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    Pregunta:  30299 - CONTROLAR VOLUMEN EN DELPHI
Autor:  Enrique Ortiz Herrera
Hola Amigos de LWP

Quisiera saber si existe alguna forma de controlar el volumen de la tarjeta de sonido desde una aplicacion en Delphi 3, resulta que estoy desarrollando una aplicacion que me permite escuchar archivos Wav y/o MP3, pero no se como puedo controlar el volumen en la reproduccion.

Mucho les agradeceria si me pudieran ayudar

Saludos y de Antemano muchas Gracias.
  Respuesta:  Miguel Lucero
Espero que esto te sirva

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;

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

{************************************************}

{2.}

{by Serhiy Perevoznyk}

uses
MMSystem;

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;