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Re: Monitoring audio levels


2004-04-01 07:51:37 PM
cppbuilder49
Not all Soundcards have PEAKMETERS (SoundBlasters and AC97's do NOT have them, and hence, cannot display a
level meter on the standard Windows mixer control), so this rules out the methods discussed before. Is there a
way to periodically read 4 bytes from each channel on the soundcard's output? It seems an absurdly simple
thing to do, but the grief it has caused me so far is incredible!!! Surely, all I would need is the address of
the primary sound buffer in order to read from it. I have the DirectSound header file and library, but I can't
get the dang thing working for lack of documentation and examples. Has anyone got anything on DirectSound out
there that isn't MSDN and has proper examples that work, and don't use the DirectSound8 interface, but use the
one supplied with BCB5?
--
Mark Jacobs
DK Computing
www.dkcomputing.co.uk
XXXX@XXXXX.COM
"Pete Fraser" < XXXX@XXXXX.COM >wrote in message
Quote
You don't want the volume - that's the value of the 'volume control'
Look for MIXERCONTROL which defines xxx_CLASS_METER for different Audio
channels(Lines) and also mixerGetLineControls() which is used to get the
information.
(BTW I've never done this so I'm just searchng help)
Do look at www.torry.net as they have several controls for doing similar
things. I've seen audio metering components there - just can't remember
where :(

HTH Pete

"Mark Jacobs" < XXXX@XXXXX.COM >wrote in
message news: XXXX@XXXXX.COM ...
>I have looked, tried, tinkered and fretted. I do not know whether to open
waveIn or waveOut in order to
>monitor currently playing levels. I keep getting "An invalid flag was
passed to a system function." (code 10)
>from the following code :-

<snipped lots>


 
 

Re:Re: Monitoring audio levels

Here is how to do it :-
// In the public section of your form, add the following :-
public: // User declarations
char erst[199];
unsigned char wvbfr[99];
HWAVEIN phwo;
WAVEFORMATEX pwfx;
MMRESULT wh;
WAVEHDR wvhd;
void __fastcall ProcessInput();
// then on the form's paint event put this :-
//--------------------------------------------------------------------------
void __fastcall TForm1::FormPaint(TObject *Sender)
{
static bool clld=false;
if (clld) return;
clld=true;
pwfx.cbSize=0;
pwfx.wFormatTag=WAVE_FORMAT_PCM;
pwfx.nChannels=2;
pwfx.nSamplesPerSec=44100;
pwfx.wBitsPerSample=16;
pwfx.nAvgBytesPerSec=44100*2*16/8;
pwfx.nBlockAlign=2*16/8;
wh=waveInOpen(&phwo,WAVE_MAPPER,&pwfx,(DWORD)WaveInProc,
(DWORD)this,CALLBACK_FUNCTION);
if (wh!=MMSYSERR_NOERROR)
{
waveOutGetErrorText(wh,erst,190);
Edit3->Text="Error="+AnsiString(erst);
zcMMTimer1->Enabled=false;
}
else zcMMTimer1->Enabled=true;
}
//--------------------------------------------------------------------------
// Somewhere in the form module declare the following callback functions :-
void CALLBACK WaveInProc(HWAVEIN waveIn,UINT uMsg,
DWORD dwInstance,
DWORD dwParam1,DWORD dwParam2)
{
if (uMsg==MM_WIM_DATA) Form1->ProcessInput();
}
//--------------------------------------------------------------------------
void __fastcall TForm1::ProcessInput()
{
short *mybf=(short *)wvbfr;
waveInStop(phwo);
wh=waveInUnprepareHeader(phwo,&wvhd,sizeof(WAVEHDR));
if (wh!=MMSYSERR_NOERROR) return;
zcDinMeter1->Value=(int)mybf[0]*100*zSlideBar1->Value/32768;
zcDinMeter2->Value=(int)mybf[1]*100*zSlideBar1->Value/32768;
zcMMTimer1->Enabled=true;
}
//--------------------------------------------------------------------------
/*
Add a timer to the form. It should be set to an interval of 50ms or less to
be useful, but 100ms seems to be adequate. I use Ziegler's Multimedia Timer
so I can get good results from 20ms resolution. In the timer's OnTimer
event, put the following :-
*/
//--------------------------------------------------------------------------
void __fastcall TForm1::zcMMTimer1Timer(TObject *Sender)
{
unsigned int vl; int mcierr,ii,jj;
zcMMTimer1->Enabled=false;
wvbfr[0]='\0'; wvbfr[1]='\0'; wvbfr[2]='\0'; wvbfr[3]='\0';
wvhd.lpData=wvbfr; wvhd.dwBufferLength=4;
wvhd.dwLoops=0; wvhd.dwFlags=0; waveInStop(phwo);
if (waveInPrepareHeader(phwo,&wvhd,sizeof(WAVEHDR))==MMSYSERR_NOERROR)
{
waveInAddBuffer(phwo,&wvhd,sizeof(WAVEHDR));
waveInStart(phwo);
}
}
//--------------------------------------------------------------------------
// In the form closequery event, put this :-
//--------------------------------------------------------------------------
-
void __fastcall TForm1::FormCloseQuery(TObject *Sender, bool &CanClose)
{
zcMMTimer1->Enabled=false; waveInStop(phwo);
waveInUnprepareHeader(phwo,&wvhd,sizeof(WAVEHDR));
waveInClose(phwo); CanClose=true;
}
//--------------------------------------------------------------------------
-
Hey presto, the values in ProcessInput()'s mybf buffer are :-
Left Channel = mybf[0]
Right Channel=mybf[1]
with a range of -32767 to 32767 in each case.
I verified my results on a Soundblaster Live card. I have noticed that the
Realtek AC97 Soundcard on another PC did not work properly. It could be
indicative of faulty sound drivers. I'll try other PCs and report back.
However, the code above has been arrived at painstakingly. Thankyou
Microsoft!
--
Mark Jacobs
"iim" < XXXX@XXXXX.COM >wrote in message
Quote

I need a small program to measure the signal level from microphone via
sound card. Anybody can help ?
"Mark Jacobs" < XXXX@XXXXX.COM >wrote in
message news: XXXX@XXXXX.COM ...
Not all Soundcards have PEAKMETERS (SoundBlasters and AC97's do NOT have
them, and hence, cannot display a
level meter on the standard Windows mixer control), so this rules out the
methods discussed before. Is there a
way to periodically read 4 bytes from each channel on the soundcard's
output? It seems an absurdly simple
thing to do, but the grief it has caused me so far is incredible!!! ...
 

Re:Re: Monitoring audio levels

I have had problems with Ziegler's Multimedia Timer, so use a standard system
timer. I can get as low as 20ms interval
--
Mark Jacobs
 

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