// static
bool BGMDeviceControlSync::SetVirtualMasterVolume(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32 inVolume)
{
// TODO: For me, setting the virtual master volume sets all the device's channels to the same volume, meaning you can't
// keep any channels quieter than the others. The expected behaviour is to scale the channel volumes
// proportionally. So to do this properly I think we'd have to store BGMDevice's previous volume and calculate
// each channel's new volume from its current volume and the distance between BGMDevice's old and new volumes.
//
// The docs kAudioHardwareServiceDeviceProperty_VirtualMasterVolume for say
// "If the device has individual channel volume controls, this property will apply to those identified by the
// device's preferred multi-channel layout (or preferred stereo pair if the device is stereo only). Note that
// this control maintains the relative balance between all the channels it affects.
// so I'm not sure why that's not working here. As a workaround we take the to device's (virtual master) balance
// before changing the volume and set it back after, but of course that'll only work for stereo devices.
bool didSetVolume = false;
AudioObjectPropertyAddress virtualMasterVolumeAddress =
{ kAudioHardwareServiceDeviceProperty_VirtualMasterVolume, inScope, kAudioObjectPropertyElementMaster };
bool hasVirtualMasterVolume = AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterVolumeAddress);
Boolean virtualMasterVolumeIsSettable;
OSStatus err = AudioHardwareServiceIsPropertySettable(inDevice.GetObjectID(), &virtualMasterVolumeAddress, &virtualMasterVolumeIsSettable);
virtualMasterVolumeIsSettable &= (err == kAudioServicesNoError);
if(hasVirtualMasterVolume && virtualMasterVolumeIsSettable)
{
// Not sure why, but setting the virtual master volume sets all channels to the same volume. As a workaround, we store
// the current balance here so we can reset it after setting the volume.
Float32 virtualMasterBalance;
bool didGetVirtualMasterBalance = GetVirtualMasterBalance(inDevice, inScope, virtualMasterBalance);
didSetVolume = kAudioServicesNoError == AHSSetPropertyData(inDevice.GetObjectID(), &virtualMasterVolumeAddress, sizeof(Float32), &inVolume);
// Reset the balance
AudioObjectPropertyAddress virtualMasterBalanceAddress =
{ kAudioHardwareServiceDeviceProperty_VirtualMasterBalance, inScope, kAudioObjectPropertyElementMaster };
if(didSetVolume && didGetVirtualMasterBalance && AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterBalanceAddress))
{
Boolean balanceIsSettable;
err = AudioHardwareServiceIsPropertySettable(inDevice.GetObjectID(), &virtualMasterBalanceAddress, &balanceIsSettable);
if(err == kAudioServicesNoError && balanceIsSettable)
{
AHSSetPropertyData(inDevice.GetObjectID(), &virtualMasterBalanceAddress, sizeof(Float32), &virtualMasterBalance);
}
}
}
return didSetVolume;
}
bool canSetVolume()
{
Boolean isSettable = NO;
return AudioHardwareServiceIsPropertySettable (outputDeviceID, &addr, &isSettable) == noErr
&& isSettable;
}
// setting system volume. Mutes if under threshhold.
// Courtesy: https://gist.github.com/atr000/205140
int setVolume(float newVolume) {
if (newVolume < 0.0 || newVolume > 1.0) {
fprintf(stderr, "ERROR: Requested volume out of range (%.2f)\n", newVolume);
return 1;
}
// get output device
UInt32 propertySize = 0;
OSStatus status = noErr;
AudioObjectPropertyAddress propertyAOPA;
propertyAOPA.mElement = kAudioObjectPropertyElementMaster;
propertyAOPA.mScope = kAudioDevicePropertyScopeOutput;
if (newVolume < 0.001) {
propertyAOPA.mSelector = kAudioDevicePropertyMute;
} else {
propertyAOPA.mSelector = kAudioHardwareServiceDeviceProperty_VirtualMasterVolume;
}
AudioDeviceID outputDeviceID = defaultOutputDeviceID();
if (outputDeviceID == kAudioObjectUnknown) {
fprintf(stderr, "ERROR: Unknown device\n");
return 2;
}
if (!AudioHardwareServiceHasProperty(outputDeviceID, &propertyAOPA)) {
fprintf(stderr, "ERROR: Device 0x%0x does not support volume control\n", outputDeviceID);
return 3;
}
Boolean canSetVolume = false;
status = AudioHardwareServiceIsPropertySettable(outputDeviceID, &propertyAOPA, &canSetVolume);
if (status || !canSetVolume) {
fprintf(stderr, "ERROR: Device 0x%0x does not support volume control\n", outputDeviceID);
return 4;
}
if (propertyAOPA.mSelector == kAudioDevicePropertyMute) {
propertySize = sizeof(UInt32);
UInt32 mute = 1;
status = AudioHardwareServiceSetPropertyData(outputDeviceID, &propertyAOPA, 0, NULL, propertySize, &mute);
} else {
propertySize = sizeof(Float32);
status = AudioHardwareServiceSetPropertyData(outputDeviceID, &propertyAOPA, 0, NULL, propertySize, &newVolume);
if (status) {
fprintf(stderr, "ERROR: Unable to set volume for device 0x%0x\n", outputDeviceID);
return 5;
}
// make sure we're not muted
propertyAOPA.mSelector = kAudioDevicePropertyMute;
propertySize = sizeof(UInt32);
UInt32 mute = 0;
if (!AudioHardwareServiceHasProperty(outputDeviceID, &propertyAOPA)) {
fprintf(stderr, "ERROR: Device 0x%0x does not support muting\n", outputDeviceID);
return 6;
}
Boolean canSetMute = false;
status = AudioHardwareServiceIsPropertySettable(outputDeviceID, &propertyAOPA, &canSetMute);
if (status || !canSetMute) {
fprintf(stderr, "ERROR: Device 0x%0x does not support muting\n", outputDeviceID);
return 7;
}
status = AudioHardwareServiceSetPropertyData(outputDeviceID, &propertyAOPA, 0, NULL, propertySize, &mute);
}
if (status) {
fprintf(stderr, "ERROR: Unable to set volume for device 0x%0x\n", outputDeviceID);
return 8;
}
return 0;
}