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GetComponentInfo functions give is limited to FireWire DV, and two
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variations of "HAL System". In contrast, under OS 9 with a USB audio device
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connected (Griffin iMic), QuickTime has access to both "Built-In" and "USB
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Audio", as it should.
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Is this a limitation of the current QuickTime on OS X, or CoreAudio? What
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will be done about this limitation in the future?
The Sound Manager provides an sdev component to talk to the HAL. It is the
default component. This component by default talks to whatever the HAL
thinks of as the default device. This provides pretty much the expected
behavior.
Since the Sound Manager is shimmed on top of the HAL and doesn't provide an
API that abstracts out the device discovery process (like the Sound Input
Manager does), it isn't feasible to provide a component for every device the
HAL knows about since they can come and go pretty much at will. Therefore,
it has just the one sdev component, but this component provides a mechanism
to tell this it what HAL device to use (the siHALAudioDeviceID Get/SetInfo
constant).
Given how the Sound Manager works, it really isn't going to be possible to
make it work the way you would like on X.
--
Jeff Moore
Core Audio
Apple