Set Volume of Sound Card

uses MMSystem

//

procedure SetVolume(const volL, volR: Word);
var
  hWO: HWAVEOUT;
  waveF: TWAVEFORMATEX;
  vol: DWORD;
begin
  // init TWAVEFORMATEX
  FillChar(waveF, SizeOf(waveF), 0);
  // open WaveMapper = std output of playsound
  waveOutOpen(@hWO, WAVE_MAPPER, @waveF, 0, 0, 0);
  vol := volL + volR shl 16;
  // set volume
  waveOutSetVolume(hWO, vol);
  waveOutClose(hWO);
end;

function GetVolumeControl(aMixer: HMixer; componentType, ctrlType: Longint;
  var mxc: TMixerControl): Boolean;
var
  mxl: TMixerLine;
  mxlc: TMixerLineControls;
  rc: Longint;
begin
  Result := False;
  FillChar(mxl, SizeOf(TMixerLine), 0);
  mxl.cbStruct := SizeOf(TMixerLine);
  mxl.dwComponentType := componentType;
  {Obtain a line corresponding to the component type}
  rc := mixerGetLineInfo(aMixer, @mxl, MIXER_GETLINEINFOF_COMPONENTTYPE);
  if rc = MMSYSERR_NOERROR then
  begin
    with mxlc do
    begin
      cbStruct := SizeOf(TMixerLineControls);
      dwLineID := mxl.dwLineID;
      dwControlType := ctrlType;
      cControls := 1;
      cbmxctrl := SizeOf(TMixerLine);
      pamxctrl := @mxc;
      pamxctrl^.cbStruct := SizeOf(TMixerControl);
    end;
    mixerGetLineControls(aMixer, @mxlc, MIXER_GETLINECONTROLSF_ONEBYTYPE);
    rc := mixerGetLineControls(aMixer, @mxlc, MIXER_GETLINECONTROLSF_ONEBYTYPE);
    Result := rc = MMSYSERR_NOERROR;
  end;
end;

function SetVolumeControl(aMixer: HMixer; mxc: TMixerControl; volume: Longint): Boolean;
var
  mxcd: TMixerControlDetails;
  vol: TMixerControlDetails_Unsigned;
  rc: MMRESULT;
begin
  FillChar(mxcd, SizeOf(mxcd), 0);
  with mxcd do
  begin
    cbStruct := SizeOf(TMixerControlDetails);
    dwControlID := mxc.dwControlID;
    cbDetails := SizeOf(TMixerControlDetails_Unsigned);
    paDetails := @vol;
    cMultipleItems := 0;
    cChannels := 1;
  end;
  vol.dwValue := volume;
  rc := mixerSetControlDetails(aMixer, @mxcd, MIXER_SETCONTROLDETAILSF_VALUE);
  Result := rc = MMSYSERR_NOERROR;
end;

function InitMixer: HMixer;
var
  Err: MMRESULT;
begin
  Err := mixerOpen(@Result, 0, 0, 0, 0);
  if Err <> MMSYSERR_NOERROR then
    Result := 0;
end;

procedure SetMasterVolumeToZero;
var
  MyMixerHandle: HMixer;
  MyVolCtrl: TMixerControl;
begin
  MyMixerHandle := InitMixer;
  if MyMixerHandle <> 0 then
    try
      FillChar(MyVolCtrl, SizeOf(MyVolCtrl), 0);
      if GetVolumeControl(MyMixerHandle, MIXERLINE_COMPONENTTYPE_DST_SPEAKERS,
        MIXERCONTROL_CONTROLTYPE_VOLUME, MyVolCtrl) then
      begin
        {The last parameter (0) here is the volume level}
        if SetVolumeControl(MyMixerHandle, MyVolCtrl, 0) then
          ShowMessage('Volume should now be set to zero');
      end;
    finally
      mixerClose(MyMixerHandle);
    end;
end;

// Beispiel 1
procedure TForm1.Button1Click(Sender: TObject);
begin
  SetVolume(14000, 14000);
end;

// Beispiel 2
procedure TForm1.Button2Click(Sender: TObject);
begin
  SetMasterVolumeToZero;
end;