How to turn off the master volume of a sound card

Problem/Question/Abstract:

How to turn off the master volume of a sound card

Answer:

unit WaveUnit;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls,
  Forms, Dialogs, MMSystem, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  NumDevs: Integer;
  waveCaps: TWaveOutCaps;
  Volume: DWORD;
  Left, Right: Word;
  Version: Word;
begin
  { We should have at least one device }
  NumDevs := waveOutGetNumDevs;
  Edit1.Text := Format('Number of devices is %d', [NumDevs]);
  { for the 1st device (hard-coded) }
  {Get Device Caps}
  waveOutGetDevCaps(0, @waveCaps, SizeOf(waveCaps));
  { Show device caps }
  Memo1.Lines.Add('Device Caps: ' + waveCaps.szPName);
  Version := waveCaps.vDriverVersion;
  Memo1.Lines.Add(Format('Driver Version: %d.%d', [Hi(Version), Lo(Version)]));
  case waveCaps.wChannels of
    1: Memo1.Lines.Add('Left');
    2: Memo1.Lines.Add('Right');
  end;
  { Standard formats }
  if waveCaps.dwFormats and WAVE_FORMAT_1M08 <> 0 then
    Memo1.Lines.Add('11.025 kHz, mono, 8-bit');
  if waveCaps.dwFormats and WAVE_FORMAT_1M16 <> 0 then
    Memo1.Lines.Add('11.025 kHz, mono, 16-bit');

  {
  WAVE_FORMAT_1S08        11.025 kHz, stereo, 8-bit
  WAVE_FORMAT_1S16        11.025 kHz, stereo, 16-bit
  WAVE_FORMAT_2M08        22.05 kHz, mono, 8-bit
  WAVE_FORMAT_2M16        22.05 kHz, mono, 16-bit
  WAVE_FORMAT_2S08        22.05 kHz, stereo, 8-bit
  WAVE_FORMAT_2S16        22.05 kHz, stereo, 16-bit
  WAVE_FORMAT_4M08        44.1 kHz, mono, 8-bit
  WAVE_FORMAT_4M16        44.1 kHz, mono, 16-bit
  WAVE_FORMAT_4S08        44.1 kHz, stereo, 8-bit
  WAVE_FORMAT_4S16        44.1 kHz, stereo, 16-bit
  }

    { If Volume Control Supported }
  if waveCaps.dwSupport and WAVECAPS_VOLUME <> 0 then
  begin
    waveOutGetVolume(0, @Volume);
    Left := LoWord(Volume);
    Right := HiWord(Volume);
    { Show values of WAVE Device on volume control panel }
    Edit2.Text := Format('Left : %d, Right : %d', [Left, Right]);
    waveOutSetVolume(0, $40008000);
  end;
end;

end.