Re: Sound Level
Re: Sound Level
- Subject: Re: Sound Level
- From: Shaun Wexler <email@hidden>
- Date: Mon, 7 Apr 2003 18:14:19 -0700
On Monday, April 7, 2003, at 05:46 AM, Lorenzo wrote:
Hi, how to control the sound level of the Mac, and
ho to control the sound level of my Cocoa application?
NSSound is not the answer. So please, what?
Use some simple CoreAudio HAL calls:
UInt32 direction = 0; // 0 = output, 1 = input
UInt32 left = 0, right = 1;
UInt32 deviceID;
UInt32 propertySize;
UInt32 stereoChannels[2];
float channelVolume[2];
OSStatus status;
// get the deviceID for the default system output device
propertySize = sizeof(deviceID);
status =
AudioHardwareGetProperty(kAudioHardwarePropertyDefaultSystemOutputDevice
, & propertySize, &deviceID);
// get channel numbers, so you know which channels are left and right
propertySize = sizeof(stereoChannels);
status = AudioDeviceGetProperty(deviceID, NULL, direction,
kAudioDevicePropertyPreferredChannelsForStereo, &propertySize,
&stereoChannels);
// read the current volume scalar settings [0..1]
propertySize = sizeof(float);
status = AudioDeviceGetProperty(deviceID, stereoChannels[left],
direction, kAudioDevicePropertyVolumeScalar, &propertySize,
&channelVolume[left]);
status = AudioDeviceGetProperty(deviceID, stereoChannels[right],
direction, kAudioDevicePropertyVolumeScalar, &propertySize,
&channelVolume[right]);
// adjust the volumes to taste (example)
channelVolume[left] *= 0.50f; // set left output volume to 50% of
current value
channelVolume[right] *= 0.50f; // set right output volume to 50% of
current value
// apply the new settings
//propertySize = sizeof(float); // if needed
status = AudioDeviceSetProperty(deviceID, stereoChannels[left],
direction, kAudioDevicePropertyVolumeScalar, propertySize,
&channelVolume[left]);
status = AudioDeviceSetProperty(deviceID, stereoChannels[right],
direction, kAudioDevicePropertyVolumeScalar, propertySize,
&channelVolume[right]);
Disclaimer: normal result status/error checking deleted for brevity,
written in Mail.app, untested. Enjoy!
--
Shaun Wexler
MacFOH
http://www.macfoh.com
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| References: | |
| | >Sound Level (From: Lorenzo <email@hidden>) |