set the volume for the microphone/ mute it

function SetMicrophoneVolume(bValue: Word): Boolean;
var {0..65535}
hMix: HMIXER;
mxlc: MIXERLINECONTROLS;
mxcd: TMIXERCONTROLDETAILS;
vol: TMIXERCONTROLDETAILS_UNSIGNED;
mxc: MIXERCONTROL;
mxl: TMixerLine;
intRet: Integer;
nMixerDevs: Integer;
begin
// Check if Mixer is available
// Überprüfen, ob ein Mixer vorhanden
nMixerDevs := mixerGetNumDevs();
if (nMixerDevs <>then
begin
Exit;
end;

// open the mixer
intRet := mixerOpen(@hMix, 0, 0, 0, 0);
if intRet = MMSYSERR_NOERROR then
begin
mxl.dwComponentType := MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE;
mxl.cbStruct := SizeOf(mxl);

{*} // this option will tell the compiler which line destination to take:
{*} // 0 - PLAYBACK destination
{*} // 1 - RECORD destination
{*} // this time the compiler will take control of recording microphone line
{*} mxl.dwDestination := 1;


// get line info
intRet := mixerGetLineInfo(hMix, @mxl, MIXER_GETLINEINFOF_COMPONENTTYPE);

//...
end;
end;