Re: Input gain query/set
Re: Input gain query/set
- Subject: Re: Input gain query/set
- From: Michael Thornburgh <email@hidden>
- Date: Tue, 16 Mar 2004 10:25:08 -0800
i found that the iSight will respond to
kAudioDevicePropertyVolumeScalar, at least, if it has IO cycles
running. i haven't tried setting "hog" mode, but i wouldn't be
surprised if that works too.
if you have my AudioMonitor app running, open two windows and set the
iSight as the input in both of them. scrub the volume control in one
of the windows and see nothing happens to the dB box in that window and
the other window's volume control doesn't track. then push the "Play
Through" button in one of the windows. as long as it's playing,
scrubbing the volume control should track between both windows and
affect the gain of the iSight.
AudioMonitor is setting kAudioDevicePropertyVolumeScalar, and receiving
notifications for and reading that property when the iSight is running
IO cycles.
-mike
On Mar 16, 2004, at 8:03 AM, Timothy J. Wood wrote:
The iSight seems to have a hardware input gain setting (or at least
a gain control shows up under System Prefs on 10.2.8 when it doesn't
show up for other input devices). But, I don't seem to be able to
query (let alone set) the value of this property.
I've tried the following properties on the AudioDeviceID for the
iSight:
kAudioDevicePropertyVolumeScalar
kAudioDevicePropertyVolumeRangeDecibels
kAudioDevicePropertyChannelNominalLineLevel
All of these return kAudioHardwareUnknownPropertyError when queried.
Am I missing something obvious?
Alternatively, is it just expected that I'd hook up the input to a
mixer AU and do the gain adjustment in software? This seems bad since
it loses any potential extra precision in samples that the device will
provide.
-tim
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