Re: Multiple output devices under CoreAudio with Quicktime
Re: Multiple output devices under CoreAudio with Quicktime
- Subject: Re: Multiple output devices under CoreAudio with Quicktime
- From: Dave Addey <email@hidden>
- Date: Fri, 20 Jun 2003 17:13:43 +0100
Hi,
A few months ago, Jeff posted the reply below to a problem I was having, and
it got everything working for me using multiple output devices under OS X
via QuickTime. I found that this solution worked on all versions of OS X
with QuickTime 6 installed - not just OS X 10.2.
However, users of my application are being demanding, and I have a further
question...
I can now access hardware output devices, via QuickTime, using the sdev
approach mentioned below. However, if the hardware output device has (for
example) 8 sets of stereo outputs, the corresponding sdev only points to one
of these stereo outputs. So, I can output audio to the device, but only
through one of its stereo outputs.
My question is this: is there a way (via this QuickTime / Sound Manager
approach) to access the multiple channels (or streams) of an output device
under OS X? Or if not, where should I start for finding and outputting
sound to multiple channels of one device? And will this mean moving all of
my other code away from QuickTime and SoundManager into some new CoreAudio
world?
Sorry for the basic question, but I'm struggling to get started with this!
Thanks in advance,
Dave.
------------------------------------
Dave Addey
email@hidden
DJ-1800
Complete DJ solution for the Mac
http://www.dj1800.com/
Support and pre-release forums:
http://dj1800.myforums.net/
On 14/4/03 7:51 pm, "Jeff Moore" <email@hidden> wrote:
>
You don't say what version of the system you are using, but in 10.2,
>
the Sound Manager was updated to create sdevs for all of the output
>
devices in the HAL. The catch is that you need to be sure you have
>
initialized the Sound Manager prior to trying to iterate through the
>
sdevs with FindNextComponent(). You can call something like
>
SndManagerStatus, to accomplish this.
>
>
On Monday, April 14, 2003, at 01:46 AM, Dave Addey wrote:
>
>
> Hi,
>
>
>
> I'm just about to start porting some Carbon Audio code to take
>
> advantage of
>
> CoreAudio, and I'm really struggling to get a grip on the best
>
> approach to
>
> take... Any help much appreciated! Questions below, after a brief
>
> explanation:
>
>
>
> I've written a Mac DJ application called DJ-1800 (see
>
> http://www.dj1800.com/) using REALbasic. It allows multiple output
>
> devices
>
> for DJing, and emulates 4 DJ-style "CD players" for controlling MP3
>
> playback.
>
>
>
> I'm currently working with a QuickTime movieplayer, which contains a
>
> movie
>
> with 3 MP3 tracks (all identical). I'm using
>
> MediaSetSoundOutputComponent
>
> from the Quicktime API to assign a different output device to each
>
> channel.
>
> (This allows my DJ application to play a song through a master device
>
> and a
>
> cue device at the same time).
>
>
>
> Via Quicktime, I'm looking for all OutputComponents of type 'sdev',
>
> but on
>
> OS X there are only the two - Mac OS Audio HAL, and Mac OS Audio HAL
>
> (system) - corresponding to the system out and the system alerts out
>
> respectively. I'm using these two to allow users to use two audio
>
> devices
>
> (typical their built-in device, and an iMic or similar) - one for
>
> headphones, and one for master oputput.
>
>
>
> This works to a point, on OS 9 and X using Quicktime. However, I have
>
> two
>
> major problems:
>
>
>
> 1) Users would like to be able to use more than two devices (e.g. an
>
> M-Audio
>
> Delta 1010lt soundcard (with 8 outputs)) to assign four different
>
> output
>
> devices (one to each CD player) - not possible with the current
>
> approach. I
>
> believe I need to use CoreAudio to access these extra "devices" under
>
> Mac OS
>
> X. How can I find all available output devices under CoreAudio, and
>
> assign
>
> them to the tracks of a QuickTime movie?
>
>
>
> 2) Ideally, I want to be able to assign multiple output devices to one
>
> track
>
> in a QT movie, rather than the clunky multi-track approach I'm having
>
> to use
>
> currently. Is this possible under CoreAudio?
>
>
>
> As I say, any help much appreciated...
>
>
>
> Thanks,
>
>
>
> Dave.
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