Control the Wave Volume

Author: Thomas Stutz

uses

MMSystem;

function GetWaveVolume(var LVol: DWORD; var RVol: DWORD): Boolean;

var

WaveOutCaps: TWAVEOUTCAPS;

Volume: DWORD;

begin

Result := False;

if WaveOutGetDevCaps(WAVE_MAPPER, @WaveOutCaps, SizeOf(WaveOutCaps)) = MMSYSERR_NOERROR then

if WaveOutCaps.dwSupport and WAVECAPS_VOLUME = WAVECAPS_VOLUME then

begin

Result := WaveOutGetVolume(WAVE_MAPPER, @Volume) = MMSYSERR_NOERROR;

LVol := LoWord(Volume);

RVol := HiWord(Volume);

end;

end;

{

The waveOutGetDevCaps function retrieves the capabilities of

a given waveform-audio output device.

The waveOutGetVolume function retrieves the current volume level

of the specified waveform-audio output device.

}

function SetWaveVolume(const AVolume: DWORD): Boolean;

var

WaveOutCaps: TWAVEOUTCAPS;

begin

Result := False;

if WaveOutGetDevCaps(WAVE_MAPPER, @WaveOutCaps, SizeOf(WaveOutCaps)) = MMSYSERR_NOERROR then

if WaveOutCaps.dwSupport and WAVECAPS_VOLUME = WAVECAPS_VOLUME then

Result := WaveOutSetVolume(WAVE_MAPPER, AVolume) = MMSYSERR_NOERROR;

end;

{

AVolume:

The low-order word contains the left-channel volume setting,

and the high-order word contains the right-channel setting.

A value of 65535 represents full volume, and a value of 0000 is silence.

If a device does not support both left and right volume control,

the low-order word of dwVolume specifies the volume level,

and the high-order word is ignored.

}

{ *** How to Use: ***}

// SetWaveVolume:

procedure TForm1.Button1Click(Sender: TObject);

var

LVol: Word;

RVol: Word;

begin

LVol := SpinEdit1.Value; // max. is 65535

RVol := SpinEdit2.Value; // max. is 65535

SetWaveVolume(MakeLong(LVol, RVol));

end;

// GetWaveVolume:

procedure TForm1.Button2Click(Sender: TObject);

var

LVol: DWORD;

RVol: DWORD;

begin

if GetWaveVolume(LVol, RVol) then

begin

SpinEdit1.Value := LVol;

SpinEdit2.Value := RVol;

end;

end;