Re: efficient device channel enabling - was Re: fIsMixable
Re: efficient device channel enabling - was Re: fIsMixable
- Subject: Re: efficient device channel enabling - was Re: fIsMixable
- From: Kurt Bigler <email@hidden>
- Date: Tue, 10 Feb 2004 16:59:47 -0800
on 2/3/04 8:35 AM, Doug Wyatt <email@hidden> wrote:
>
On Feb 2, 2004, at 19:35, Kurt Bigler wrote:
>
> Reviving an old topic...
>
>
>
>
>
> on 6/18/03 12:02 PM, Jeff Moore <email@hidden> wrote:
>
>
>
>> To date, there haven't been too many apps that have taken advantage of
>
>> the ability to enable and disable streams. I'm not entirely sure why
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>> that is, but at least part of that is our fault. We have not fully
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>> implemented that support in the HAL Audio Units or in the Sound
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>> Manager. This will be fixed as time progresses.
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>
>
> I am about to revisit the issue of implementing stream enables in my
>
> application. How has support for stream enables changed since you
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> posted
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> the above reply last year?
>
>
>
> Do I have to abandon audio output units and use the HAL directly in
>
> order to
>
> use stream enables? Or do I just add some HAL calls to do the stream
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> eanbling and trust that audio output units will behave intelligently in
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> relation to devices that have had some streams disabled via the HAL
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> API?
>
>
The audio (input/)output units present all of a device's streams as a
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single bus with N channels (where N is the sum of the number of
>
channels in each stream). You set an *input* format to the output unit
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(set on element 0 in the input scope), and you can map your input
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channels to the hardware channels using the output unit's channel map
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property. The output units will then dynamically enable/disable the
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hardware streams according to which ones are being addressed.
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>
This is as of Panther / QT 6.4.
Thanks, but I don't get it. What if inputs are not being used? You are
talking about output stream enabling being affected by input channel
mapping? How is is that the output stream enabling configuration is even
deterministic based on input? I might want to use the outputs in any old
way, regardless of input mapping. ???
Assuming I can get hold of the address of the HAL ioproc that get used
implicitly when I use an output audio unit, what happens if I enable/disable
output streams on that ioproc? How does an output AU that is using the
device handle this?
Thanks,
Kurt Bigler
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