Re: Getting the description of an AUHAL output node
Re: Getting the description of an AUHAL output node
- Subject: Re: Getting the description of an AUHAL output node
- From: William Stewart <email@hidden>
- Date: Mon, 24 Oct 2005 18:41:59 -0700
This is correct - is the AU initialized when you make this call? Have
you set it to a device?
AUHAL is a little weird in that most AUs you should only initialise
after you are ready to go... but because it has to deal with changing
device stuff, its generally best to just initialise this guy and
forget about it.... all of the format/device properties can be set on
this when it is initialised...
That's the only thing that comes to mind
Bill
On 24/10/2005, at 6:19 PM, Christopher Ashworth wrote:
Hi.
I have set up an AUGraph with two nodes: an AUHAL output node and a
matrix mixer. My goal is to mix multichannel sound files out to
arbitrary output devices. Most of the steps in this process work.
I can select any given output device and mix the channels of the
file out to the device.
When hooking up the mixer to the AUHAL node, however, I seem to be
missing something about how to discover the stream description of
the output device so that I may match my mixer to it. For example,
I have an Edirol FA-101 output device connected via Firewire that
has up to 10 mono channel outputs, but I am only able to mix out to
the first two channels.
This page:
http://developer.apple.com/technotes/tn2002/tn2091.html#FORMATS
indicates to me that the AUHAL output node should "flatten" the
output data stream into a single stream with 10 channels. I would
then expect to be able to make the following call to determine the
stream format:
// Get the stream description of the output device.
size = sizeof(desc);
err = AudioUnitGetProperty( outDeviceUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output, // output
scope,
0, // on the
output bus
&desc,
&size );
This, however, produces the error result
kAudioUnitErr_FormatNotSupported.
None too confident that I really understand the proper combination
of scopes and elements, I tried the other three, but even when I do
successfully get a stream description back, it only contains two
channels. i.e. I can only mix my sounds out to two of the ten
available channels on my device.
Help?
Christopher Ashworth
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