delphi 设置系统静音以及恢复

  uses 

  MMSystem, ActiveX,ComObj;

type

  IAudioEndpointVolumeCallback = interface(IUnknown)

  ['{657804FA-D6AD-4496-8A60-352752AF4F89}']

  end;

  IAudioEndpointVolume = interface(IUnknown)

    ['{5CDF2C82-841E-4546-9722-0CF74078229A}']

    function RegisterControlChangeNotify(AudioEndPtVol: IAudioEndpointVolumeCallback): HRESULT; stdcall;

    function UnregisterControlChangeNotify(AudioEndPtVol: IAudioEndpointVolumeCallback): HRESULT; stdcall;

    function GetChannelCount(out PInteger): HRESULT; stdcall;

    function SetMasterVolumeLevel(fLevelDB: single; pguidEventContext: PGUID): HRESULT; stdcall;

    function SetMasterVolumeLevelScalar(fLevelDB: single; pguidEventContext: PGUID): HRESULT; stdcall;

    function GetMasterVolumeLevel(out fLevelDB: single): HRESULT; stdcall;

    function GetMasterVolumeLevelScaler(out fLevelDB: single): HRESULT; stdcall;

    function SetChannelVolumeLevel(nChannel: Integer; fLevelDB: double; pguidEventContext: PGUID): HRESULT; stdcall;

    function SetChannelVolumeLevelScalar(nChannel: Integer; fLevelDB: double; pguidEventContext: PGUID): HRESULT; stdcall;

    function GetChannelVolumeLevel(nChannel: Integer; out fLevelDB: double): HRESULT; stdcall;

    function GetChannelVolumeLevelScalar(nChannel: Integer; out fLevel: double): HRESULT; stdcall;

    function SetMute(bMute: Boolean; pguidEventContext: PGUID): HRESULT; stdcall;

    function GetMute(out bMute: Boolean): HRESULT; stdcall;

    function GetVolumeStepInfo(pnStep: Integer; out pnStepCount: Integer): HRESULT; stdcall;

    function VolumeStepUp(pguidEventContext: PGUID): HRESULT; stdcall;

    function VolumeStepDown(pguidEventContext: PGUID): HRESULT; stdcall;

    function QueryHardwareSupport(out pdwHardwareSupportMask): HRESULT; stdcall;

    function GetVolumeRange(out pflVolumeMindB: double; out pflVolumeMaxdB: double; out pflVolumeIncrementdB: double): HRESULT; stdcall;

  end;

  IAudioMeterInformation = interface(IUnknown)

  ['{C02216F6-8C67-4B5B-9D00-D008E73E0064}']

  end;

  IPropertyStore = interface(IUnknown)

  end;

  IMMDevice = interface(IUnknown)

  ['{D666063F-1587-4E43-81F1-B948E807363F}']

    function Activate(const refId: TGUID; dwClsCtx: DWORD;  pActivationParams: PInteger; out pEndpointVolume: IAudioEndpointVolume): HRESULT; stdCall;

    function OpenPropertyStore(stgmAccess: DWORD; out ppProperties: IPropertyStore): HRESULT; stdcall;

    function GetId(out ppstrId: PLPWSTR): HRESULT; stdcall;

    function GetState(out State: Integer): HRESULT; stdcall;

  end;

  IMMDeviceCollection = interface(IUnknown)

  ['{0BD7A1BE-7A1A-44DB-8397-CC5392387B5E}']

  end;

  IMMNotificationClient = interface(IUnknown)

  ['{7991EEC9-7E89-4D85-8390-6C703CEC60C0}']

  end;

  IMMDeviceEnumerator = interface(IUnknown)

  ['{A95664D2-9614-4F35-A746-DE8DB63617E6}']

    function EnumAudioEndpoints(dataFlow: TOleEnum; deviceState: SYSUINT; DevCollection: IMMDeviceCollection): HRESULT; stdcall;

    function GetDefaultAudioEndpoint(EDF: SYSUINT; ER: SYSUINT; out Dev :IMMDevice ): HRESULT; stdcall;

    function GetDevice(pwstrId: pointer; out Dev: IMMDevice): HRESULT; stdcall;

    function RegisterEndpointNotificationCallback(pClient: IMMNotificationClient): HRESULT; stdcall;

  end;

const

  CLASS_IMMDeviceEnumerator : TGUID = '{BCDE0395-E52F-467C-8E3D-C4579291692E}';

  IID_IMMDeviceEnumerator : TGUID = '{A95664D2-9614-4F35-A746-DE8DB63617E6}';

  IID_IAudioEndpointVolume : TGUID = '{5CDF2C82-841E-4546-9722-0CF74078229A}';

procedure SetMasterVolume(fLevelDB: single);

var

  pEndpointVolume: IAudioEndpointVolume;

  LDeviceEnumerator: IMMDeviceEnumerator;

  Dev: IMMDevice;

begin

  if not Succeeded(CoCreateInstance(CLASS_IMMDeviceEnumerator, nil, CLSCTX_INPROC_SERVER, IID_IMMDeviceEnumerator, LDeviceEnumerator)) then

   RaiseLastOSError;

  if not Succeeded(LDeviceEnumerator.GetDefaultAudioEndpoint($00000000, $00000000, Dev)) then

   RaiseLastOSError;

  if not Succeeded( Dev.Activate(IID_IAudioEndpointVolume, CLSCTX_INPROC_SERVER, nil, pEndpointVolume)) then

   RaiseLastOSError;

  if not Succeeded(pEndpointVolume.SetMasterVolumeLevelScalar(fLevelDB, nil)) then

   RaiseLastOSError;

end;

procedure TForm1.Button2Click(Sender: TObject);
begin
SetMasterVolume(0.0);
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
SetMasterVolume(5/10);
end;