Re: What is the common endpoint for audio from applications?
Re: What is the common endpoint for audio from applications?
- Subject: Re: What is the common endpoint for audio from applications?
- From: Jeff Moore <email@hidden>
- Date: Tue, 15 Aug 2006 15:29:54 -0700
On Aug 15, 2006, at 3:19 PM, Nick Hebner wrote:
I am new to the core audio api and mac programming in general. I am
looking at writing an application
for which I need to have access to all audio streams on the system.
My initial idea was to write it using
core audio api's to enumerate all streams on all devices, and fiddle
with these streams.
OK. I'm with you so far. I'll just point out that in /Developer/
Examples/CoreAudio/HAL/HALLab, you'll find a project that builds an
app that puts a GUI on all the HAL's properties. Makes for an easy way
to explore the hardware.
I wrote a test
program to see if this would work, it was indicating that there was
only one stream on my one output device,
even when I was playing audio with iTunes and GarageBand.
This is correct. You are enumerating the output streams of the
hardware and for our built-in hardware, there is only one.
Am I able to access streams from other applications
The short answer is no. There are no APIs for directly accessing the
audio data coming out of other processes.
The long answer involves writing a fake device using the HAL's user-
land driver plug-in API or some kind of in-kernel reflector.
, and if so how?
You can also just use something like Jack, which uses the user-land
approach. SoundFlower or the lowly AudioReflectorDriver in our SDK do
the job of being a fake device by being an in-kernel reflector.
Are these programs using other audio frameworks such as quicktime,
etc?
No. They are all using Core Audio in one fashion or another.
How do all of these frameworks access the same audio hardware, do
they use core audio at their heart, or is
it something else?
Audio device sharing is just how things have always worked on the Mac,
even before X came about.
--
Jeff Moore
Core Audio
Apple
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