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Private Const HIGHEST_VOLUME_SETTING = 100 '%
Private Const AUX_MAPPER = -1&
Private Const MAXPNAMELEN = 32
Private Const AUXCAPS_CDAUDIO = 1 ' audio from internal CD-ROM drive
Private Const AUXCAPS_AUXIN = 2 ' audio from auxiliary input jacks
Private Const AUXCAPS_VOLUME = &H1         ' supports volume control
Private Const AUXCAPS_LRVOLUME = &H2         ' separate left-right volume control
Private Const MMSYSERR_NOERROR = 0
Private Const MMSYSERR_BASE = 0
Private Type AUXCAPS
     wMid As Integer
     wPid As Integer
     vDriverVersion As Long
     szPname As String * MAXPNAMELEN
     wTechnology As Integer
     dwSupport As Long
End Type
Private Type VolumeSetting
    LeftVol As Integer
    RightVol As Integer
End Type
Private Declare Function auxGetNumDevs Lib "winmm.dll" () As Long
Private Declare Function auxGetDevCaps Lib "winmm.dll" Alias "auxGetDevCapsA" (ByVal uDeviceID As Long, lpCaps As AUXCAPS, ByVal uSize As Long) As Long
Private Declare Function auxSetVolume Lib "winmm.dll" (ByVal uDeviceID As Long, ByVal dwVolume As Long) As Long
Private Declare Function auxGetVolume Lib "winmm.dll" (ByVal uDeviceID As Long, ByRef lpdwVolume As VolumeSetting) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
Private Function nSigned(ByVal lUnsignedInt As Long) As Integer
    Dim nReturnVal As Integer                         ' Return value from Function
    If lUnsignedInt > 65535 Or lUnsignedInt < 0 Then
        MsgBox "Error in conversion from Unsigned to nSigned Integer"
        nSignedInt = 0
        Exit Function
    End If
    If lUnsignedInt > 32767 Then
        nReturnVal = lUnsignedInt - 65536
        nReturnVal = lUnsignedInt
    End If
    nSigned = nReturnVal
End Function
Private Function lUnsigned(ByVal nSignedInt As Integer) As Long
    Dim lReturnVal As Long                         ' Return value from Function
    If nSignedInt < 0 Then
        lReturnVal = nSignedInt + 65536
        lReturnVal = nSignedInt
    End If
    If lReturnVal > 65535 Or lReturnVal < 0 Then
        MsgBox "Error in conversion from nSigned to Unsigned Integer"
        lReturnVal = 0
    End If
    lUnsigned = lReturnVal
End Function
Private Function lSetVolume(ByRef lLeftVol As Long, ByRef lRightVol As Long, lDeviceID As Long) As Long
    Dim Volume As VolumeSetting, lBothVolumes As Long
    Volume.LeftVol = nSigned(lLeftVol * 65535 / HIGHEST_VOLUME_SETTING)
    Volume.RightVol = nSigned(lRightVol * 65535 / HIGHEST_VOLUME_SETTING)
    'copy our Volume-variable to a long
    CopyMemory lBothVolumes, Volume.LeftVol, Len(Volume)
    'call the SetVolume-function
    lSetVolume = auxSetVolume(lDeviceID, lBothVolumes)
End Function
Private Sub Form_Load()
    'KPD-Team 2000
    Dim Volume As VolumeSetting, Cnt As Long, AC As AUXCAPS
    'set the output to a persistent graphic
    Me.AutoRedraw = True
    'loop through all the devices
    For Cnt = 0 To auxGetNumDevs - 1 'auxGetNumDevs is zero-based
        'get the volume
        auxGetVolume Cnt, Volume
        'get the device capabilities
        auxGetDevCaps Cnt, AC, Len(AC)
        'print the name on the form
        Me.Print "Device #" + Str$(Cnt + 1) + ": " + Left(AC.szPname, InStr(AC.szPname, vbNullChar) - 1)
        'print the left- and right volume on the form
        Me.Print "Left volume:" + Str$(HIGHEST_VOLUME_SETTING * lUnsigned(Volume.LeftVol) / 65535)
        Me.Print "Right volume:" + Str$(HIGHEST_VOLUME_SETTING * lUnsigned(Volume.RightVol) / 65535)
        'set the left- and right-volume to 50%
        lSetVolume 50, 50, Cnt
        Me.Print "Both volumes now set to 50%"
        'empty line
End Sub

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