Re: HAL Output IOProc and multiple AudioBuffers
Re: HAL Output IOProc and multiple AudioBuffers
- Subject: Re: HAL Output IOProc and multiple AudioBuffers
- From: William Stewart <email@hidden>
- Date: Tue, 6 Jul 2004 16:43:43 -0700
And for clarity from Jeff's post:
On 06/07/2004, at 12:22 PM, Jeff Moore wrote:
>
The right thing to do with streams you don't wish to do IO with is to
>
disable them for your IOProc using
>
kAudioDevicePropertyIOProcStreamUsage.
This is what AUHAL does for you whenever there is a mismatch between
the number of channels of the device and the number of channels of the
client - it uses the channel map you set as further information to
decide which streams are not in use at any particular time.
Bill
On 06/07/2004, at 12:52 PM, William Stewart wrote:
>
Neither.
>
>
You should tell the AUHAL unit how many channels that you want to give
>
it.
>
>
It will then call you for just that many channels (for example, 2
>
channels).
>
>
Then you can use the channel map property to direct which of the
>
multitude of channels of the device, your 2 channels should go too.
>
>
There have been a number of discussions on the channel map property on
>
the list recently, and there's some docs on it in the core audio
>
documentation
>
>
Bill
>
>
On 06/07/2004, at 6:18 AM, Sven Behne Listen wrote:
>
>
> Hi all!
>
>
>
> I'm having a question regarding the HAL output IOProc in cases where
>
> an
>
> AudioDevice has an AudioBufferList with more than one AudioBuffer
>
> (like
>
> a MOTU 828 with 8 analog and 2 digital outs).
>
>
>
> Supposed, I'm having only 8 channels and don't want any output on the
>
> additional 2 digital channels, is it allright to set the mDataByteSize
>
> field of the corresponding buffer to 0?
>
>
>
> Or - if that's not within specs - am I safe to assume, that the
>
> AudioBuffer's data will be zero the first time the IOProc is called
>
> and
>
> I don't have to zero the buffer every time the IOProc is called?
>
>
>
> Best regards,
>
>
>
> Sven
>
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