Re: HAL Devices and Streams
Re: HAL Devices and Streams
- Subject: Re: HAL Devices and Streams
- From: <email@hidden>
- Date: Fri, 11 Jan 2002 16:44:18 -0600
I've noticed on OS X (up to 10.1.2 at least) QuickTime doesn't seem to have
the same access to multiple audio devices as OS 9, namely USB audio.
The list of available audio devices QuickTime API's FindNextComponent and
GetComponentInfo functions give is limited to FireWire DV, and two
variations of "HAL System". In contrast, under OS 9 with a USB audio device
connected (Griffin iMic), QuickTime has access to both "Built-In" and "USB
Audio", as it should.
Is this a limitation of the current QuickTime on OS X, or CoreAudio? What
will be done about this limitation in the future?
Thank you,
Jason
From CoreAudio-API list:
>
on 1/9/02 8:55 PM, Douglas Wright <email@hidden> wrote:
>
>
> I'm working on CoreAudio support in our applications here and I'm looking at
>
> the only multi-channel driver I've found, the MAudio Delta. The Delta 66 I
>
> have has 4 analog ins and outs and spdif in and out. It seems like it
>
> should be publishing one device with different streams for the different
>
> sorts of io, but instead it publishes several different devices each with
>
> only one stream. Is this the recommended way, or is this a kludge because
>
> the Sound pref panel does not let you choose different streams (yet?)
>
>
I'm not sure why they chose to implement the driver the way they did.
>
>
Possibly they wanted to work around the HAL's inability to allow the client
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to specify what streams they want to use. This would allow for better
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performance when the client isn't using every stream the device has at the
>
same time. This is potentially a big performance drain if the number of
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streams on the device is large and the number the client is using is small.
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>
Maybe they had other reasons. One thing, it proves how flexible the
>
architecture is. The driver has a great deal of leeway in how it presents
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it's device to the world.
>
>
> Any other multichannel core audio drivers available? Betas are good too...
>
>
Multi-channel USB Audio compliant devices should work for you.
>
>
--
>
>
Jeff Moore
>
Core Audio
>
Apple