Re: 5.1 Surround-to-stereo AU (Brian
Re: 5.1 Surround-to-stereo AU (Brian
- Subject: Re: 5.1 Surround-to-stereo AU (Brian
- From: Brian Willoughby <email@hidden>
- Date: Fri, 6 Feb 2009 14:06:46 -0800
Ernie,
Now that you've explained your goal more clearly, I don't think an AU
is appropriate. The advantage of AudioUnits is that you can use them
in applications that you have not written yourself. It is a plugin
format. Surround down mixing is already at a disadvantage at the
moment, here, because there are no hosts which know what to do with a
down-mixing plug-in.
In your case, you need to build a fake audio device driver.
Instructions for this can be found in the examples and in the
archives of this mailing list. The only difference in your case is
that your custom driver would publish surround formats instead of
stereo, thus fooling applications into thinking they had a surround
output device. Meanwhile, inside your driver, you would down-mix
those surround channels to stereo and pass them off to a real audio
driver which only supports stereo. You really have no need for an AU
in this scenario.
In other words, audio device drivers do not host AudioUnits. Only
applications host AUs (and maybe some future device drivers).
You may be confused because the default audio output device AudioUnit
provides the standard glue between an application and an audio output
device, however, the audio driver is not hosting this AU - it's
CoreAudio that is providing the link.
Brian Willoughby
Sound Consulting
On Feb 6, 2009, at 13:58, Ernest Burghardt wrote:
It seems like everything exists for what I would want to do, except
that I would want have an AU that would install for a specific device
and work for any application capable of playing audio, similar to a
driver, but the requirement of an AU host application seems to
complicate this idea.
I was hoping that an AU could take the place of doing the Mac version
of a filter driver that would install over the device's audio class
driver... I would love to wrong about this, so please feel free to
correct my understanding.
In the case that I can not use a host-less AU, may I ask for
recommendations for approaching this challenge?
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