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(Sen         


        

Answer 1

Use this snipped, I've tested it and works for me.
This will check and set master volume. (Copied from http://www.swissdelphicenter.ch/torry/showcode.php?id=1630)
I hope this helps:

 uses
      MMSystem;

    function GetMasterMute(
      Mixer: hMixerObj;
      var Control: TMixerControl): MMResult;
      // Returns True on success
    var
      Line: TMixerLine;
      Controls: TMixerLineControls;
    begin
      ZeroMemory(@Line, SizeOf(Line));
      Line.cbStruct := SizeOf(Line);
      Line.dwComponentType := MIXERLINE_COMPONENTTYPE_DST_SPEAKERS;
      Result := mixerGetLineInfo(Mixer, @Line,
        MIXER_GETLINEINFOF_COMPONENTTYPE);
      if Result = MMSYSERR_NOERROR then
      begin
        ZeroMemory(@Controls, SizeOf(Controls));
        Controls.cbStruct := SizeOf(Controls);
        Controls.dwLineID := Line.dwLineID;
        Controls.cControls := 1;
        Controls.dwControlType := MIXERCONTROL_CONTROLTYPE_MUTE;
        Controls.cbmxctrl := SizeOf(Control);
        Controls.pamxctrl := @Control;
        Result := mixerGetLineControls(Mixer, @Controls,
          MIXER_GETLINECONTROLSF_ONEBYTYPE);
      end;
    end;

    procedure SetMasterMuteValue(
      Mixer: hMixerObj;
      Value: Boolean);
    var
      MasterMute: TMixerControl;
      Details: TMixerControlDetails;
      BoolDetails: TMixerControlDetailsBoolean;
      Code: MMResult;
    begin
      Code := GetMasterMute(0, MasterMute);
      if Code = MMSYSERR_NOERROR then
      begin
        with Details do
        begin
          cbStruct := SizeOf(Details);
          dwControlID := MasterMute.dwControlID;
          cChannels := 1;
          cMultipleItems := 0;
          cbDetails := SizeOf(BoolDetails);
          paDetails := @BoolDetails;
        end;
        LongBool(BoolDetails.fValue) := Value;
        Code := mixerSetControlDetails(0, @Details,
    MIXER_SETCONTROLDETAILSF_VALUE);
      end;
      if Code <> MMSYSERR_NOERROR then
        raise Exception.CreateFmt('SetMasterMuteValue failure, '+
          'multimedia system error #%d', [Code]);
    end;

    // Example:

    procedure TForm1.Button1Click(Sender: TObject);
    begin
      SetMasterMuteValue(0, CheckBox1.Checked); // Mixer device #0 mute on/off
    end;