Re: Device Sync (was Re: Multiple HALAOUs don't get along?)
Re: Device Sync (was Re: Multiple HALAOUs don't get along?)
- Subject: Re: Device Sync (was Re: Multiple HALAOUs don't get along?)
- From: William Stewart <email@hidden>
- Date: Wed, 16 Jun 2004 16:53:23 -0700
On 16/06/2004, at 4:33 PM, David Duncan wrote:
>
On Jun 16, 2004, at 05:25 PM, William Stewart wrote:
>
>
> No - As Robert stated, he's doing this just fine.
>
>
I think the key difference here is that Robert is gluing the 2nd AUHAL
>
into the AUGraph (because you can only have one output unit in an
>
AUGraph). Since Chilton is not using AUGraph, he is simply using the
>
connection properties to paste the AUs together via the
>
kAudioUnitProperty_MakeConnection property. Thus OutputUnit pulls from
>
FilterUnit pulls from InputUnit (where InputUnit & OutputUnit are
>
both AUHAL units and FilterUnit is an effect unit). This specific
>
configuration doesn't appear to work. The same exact code works just
>
fine if you have the OutputUnit pull from the FilterUnit pull from the
>
OutputUnit. Somehow this seems like a bug to me.
No - basic misunderstanding.
If you have one (or two) AUHAL units pointing at the same device, then
you can make a connection between them just fine.
If you have one AUHAL looking at one device, and a second one at
another device then you can't. Why? Because each AUHAL is going to run
in its own thread (the I/O Proc of the device). The only time you can
call AudioUnitRender - for input - is in the ****same**** thread as its
I/O Proc. That is why you have this property to notify you that input
has arrived... when you get that notification you call AudioUnitRender
(you are running in the I/O proc for that device when this notification
is called).
You can't connect two up from different devices, because the output
side is going to call in its I/O proc - if its connected it calls for
input, but you aren't on the right thread (you're on the thread for the
output device, not the input device) - so you don't get anything back.
I think this is explained in the tech note - if its not, then please
let us know and we'll update it.
Bill - I hear the sound of a thousand feet chasing me :-)
>
>
If you need more information then maybe Chilton can probably post some
>
source code.
>
>
> We're working up an extension to the existing sample code and will
>
> have
>
> that available as soon as we can.
>
>
Great!
>
--
>
Reality is what, when you stop believing in it, doesn't go away.
>
Failure is not an option. It is a privilege reserved for those who try.
>
>
David Duncan
>
>
--
mailto:email@hidden
tel: +1 408 974 4056
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