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