Re: Multiple Sound Devices
Re: Multiple Sound Devices
- Subject: Re: Multiple Sound Devices
- From: Mark Thomas <email@hidden>
- Date: Tue, 12 Feb 2002 20:33:08 +0000
- Organization: Coderus Ltd
Hi Bill,
I'm trying to somehow work this on MacOS 9.x. I have included Laurent
email below
Thanks
Mark.
Hi,
>
I may sound "pushy" (but after all this is part of my role :-)), but why
>
don't you switch to CoreAudio?
No worries :-)
I'm switching to CoreAudio, but I still have to support MacOS 9.x, for at
least another 12-18 months, Sorry but I'm not completely willing to put all
my eggs in MacOS-X just yet. As there are a lot of machines still out there
which wouldn't be MacOS-X compatible.
>
>
The logic of the management of USB external speakers on OS 9 is made in
>
the Apple Audio Extension, that create and more generally "manipulate"
>
the output component that can be used by the Sound Manager. The only
>
point of access to this is through the 'sdev' output component(s). There
>
will never be other API's, hack, code path or so on to access the
>
inside of Apple Audio Extension and deal with the management of pugged
>
device. On OS X the Carbon Sound Manager sits on top of CoreAudio, so
>
you will have more flexibilty using the HAL directly.
>
Hmmmm, any idea of where some docs on 'sdev', as I guess I can count the
number of 'sdev', and ask them for some information, I guess there are docs
for 'sdev' somewhere, but I'll never be able to switch to particular
speaker, because of this.
Also what are these SoundComponent APIs in <Sound.H>, are these output
components info functions, as I cannot find any docs on them or sample code,
is there any available I can have. ???
Also what are SPBxxxxx funcations used for ???.
>
One of the goal of CoreAudio was precisely to "open this component" and
>
give access to a representation of the real hardware (and at the same
>
time to deal for you with the problem of a kernel/user transition of
>
data) , this, with a set of API's more modern and suited to the
>
evolution of the audio world.
>
I'm glad to see that it straight forward here.
>
Laurent
>
>
Laurent Cerveau
>
Applications Division
>
Apple Computer Inc.
>
email@hidden
>
Thanks
Mark.
>
on 12/2/02 1:36 AM, Mark Thomas wrote:
>
>
> Hi,
>
> Its not using mono or stereo output, but if I have some USB speakers
>
> plugged in, I want to send different sound data to the USB speakers, and
>
> some other sound data to the internal speakers, as well as know that I have
>
> these sound output devices, using the Sound Manager.
>
>
>
> When you are in the Sound Control Panel, it seems to known about the
>
> different output devices. Any Ideas how it does this ???.
>
>
It uses the CoreAudio APIs to iterate through the list of currently
>
available AudioDevices (this is described in AudioHardware.h)
>
>
Bill
>
>
>
> Thanks
>
> Mark.
>
>
>
>> on 2/11/02 8:03 AM, Mark Thomas <email@hidden> wrote:
>
>>
>
>>> Hi,
>
>>> Sorry for asking a Sound Manager question, but there doesn't seem to be
>
>>> good one for this, and I guess this is an easy question for you guys :-).
>
>>>
>
>>> My application presently uses the Sound Manager API, it creates its Sound
>
>>> Channels, and everything works great, and I get sound out of all the
>
>>> speakers attached.
>
>>>
>
>>> But thought wouldn't it be cool, to have different sounds out of the
>
>>> different speakers.
>
>>>
>
>>> Is there a way to find out how many speakers devices you have attached,
>
>>> and then how to send the data to the different devices. I can see how you
>
>>> do
>
>>> this with Core Audio, but the Sound Manager api's seem hidden away, also
>
>>> any
>
>>> sample code would be great.
>
>>
>
>>
>
>> I once did performance test comparing stereo output to mono output with
>
>> Sound Manager. There was no difference. So why not just output stereo all
>
>> the time. In a mono situation the two channels will be mixed (averaged)
>
>> automatically, and this apparently causes no performance penalty.
>
>>
>
>> Saying this makes me wonder whether in fact the mono situation actually
>
>> causes only the 1st (left?) channel info to be used. I have long had the
>
>> impression that this is not the case, although I can't say now where I
>
>> learned that. In any case it would be easy to verify that this is not a
>
>> problem.
>
>>
>
>> -Kurt Bigler (not an apple employee)
>
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