windows下修改系统音量

#include <windows.h>
#include <mmdeviceapi.h>
#include <endpointvolume.h>
#include <audioclient.h>

//参数:
//	-2 恢复静音
//	-1 静音
//	0~100:音量比例
bool SetVolumeLevel(int level)
{
HRESULT hr;
IMMDeviceEnumerator* pDeviceEnumerator=0;
IMMDevice* pDevice=0;
IAudioEndpointVolume* pAudioEndpointVolume=0;
IAudioClient* pAudioClient=0;

try{
hr = CoCreateInstance(__uuidof(MMDeviceEnumerator),NULL,CLSCTX_ALL,__uuidof(IMMDeviceEnumerator),(void**)&pDeviceEnumerator);
if(FAILED(hr)) throw "CoCreateInstance";
hr = pDeviceEnumerator->GetDefaultAudioEndpoint(eRender,eMultimedia,&pDevice);
if(FAILED(hr)) throw "GetDefaultAudioEndpoint";
hr = pDevice->Activate(__uuidof(IAudioEndpointVolume),CLSCTX_ALL,NULL,(void**)&pAudioEndpointVolume);
if(FAILED(hr)) throw "pDevice->Active";
hr = pDevice->Activate(__uuidof(IAudioClient),CLSCTX_ALL,NULL,(void**)&pAudioClient);
if(FAILED(hr)) throw "pDevice->Active";

if(level==-2){
hr = pAudioEndpointVolume->SetMute(FALSE,NULL);
if(FAILED(hr)) throw "SetMute";
}else if(level==-1){
hr = pAudioEndpointVolume->SetMute(TRUE,NULL);
if(FAILED(hr)) throw "SetMute";
}else{
if(level<0 || level>100){
hr = E_INVALIDARG;
throw "Invalid Arg";
}

float fVolume;
fVolume = level/100.0f;
hr = pAudioEndpointVolume->SetMasterVolumeLevelScalar(fVolume,&GUID_NULL);
if(FAILED(hr)) throw "SetMasterVolumeLevelScalar";

pAudioClient->Release();
pAudioEndpointVolume->Release();
pDevice->Release();
pDeviceEnumerator->Release();
return true;
}
}
catch(...){
if(pAudioClient) pAudioClient->Release();
if(pAudioEndpointVolume) pAudioEndpointVolume->Release();
if(pDevice) pDevice->Release();
if(pDeviceEnumerator) pDeviceEnumerator->Release();
throw;
}
return false;
}

int main()
{
CoInitialize(0);
try{
//3秒后静音
Sleep(3000);
SetVolumeLevel(-1);
//3秒后恢复静音
Sleep(3000);
SetVolumeLevel(-2);
//调节音量
Sleep(3000);
SetVolumeLevel(10);
Sleep(3000);
SetVolumeLevel(30);
Sleep(3000);
SetVolumeLevel(20);
}
catch(...){
//错误处理...
}
CoUninitialize();
return 0;
}