AudioObjectGetPropertyData to get a list of input devices

Question

How do I utilize AudioObjectGetPropertyData in OS X to retrieve a list of the system\'s input devices? I currently have the following dummy code for retrieving

Answer 1

I have slightly modified the code submitted by "sbooth" to print all the input devices along with the no. of buffers for each device and no. of channels for each buffer.

CFArrayRef CreateInputDeviceArray()
{
    AudioObjectPropertyAddress propertyAddress = {
        kAudioHardwarePropertyDevices,
        kAudioObjectPropertyScopeGlobal,
        kAudioObjectPropertyElementMaster
    };

    UInt32 dataSize = 0;
    OSStatus status = AudioHardwareServiceGetPropertyDataSize(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize);
    if(kAudioHardwareNoError != status) {
        fprintf(stderr, "AudioObjectGetPropertyDataSize (kAudioHardwarePropertyDevices) failed: %i\n", status);
        return NULL;
    }

    UInt32 deviceCount = (UInt32)(dataSize / sizeof(AudioDeviceID));

    AudioDeviceID *audioDevices = (AudioDeviceID *)(malloc(dataSize));
    if(NULL == audioDevices) {
        fputs("Unable to allocate memory", stderr);
        return NULL;
    }

    status = AudioHardwareServiceGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize, audioDevices);
    if(kAudioHardwareNoError != status) {
        fprintf(stderr, "AudioObjectGetPropertyData (kAudioHardwarePropertyDevices) failed: %i\n", status);
        free(audioDevices), audioDevices = NULL;
        return NULL;
    }

    CFMutableArrayRef inputDeviceArray = CFArrayCreateMutable(kCFAllocatorDefault, deviceCount, &kCFTypeArrayCallBacks);
    if(NULL == inputDeviceArray) {
        fputs("CFArrayCreateMutable failed", stderr);
        free(audioDevices), audioDevices = NULL;
        return NULL;
    }

    // Iterate through all the devices and determine which are input-capable
    propertyAddress.mScope = kAudioDevicePropertyScopeInput;
    for(UInt32 i = 0; i < deviceCount; ++i) {
        // Query device UID
        CFStringRef deviceUID = NULL;
        dataSize = sizeof(deviceUID);
        propertyAddress.mSelector = kAudioDevicePropertyDeviceUID;
        status = AudioHardwareServiceGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceUID);
        if(kAudioHardwareNoError != status) {
            fprintf(stderr, "AudioObjectGetPropertyData (kAudioDevicePropertyDeviceUID) failed: %i\n", status);
            continue;
        }

        // Query device name
        CFStringRef deviceName = NULL;
        dataSize = sizeof(deviceName);
        propertyAddress.mSelector = kAudioDevicePropertyDeviceNameCFString;
        status = AudioHardwareServiceGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceName);
        if(kAudioHardwareNoError != status) {
            fprintf(stderr, "AudioObjectGetPropertyData (kAudioDevicePropertyDeviceNameCFString) failed: %i\n", status);
            continue;
        }

        // Query device manufacturer
        CFStringRef deviceManufacturer = NULL;
        dataSize = sizeof(deviceManufacturer);
        propertyAddress.mSelector = kAudioDevicePropertyDeviceManufacturerCFString;
        status = AudioHardwareServiceGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, &deviceManufacturer);
        if(kAudioHardwareNoError != status) {
            fprintf(stderr, "AudioObjectGetPropertyData (kAudioDevicePropertyDeviceManufacturerCFString) failed: %i\n", status);
            continue;
        }

        // Determine if the device is an input device (it is an input device if it has input channels)
        dataSize = 0;
        propertyAddress.mSelector = kAudioDevicePropertyStreamConfiguration;
        status = AudioHardwareServiceGetPropertyDataSize(audioDevices[i], &propertyAddress, 0, NULL, &dataSize);
        if(kAudioHardwareNoError != status) {
            fprintf(stderr, "AudioObjectGetPropertyDataSize (kAudioDevicePropertyStreamConfiguration) failed: %i\n", status);
            continue;
        }

        AudioBufferList *bufferList = (AudioBufferList *)(malloc(dataSize));
        if(NULL == bufferList) {
            fputs("Unable to allocate memory", stderr);
            break;
        }

        status = AudioHardwareServiceGetPropertyData(audioDevices[i], &propertyAddress, 0, NULL, &dataSize, bufferList);
        if(kAudioHardwareNoError != status || 0 == bufferList->mNumberBuffers) {
            if(kAudioHardwareNoError != status)
                fprintf(stderr, "AudioObjectGetPropertyData (kAudioDevicePropertyStreamConfiguration) failed: %i\n", status);
            free(bufferList), bufferList = NULL;
            continue;
        }
        UInt32 numBuffers = bufferList->mNumberBuffers;

        printf("\n\ndeviceUID:%s \tdeviceName: %s\ndeviceManufacturer: %s\t#Buffers:%d", \
               CFStringGetCStringPtr(deviceUID, kCFStringEncodingMacRoman),\
               CFStringGetCStringPtr(deviceName, kCFStringEncodingMacRoman), \
               CFStringGetCStringPtr(deviceManufacturer, kCFStringEncodingMacRoman), \
               numBuffers
               );
        for (UInt8 j = 0; j < numBuffers; j++) {
            AudioBuffer ab = bufferList->mBuffers[j];
            printf("\n#Channels: %d DataByteSize: %d", ab.mNumberChannels, ab.mDataByteSize);
        }

        free(bufferList), bufferList = NULL;

        // Add a dictionary for this device to the array of input devices
        CFStringRef keys    []  = { CFSTR("deviceUID"),     CFSTR("deviceName"),    CFSTR("deviceManufacturer") };
        CFStringRef values  []  = { deviceUID,              deviceName,             deviceManufacturer };



        CFDictionaryRef deviceDictionary = CFDictionaryCreate(kCFAllocatorDefault,
                                                              (const void **)(keys),
                                                              (const void **)(values),
                                                              3,
                                                              &kCFTypeDictionaryKeyCallBacks,
                                                              &kCFTypeDictionaryValueCallBacks);


        CFArrayAppendValue(inputDeviceArray, deviceDictionary);

        CFRelease(deviceDictionary), deviceDictionary = NULL;
    }

    free(audioDevices), audioDevices = NULL;

    // Return a non-mutable copy of the array
    CFArrayRef copy = CFArrayCreateCopy(kCFAllocatorDefault, inputDeviceArray);
    CFRelease(inputDeviceArray), inputDeviceArray = NULL;

    return copy;
}