Reading what you described it all depends on how you design your
application.
If you receive the audio streams independently and play them independently
(and simultaneously) then the Mixer API will not work for you. Because
though you can pass the waveout of which waveout created still the volume
change will affect all the streams being played.
I would probably choose this one
- if you are having separate input streams from eachone then convert each
stream to a PCM format.
- Process the PCM stream to determine the maximum/minimum levels and adjust
them accordingly.
Now that each stream is OK play them separately and simultaneously or use
some algorithm to mix them and play them.
Generally however if an input stream is too low or high then you'd better
adjust the microphone level (wavein) of the producer. Then you can filter or
do whatever processing needed.
To set the microphone volume use this
function SetMicrophoneVolume(ADeviceID: Integer; bValue: Word; AOpenFlag:
Cardinal): Boolean;
var
hMix: HMIXER;
mxlc: MIXERLINECONTROLS;
mxcd: TMIXERCONTROLDETAILS;
vol: TMIXERCONTROLDETAILS_UNSIGNED;
mxc: MIXERCONTROL;
mxl: TMixerLine;
intRet: Integer;
nMixerDevs: Integer;
cConnections: DWord;
j: DWORD;
begin
// Check if Mixer is available
Result := True;
nMixerDevs := mixerGetNumDevs();
if (nMixerDevs < 1) then
begin
Result := False;
exit;
end;
// open the mixer
intRet := mixerOpen(@hMix, ADeviceID, 0, 0, AOpenFlag);
if intRet = MMSYSERR_NOERROR then
begin
mxl.dwComponentType := MIXERLINE_COMPONENTTYPE_DST_WAVEIN;
mxl.cbStruct := SizeOf(mxl);
// get line info
intRet := mixerGetLineInfo(hMix, @mxl,
MIXER_GETLINEINFOF_COMPONENTTYPE);
if intRet = MMSYSERR_NOERROR then
begin
cConnections := mxl.cConnections;
for j := 0 to cConnections - 1 do
begin
mxl.dwSource := j;
mixerGetLineInfo(hMix, @mxl, MIXER_GETLINEINFOF_SOURCE);
if (MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE = mxl.dwComponentType)
then break;
end;
ZeroMemory(@mxlc, SizeOf(mxlc));
mxlc.cbStruct := SizeOf(mxlc);
mxlc.dwLineID := mxl.dwLineID;
mxlc.dwControlType := MIXERCONTROL_CONTROLTYPE_VOLUME;
mxlc.cControls := 1;
mxlc.cbmxctrl := SizeOf(mxc);
mxlc.pamxctrl := @mxc;
intRet := mixerGetLineControls(hMix, @mxlc,
MIXER_GETLINECONTROLSF_ONEBYTYPE);
if intRet = MMSYSERR_NOERROR then
begin
ZeroMemory(@mxcd, SizeOf(mxcd));
mxcd.dwControlID := mxc.dwControlID;
mxcd.cbStruct := SizeOf(mxcd);
mxcd.cMultipleItems := 0;
mxcd.cbDetails := SizeOf(Vol);
mxcd.paDetails := @vol;
mxcd.cChannels := 1;
vol.dwValue := bValue;
intRet := mixerSetControlDetails(hMix, @mxcd,
MIXER_SETCONTROLDETAILSF_VALUE);
if intRet <> MMSYSERR_NOERROR then
Result := False;
end
else
Result := False;
end
else Result := False;
mixerClose(hMix);
end;
end;
Where if you have the wavein handle call the function thisway:
SetMicrophoneVolume(waveinhadle, micvolume; MIXER_OBJECTF_HWAVEIN)
If you don't have the wavein handle you could call the function this way
SetMicrophoneVolume(SoundDeviceHandle, micvolume; MIXER_OBJECTF_WAVEIN)
The function returns True if there is a Microphone level control else
returns False
Hope this helps
"Dave Stallard" <stall
...@nospam.net> wrote in message
...
> My first post here; I think this is the right group to ask this question;
> if not, or if there are other relevant groups, please feel free to direct
> me to them.
> Background: I have a C++ WinXP speech recognition application that takes
> spoken input from a mike. It must interact with different people at
> different times, and these people's voices may have very different levels
> of amplitude. One person's speech might cause clipping, for example,
> while another's may be perfectly normal, or even too soft. It is thus not
> possible to select a fixed recording volume that is suitable for all.
> My query: How can my application change the machine's recording volume at
> will? For example, I'd like the app to be able to turn the volume down if
> it detects clipping. I know there is a setWaveOutVolume API, but I have
> also learned from various searches that there is no corresponding
> setWaveInVolume API. There *must* be a solution somehow. I'd prefer to
> have it be a simple one, if possible. ;)
> Just to make matters worse, we also use an Andrea USB SoundPod adapter, as
> well as direct connection the standard mike jack. Is there a solution
> that would work for both? (probably this is a dumb question)
> thanks,
> Dave
