objective-c - 如何获得 Mac 音频电平？

Question

目前，我的代码可以成功返回用户可以使用音量键设置的系统音频值。

但是，我想要的是扬声器播放的音频值。因此，如果用户正在观看 Netflix 并且某个角色开始尖叫，则返回的值会高于该角色在窃窃私语时的值。

我现在的代码:

+ (AudioDeviceID)defaultOutputDeviceID {
    OSStatus status = noErr;

    AudioDeviceID outputDeviceID = kAudioObjectUnknown;

    AudioObjectPropertyAddress propertyAOPA;
    propertyAOPA.mElement = kAudioObjectPropertyElementMaster;
    propertyAOPA.mScope = kAudioObjectPropertyScopeGlobal;
    propertyAOPA.mSelector = kAudioHardwarePropertyDefaultSystemOutputDevice;

    UInt32 propertySize = sizeof(outputDeviceID);

    if (!AudioHardwareServiceHasProperty(kAudioObjectSystemObject, &propertyAOPA)) {
        NSLog(@"Cannot find default output device!");
        return outputDeviceID;
    }

    status = AudioHardwareServiceGetPropertyData(kAudioObjectSystemObject, &propertyAOPA, 0, NULL, &propertySize, &outputDeviceID);

    if(status) {
        NSLog(@"Cannot find default output device!");
    }

    return outputDeviceID;
}

+ (float)volume {
    OSStatus status = noErr;

    AudioDeviceID outputDeviceID = [[self class] defaultOutputDeviceID];

    if (outputDeviceID == kAudioObjectUnknown) {
        NSLog(@"Unknown device");
        return 0.0;
    }

    AudioObjectPropertyAddress propertyAOPA;
    propertyAOPA.mElement = kAudioObjectPropertyElementMaster;
    propertyAOPA.mScope = kAudioDevicePropertyScopeOutput;
    propertyAOPA.mSelector = kAudioHardwareServiceDeviceProperty_VirtualMasterVolume;

    Float32 outputVolume;
    UInt32 propertySize = sizeof(outputVolume);

    if (!AudioHardwareServiceHasProperty(outputDeviceID, &propertyAOPA)) {
        NSLog(@"No volume returned for device 0x%0x", outputDeviceID);
        return 0.0;
    }

    status = AudioHardwareServiceGetPropertyData(outputDeviceID, &propertyAOPA, 0, NULL, &propertySize, &outputVolume);

    if (status) {
        NSLog(@"No volume returned for device 0x%0x", outputDeviceID);
        return 0.0;
    }

    if (outputVolume < 0.0 || outputVolume > 1.0)
        return 0.0;

    return outputVolume;
}

Answer 1

获取音量级别并根据需要进行设置(作为最大音量)，然后再次将其恢复为用户的原始音量级别。有关详细信息，您可以查看以下链接； https://stackoverflow.com/a/27743599/1351327
希望它会有所帮助。 (小心苹果会拒绝你的应用)