Posted on 1997-04-10
Last Modified: 2008-03-03
I've got a problem when setting the volume of the wave output. waveOutSetVolume takes 2 arguments; the first is the  id of the sounddevice and the second is the volume. The problem is that the second argument should be a unsigned long, but VB can just handle signed longs.
Anyone got a solution of how to solve this problem?

The code i have today (that doesnt fully work) is:
(left & right are the volume in percent)

Function SetVolume(left As Integer, right As Integer)
    Dim i As Integer
    Dim BothVolumes As Long
    Dim tt As Currency
    Dim tt2 As Currency
    CurrentVolLeft = (left * 65535) / 100
    CurrentVolRight = ((right * 65535) / 100) And &HFFFF&
    tt2 = CurrentVolRight
    If tt2 > 32767 Then
        tt = tt2 * 32768#
        tt = -tt
        tt = tt + 32767 * 65535
        tt = tt2 * 65535#
    End If
    tt = tt And &HFFFF0000
    CurrentVolRight = tt
    i = waveOutSetVolume(0, CurrentVolRight Or CurrentVolLeft)
End Function

Question by:coq

Expert Comment

ID: 1425199
Hi !

Long and Unsigned Long are same 32 bit data types.
the difference is only in that how Visual Basic Or C++ Interpritates (Convert) it into a number.

So If you write in Visual Basic:

dim a as long
msgbox a

So In Visual Basic You`ll Get -1
But In C++ When you Print it Using Printf you'll get
Number: 2^32 -1 (  4294967295 )

Function that Inputs ( L as Long) and Returns (L*2 as Long)
( So Windows function ( Not VB function) would get it as   UnsignedLong)

(0 <= L < 2^31)

Function L2UL(L As long) As Long
 Dim TL As Long
  If L < &H40000000 Then
   L2UL = L * 2
   TL = L Xor &H40000000
   L2UL = TL * 2 - 2 ^ 31
  End If
 End Function

Now You Can make Your Sub:

' Inputs Volume as long ( 0 <= Valume < 2^31)
Sub MywaveOutSetVolume ( Volume as long )
 dim NewValue as long
 NewValue = L2UL(Volume)
 waveOutSetVolume(0, NewValue)
End Sub

so MywaveOutSetVolume (17) same to waveOutSetVolume(0,34)
and MywaveOutSetVolume(2^31-1)same to waveOutSetVolume(0,2^32-2)

   I think that waveOutSetVolume is not Linear Function
   ( Volume of waveOutSetVolume(2*k) is not twice than  waveOutSetVolume(k), I think that the function is proportional to Log)
 !!! I haven't read the Help its only depends of my
     Physics Knowledge !!!!
I Hope it's will help you !!!



Accepted Solution

syberdyne earned 70 total points
ID: 1425200
When I have worked with setting the wave volume, I used the following function to combine the left and right volumes into the DoubleWord that is required.

Function MakeDWord(wHi As Long, wLo As Long) As Long
    If wHi And &H8000& Then
        MakeDWord = (((wHi And &H7FFF&) * 65536) Or (wLo And &HFFFF&)) Or &H80000000
        MakeDWord = (wHi * &H10000) + (wLo And &HFFFF&)
    End If
End Function

With this your function could be coded as follows:

Function SetVolume(left As Integer, right As Integer)
  Dim i As Integer
  Dim BothVolumes As Long
  Dim CurrentVolLeft As Long
  Dim CurrentVolRight As Long
  Dim tt As Currency
  Dim tt2 As Currency
  CurrentVolLeft = (left * 65535) / 100
  CurrentVolRight = (right * 65535) / 100
  BothVolumes = MakeDWord(CurrentVolLeft, CurrentVolRight)
  i = waveOutSetVolume(0, BothVolumes)
End Function


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