CoreAudio: how to get / set the volume of a system warning, as opposed to the volume of a device

Question

I searched the documentation, the on and off mailing lists for several days, but cannot find the answer to this question.

I have an OS X application that, among other things, queries available hardware devices and their current volumes using kAudioDevicePropertyVolumeScalar and friends.

What I want to do is get and set -alert-volume (?) For the system output device represented by kAudioHardwarePropertyDefaultSystemOutputDevice, not the volume of these devices.

To understand from my limited understanding, this is a volume parameter that users can configure in the System Preferences under the "Play Sound Effects Through" section.

Searching the lists of coreaudio-api, I was able to calculate that this volume parameter is not a property of the device, but some derived value, but I'm at a dead end, where is it from here.

Any help would be greatly appreciated.

Answer 1

I'm not sure if you really have a requirement to read it through CoreAudio, but the following works just fine:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [defaults addSuiteNamed:@"com.apple.systemsound"]; NSLog(@"%f", [defaults floatForKey:@"com.apple.sound.beep.volume"]); 

Although this may change with updating the operating system, as the settings are saved in ~/Library/Preferences/com.apple.systemsound.plist .