如何获得当前音量[重复]

Posted 2023-02-25

【中文标题】如何获得当前音量[重复]

【英文标题】：How to get Current Volume Level [duplicate]

【发布时间】：2013-02-27 16:40:56

【问题描述】：

我正在开发 10.8

这是获取当前扬声器音量的代码，

-(float)getVolume

    float volume = 0.0;

    UInt32 thePropSize = sizeof(volume);

    AudioDeviceID devId = [self GetOutputAudioDevice];

    AudioObjectPropertyAddress thePropertyAddress =  kAudioDevicePropertyVolumeScalar, kAudioDevicePropertyScopeOutput, kAudioObjectPropertyElementMaster ;


    if(AudioObjectHasProperty(devId, &thePropertyAddress))
        AudioObjectGetPropertyData(devId, &thePropertyAddress, 0, NULL, &thePropSize, &volume);
    else
        printf(" doesn't have property to get the volume");
    

    return volume;

函数 AudioObjectHasProperty 无法获取 Current Vol 属性，不知道出了什么问题，

这是选择默认输出设备的代码，

-(AudioDeviceID)GetOutputAudioDevice

    OSStatus err;
    AudioDeviceID device = 0;
    UInt32 size = sizeof(AudioDeviceID);
    AudioObjectPropertyAddress address = 
        kAudioHardwarePropertyDefaultOutputDevice,
        kAudioObjectPropertyScopeGlobal,
        kAudioObjectPropertyElementMaster
    ;

    err = AudioObjectGetPropertyData(kAudioObjectSystemObject,
                                     &address,
                                     0,
                                     NULL,
                                     &size,
                                     &device);
    if (err)
    
        NSLog(@"could not get default audio output device");
    

    return device;

【参考方案1】：

有两种选择。第一步是确定您想要什么设备并获取其 ID。假设默认输出设备，代码将如下所示：

AudioObjectPropertyAddress propertyAddress =  
    kAudioHardwarePropertyDefaultOutputDevice, 
    kAudioObjectPropertyScopeGlobal, 
    kAudioObjectPropertyElementMaster 
;

AudioDeviceID deviceID;
UInt32 dataSize = sizeof(deviceID);
OSStatus result = AudioObjectGetPropertyData(kAudioObjectSystemObject, &propertyAddress, 0, NULL, &dataSize, &deviceID);

if(kAudioHardwareNoError != result)
    // Handle the error
Next, you can use the kAudioHardwareServiceDeviceProperty_VirtualMasterVolume property to get the device's virtual master volume:

AudioObjectPropertyAddress propertyAddress =  
    kAudioHardwareServiceDeviceProperty_VirtualMasterVolume, 
    kAudioDevicePropertyScopeOutput,
    kAudioObjectPropertyElementMaster 
;

if(!AudioHardwareServiceHasProperty(deviceID, &propertyAddress))
    // An error occurred

Float32 volume;
UInt32 dataSize = sizeof(volume);
OSStatus result = AudioHardwareServiceGetPropertyData(deviceID, &propertyAddress, 0, NULL, &dataSize, &volume);

if(kAudioHardwareNoError != result)
    // An error occurred
Alternatively, you can use kAudioDevicePropertyVolumeScalar to get the volume for a specific channel:

UInt32 channel = 1; // Channel 0  is master, if available
AudioObjectPropertyAddress propertyAddress =  
    kAudioDevicePropertyVolumeScalar, 
    kAudioDevicePropertyScopeOutput,
    channel 
;

if(!AudioObjectHasProperty(deviceID, &propertyAddress))
    // An error occurred

Float32 volume;
UInt32 dataSize = sizeof(volume);
OSStatus result = AudioObjectGetPropertyData(deviceID, &propertyAddress, 0, NULL, &dataSize, &volume);

if(kAudioHardwareNoError != result)
    // An error occurred

Apple 的文档中解释了两者之间的区别：

kAudioHardwareServiceDeviceProperty_VirtualMasterVolume

表示音量控制值的 Float32 值。此属性值的范围是 0.0（静音）到 1.0（全级别）。此属性的效果取决于与 HAL 音频对象关联的硬件设备。如果设备具有主音量控制，则此属性对其进行控制。如果设备具有单独的通道音量控件，则此属性适用于由设备的首选多通道布局标识的那些，或者如果设备只有立体声，则适用于首选立体声对。此控件在其影响的通道之间保持相对平衡。

因此，准确定义设备的音量可能很棘手，尤其是对于具有非标准通道映射的多通道设备。希望对你有帮助