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POCannot get output volume from any audio devices from cocoa objective-c
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copied!<p>i'm trying to implement a volume control in a mac os x application. when i run code that loops over the audio devices installed in my macbook pro and queries their master volume (or individual channel volumes -- i've tried that too), i cannot get any results.</p> <p>here is the code i am running:</p> <pre><code>- (NSArray*)getAudioDevices { AudioObjectPropertyAddress propertyAddress = { kAudioHardwarePropertyDevices, kAudioObjectPropertyScopeGlobal, kAudioObjectPropertyElementMaster }; UInt32 dataSize = 0; OSStatus status = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize); if(kAudioHardwareNoError != status) { NSLog(@"Unable to get number of audio devices. Error: %d",status); return NULL; } UInt32 deviceCount = dataSize / sizeof(AudioDeviceID); AudioDeviceID *audioDevices = malloc(dataSize); status = AudioObjectGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize, audioDevices); if(kAudioHardwareNoError != status) { NSLog(@"AudioObjectGetPropertyData failed when getting device IDs. Error: %d",status); free(audioDevices), audioDevices = NULL; return NULL; } NSMutableArray* devices = [NSMutableArray array]; for(UInt32 i = 0; i < deviceCount; i++) { // Query device name CFStringRef deviceName = NULL; dataSize = sizeof(deviceName); propertyAddress.mSelector = kAudioDevicePropertyDeviceNameCFString; status = AudioObjectGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceName); if(kAudioHardwareNoError != status) { fprintf(stderr, "AudioObjectGetPropertyData (kAudioDevicePropertyDeviceNameCFString) failed: %i\n", status); continue; } // Query device output volume Float32 volume; propertyAddress.mSelector = kAudioHardwareServiceDeviceProperty_VirtualMasterVolume; status = AudioHardwareServiceHasProperty(audioDevices[i], &propertyAddress); if(status) { fprintf(stderr, "AudioObjectGetPropertyData (kAudioHardwareServiceDeviceProperty_VirtualMasterVolume) failed: %i\n", status); } else { dataSize = sizeof(volume); status = AudioObjectGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &volume); if (status) { // handle error } } NSLog(@"device found: %d - %@ || Vol: %f || status %i",audioDevices[i], deviceName, volume, status); [devices addObject:[NSNumber numberWithInt:audioDevices[i]]]; } free(audioDevices); return [NSArray arrayWithArray:devices]; } </code></pre> <p>and the output that i get from the log:</p> <pre><code>device found: 58 - Built-in Microphone || Vol: 0.000000 || status 2003332927 device found: 78 - Built-in Input || Vol: 0.000000 || status 2003332927 device found: 68 - Built-in Output || Vol: 0.000000 || status 2003332927 device found: 54 - Microsoft LifeCam VX-5000 || Vol: 0.000000 || status 2003332927 device found: 87 - Microsoft LifeChat LX-3000 || Vol: 0.000000 || status 2003332927 </code></pre> <p>i'm running OS X 10.7.3 / Xcode 4.3.2</p> <p>the volumes on the devices are not actually set at zero. can anyone tell me why i can't get any values?</p>

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