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Volume Control

Posted on 1998-12-05
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Last Modified: 2013-12-03
How do you code a dialog slider control to perform the same function as the Windows master volume control.
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Question by:wayan
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Expert Comment

by:trillo
ID: 1416763
Just a quetion.... Do you need help for the slider control, or for the volume settings, or both?
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Author Comment

by:wayan
ID: 1416764
both, I am not sure on what API's to call and what if any structs to set up.
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trillo earned 50 total points
ID: 1416765
Which lengage are you using? C++?...
Anyway, while waiting for your answer I can tell you about the Windows' volume level: (I'll asume you use C++ in next lines)

You can use the "WaveOutGetVolume" and "WaveOutSetVolume" functions:
MMRESULT waveOutGetVolume(
    HWAVEOUT hwo, // Handle of a open waveout device
    LPDWORD pdwVolume // Adress of variable to be filled with the volume setting
   );
MMRESULT waveOutSetVolume(
    HWAVEOUT hwo,
    DWORD dwVolume
   );

The low-order word (from the second parameter of the function) contains the left-channel volume setting, and the high-order word contains the right-channel setting. A value of 0xFFFF represents full volume, and a value of 0x0000 is silence.
If a device does not support both left and right volume control, the low-order word of dwVolume specifies the volume level, and the high-order word is ignored.

You can use the HIWORD and LOWORD macros to separate the left and right channel volume values in the "WaveOutGetVolume" fucntion and you can use the MAKELONG macro to build the parameter form the left-right volume values in the "WaveOutSetVolume" function.

Trillo
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Author Comment

by:wayan
ID: 1416766
trillo

I would like an answer in "C" , the following is out of my Resource file:

CONTROL         "Slider1",IDC_VOLUME_SLIDER,"msctls_trackbar32",
                    TBS_AUTOTICKS | TBS_VERT | TBS_BOTH | WS_TABSTOP,54,14,26,47

-------------------------------
This is my case statement in the dialog callback.

case IDC_VOLUME_SLIDER:
?
?
?
?
return TRUE;
-------------------------

If you could fill in the gaps, I would be very happy

wayan


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Expert Comment

by:trillo
ID: 1416767
Inside your message loop you must have something like this.

switch(message)
{
   case WM_INITDIALOG:
       // Set here the track bar's properties
       SendMessage(hwndTrackBar, TBM_SETRANGE, (WPARAM)TRUE, MAKELONG(lMinimum, lMaximum);
       // wParam = Boolean value indicaten if control must be redrawn
       // lParam = low and high order words indicating the minimum and maximum values.
       return TRUE;
   case WM_VSCROLL:  // For a vertical scrollbar (as in your code)
       int newValue=SendMessage (hwndTrackBar, TBM_GETPOS, 0, 0);
       return TRUE;
   case ... (others)
}

-----------
As you see, your code was a little wrong, you don't need the ResourceID from your control, you only need the handle. Of course my code is very simple, but it basically shows how to precess the messages.
When the user changes, scrolls, clicks, etc... on the track bar you will recieve a WM_VSCROLL message for vertical trakbars and WM_HSCROLL message for horizontal track bars.
The you use the TBM_GETPOS message to retrieve the new value.

Trillo
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Expert Comment

by:trillo
ID: 1416768
All the code I posted on this page is valid for C and C++
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Author Comment

by:wayan
ID: 1416769
trillo this is what I think you have suggested that I do.
I have 2 more points that I would like you to clarify.
(the HOW DO I comments below)

-----------------------------------------
int iVmin = 0x0000;  // Volume minimum
int iVmax = 0xFFFF;  // Volume maximum
int iVpos;           // Current logical slider position
DWORD dwVolume;
HWAVEOUT hwo;           // Wave device handle

case WM_INITDIALOG:
// set limits
SendDlgItemMessage(hdlg, IDC_VOLUME_SLIDER,
                   TBM_SETRANGE ,
                   TRUE, MAKELONG(iVmin, iVmax));

// HOW DO I USE

WaveOutGetVolume(hwo, dwVolume);

//TO SETUP

SendDlgItemMessage(hdlg, IDC_VOLUME_SLIDER, TBM_SETPOS ,  ?, ?);

return TRUE;


---------------------------------------------------------

case WM_VSCROLL:
iVpos = SendDlgItemMessage(hdlg, IDC_VOLUME_SLIDER,
                           TBM_GETPOS , 0, 0);
                  
// HOW DO I USE iVpos TO SETUP

WaveOutSetVolume(hwo, dwVolume);

return TRUE;
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Expert Comment

by:trillo
ID: 1416770
a) You have to send a &reference to the function, because it will fill your variable with the volume. The trackbar's limits are the same as the volume limits, so we can use the same variable for the trakbar and the volume setting, without any interpolation.

WaveOutGetVolume(MAVE_MAPPER, &dwVolume);
SendDlgItemMessage(hdlg, IDC_VOLUME_SLIDER, TBM_SETPOS , TRUE, dwVolume);

b) TBM_GETPOS returns the trakbar's position and, as above, we use the same variable to set the volume.

case WM_VSCROLL:
  iVpos = SendDlgItemMessage(hdlg, IDC_VOLUME_SLIDER, TBM_GETPOS , 0, 0);
  WaveOutSetVolume(WAVE_MAPPER, iVpos);
  return TRUE;

Note that these 2 waveout functions need, in the first oparameter, a Handle of an open waveform-audio output device, but it can also be a device identifier.

Trillo
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