Re: how to tell if you can change a data source under program control
Re: how to tell if you can change a data source under program control
- Subject: Re: how to tell if you can change a data source under program control
- From: Jeff Moore <email@hidden>
- Date: Fri, 20 Sep 2002 11:09:02 -0700
Data Source controls are totally supported on a per stream basis. The
HAL has explicit support for this. The HAL looks for a control
attached to the IOAudioStream object with a channel of 0. It uses this
control for the master on that stream.
This is exactly why the HAL makes such a big deal about the difference
between device channel 0 and stream channel 0. They refer to different
places for attaching controls in the driver.
On Thursday, September 19, 2002, at 06:13 PM, B.J. Buchalter wrote:
i see now that to get the current source you must use the
master channel of the device. that makes more sense in the context
of the reply i actually got to the bug report, and, i suppose, makes
sense with respect to the actual device.
i can imagine there being devices with per-channel or per-stream
independent source selectors. is that supported/possible with
the HAL and the IOAudio family, or is it only possible to have
one source per direction per device (on the device master channel)?
It appears that CoreAudio does not support this yet. It is something
that we
could actually use for our device(s) -- most of our channels have a
number
of sources or psuedo sources that currently can only be controlled by
our
console App. It would be cool to be able to export that control to CA
clients without having to resort to some set of private properties. So
I
second Mike's motion -- it would be good to have source selectors on a
per
channel (or at least per stream) basis.
Best regards,
B.J. Buchalter
Metric Halo
M/S 601 - Building 8
Castle Point Campus
Castle Point, NY 12511-0601 USA
tel +1 845 831-8600
fax +1 603 250-2451
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--
Jeff Moore
Core Audio
Apple
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