如何使用混音器api控制Windows 7中的主混音器音量？

Question

In windows XP, it is quite easy to control master volume of a mixer device by setting volume of destination line using mixer api.It can be easily tested by sdk sample application provided by Microsoft.But in case of windows 7 whenever I open a mixer device in my application it shows it as new volume application and I am able to control only volume of my application.Not able to control complete sound of system.Can anyone suggest me how to control complete sound of speaker which will affect sound of all running application.

How can I change speakers volume using my application in windows 7 ?

Answer 1

I believe that the method you're looking for is SetMasterVolumeLevelScalar .

A short example in C (sorry for the lpVtbl s):

BOOL AddMasterVolumeLevelScalar(float fMasterVolumeAdd)
{
    IMMDeviceEnumerator *deviceEnumerator = NULL;
    IMMDevice *defaultDevice = NULL;
    IAudioEndpointVolume *endpointVolume = NULL;
    HRESULT hr;
    float fMasterVolume;
    BOOL bSuccess = FALSE;

    hr = CoCreateInstance(&XIID_MMDeviceEnumerator, NULL, CLSCTX_INPROC_SERVER, &XIID_IMMDeviceEnumerator, (LPVOID *)&deviceEnumerator);
    if(SUCCEEDED(hr))
    {
        hr = deviceEnumerator->lpVtbl->GetDefaultAudioEndpoint(deviceEnumerator, eRender, eConsole, &defaultDevice);
        if(SUCCEEDED(hr))
        {
            hr = defaultDevice->lpVtbl->Activate(defaultDevice, &XIID_IAudioEndpointVolume, CLSCTX_INPROC_SERVER, NULL, (LPVOID *)&endpointVolume);
            if(SUCCEEDED(hr))
            {
                if(SUCCEEDED(endpointVolume->lpVtbl->GetMasterVolumeLevelScalar(endpointVolume, &fMasterVolume)))
                {
                    fMasterVolume += fMasterVolumeAdd;

                    if(fMasterVolume < 0.0)
                        fMasterVolume = 0.0;
                    else if(fMasterVolume > 1.0)
                        fMasterVolume = 1.0;

                    if(SUCCEEDED(endpointVolume->lpVtbl->SetMasterVolumeLevelScalar(endpointVolume, fMasterVolume, NULL)))
                        bSuccess = TRUE;
                }

                endpointVolume->lpVtbl->Release(endpointVolume);
            }

            defaultDevice->lpVtbl->Release(defaultDevice);
        }

        deviceEnumerator->lpVtbl->Release(deviceEnumerator);
    }

    return bSuccess;
}

In case the GUIDs are not defined:

const static GUID XIID_IMMDeviceEnumerator = { 0xA95664D2, 0x9614, 0x4F35, { 0xA7, 0x46, 0xDE, 0x8D, 0xB6, 0x36, 0x17, 0xE6 } };
const static GUID XIID_MMDeviceEnumerator = { 0xBCDE0395, 0xE52F, 0x467C, { 0x8E, 0x3D, 0xC4, 0x57, 0x92, 0x91, 0x69, 0x2E } };
const static GUID XIID_IAudioEndpointVolume = { 0x5CDF2C82, 0x841E, 0x4546, { 0x97, 0x22, 0x0C, 0xF7, 0x40, 0x78, 0x22, 0x9A } };