delphi - How to check if the system master volume is mute or unmute?

Question

I'm using this code to mute/unmute system master volume:

const
  APPCOMMAND_VOLUME_MUTE = $80000;
  WM_APPCOMMAND = $319;

procedure TForm1.Button1Click(Sender: TObject);
begin
  // toggle mute/unmute
  SendMessageW(Handle, WM_APPCOMMAND, Handle, APPCOMMAND_VOLUME_MUTE);
end;

(Got the code from https://stackoverflow.com/a/154128/1140885)

It works fine on XP (Didn't test it on Win7 yet).
I need a method to check (get) what is the current "mute" state? Is it mute or not.
Any ideas?

---

Update: For XP I ended up using the code from here: How to get the master volume in windows xp? (Thanks to @Sertac Akyuz)

I had to change only a single line:

mxlc.dwControlType := MIXERCONTROL_CONTROLTYPE_VOLUME;

to:

mxlc.dwControlType := MIXERCONTROL_CONTROLTYPE_MUTE;

return value is either 0 (not mute) or 1 (mute).

Answer 1

Starting with Windows Vista you must use the Core Audio SDK to control the Windows audio. To check if the master volume is muted you must use the IAudioEndpointVolume.GetMute method.

Try this sample code

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Windows,
  ActiveX,
  ComObj;

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}';

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;

function IsMasterVolumeMute : Boolean;
var
  pEndpointVolume: IAudioEndpointVolume;
  LDeviceEnumerator: IMMDeviceEnumerator;
  Dev: IMMDevice;
  bMute: Boolean;
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.GetMute(bMute)) then
   RaiseLastOSError
  else
  Result:=bMute;
end;


begin
 try
    CoInitialize(nil);
    try
      Writeln(Format('Master Volume is Mute ? : %s',[BoolToStr(IsMasterVolumeMute, True)]));
    finally
      CoUninitialize;
    end;
 except
    on E:Exception do
        Writeln(E.Classname, ':', E.Message);
 end;
 Writeln('Press Enter to exit');
 Readln;
end.