Re: kAudioHardwarePropertyDeviceForUID ???
Re: kAudioHardwarePropertyDeviceForUID ???
- Subject: Re: kAudioHardwarePropertyDeviceForUID ???
- From: Michael Thornburgh <email@hidden>
- Date: Fri, 20 Sep 2002 10:53:21 -0700
On Friday, September 20, 2002, at 09:31 AM, Baron wrote:
note: If you are using a USB device for example, it will have a
different
UID for each USB port in which it is connected.
this is only true if the usb audio device doesn't have a serial number.
if it does have a serial number, that's used instead of its usb position
ID/address.
that's theoretically what you really want, so that the device UID is
actually
associated with that particular device no matter where you plug it in.
so
that if you take a sharpie and write a big "A" on one device and a "B"
on
another one of the same kind of device, and want to plug particular
stuff
into "A" and other particular stuff into "B", that'll do the expected
thing.
unfortunately, some usb audio devices (like the kinda old griffin imics
i have --
maybe john can tell us if this is no longer the case with more recent
imics) seem to
report the same serial number (042067). this is a problem because the
device
has a serial number, so that's used instead of the device address, but
then a second device plugged in will end up with exactly the same UID
being
constructed, so the HAL can't tell them apart. only one of them will
end
up working -- probably the most recently plugged in one. i'm told by a
friend who does USB development at SCO that the
non-unique-serial-number problem
is pretty widespread among manufacturers of all kinds of usb things.
i played around with having a blacklist of device/manufacturer/serial
numbers
in the usb audio driver, so that the usb address could be substituted
for
non-unique-serial-number devices. maintaining that might be annoying,
though,
but it was neat to have two working imics on my system at once. :)
i didn't pursue it because some system services (default audio devices)
seemed
to be using the device name instead of the UID, so depending on whether
i'd plugged/unplugged anything, the wrong device was getting selected
for
my default in or out. (this was 10.1 -- i haven't come back to this
since
10.2)
-mike
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