如何控制系统音量

'thanks to Rick Ratayczak of Future Works Media (rickr@execpc.com)
'save file and rename them to [name].BAS

Attribute VB_Name = "MIXER"
'****************************************************************************
'* This constant holds the value of the Highest Custom volume setting. The *
'* lowest value will always be zero. *
'****************************************************************************
Public Const HIGHEST_VOLUME_SETTING = 12

'Put these into a module
' device ID for aux device mapper
Public Const AUX_MAPPER = -1&
Public Const MAXPNAMELEN = 32

Type AUXCAPS
wMid As Integer
wPid As Integer
vDriverVersion As Long
szPname As String * MAXPNAMELEN
wTechnology As Integer
dwSupport As Long
End Type

' flags for wTechnology field in AUXCAPS structure
Public Const AUXCAPS_CDAUDIO = 1 ' audio from internal CD-ROM drive
Public Const AUXCAPS_AUXIN = 2 ' audio from auxiliary input jacks

' flags for dwSupport field in AUXCAPS structure
Public Const AUXCAPS_VOLUME = &H1 ' supports volume control
Public Const AUXCAPS_LRVOLUME = &H2 ' separate left-right volume control

Declare Function auxGetNumDevs Lib "winmm.dll" () As Long
Declare Function auxGetDeVCaps Lib "winmm.dll" Alias "auxGetDevCapsA" (ByVal uDeviceID As Long, lpCaps As AUXCAPS, ByVal uSize As Long) As Long

Declare Function auxSetVolume Lib "winmm.dll" (ByVal uDeviceID As Long, ByVal dwVolume As Long) As Long
Declare Function auxGetVolume Lib "winmm.dll" (ByVal uDeviceID As Long, ByRef lpdwVolume As Long) As Long
Declare Function auxOutMessage Lib "winmm.dll" (ByVal uDeviceID As Long, ByVal msg As Long, ByVal dw1 As Long, ByVal dw2 As Long) As Long

'****************************************************************************
'* Possible Return values from auxGetVolume, auxSetVolume *
'****************************************************************************
Public Const MMSYSERR_NOERROR = 0
Public Const MMSYSERR_BASE = 0
Public Const MMSYSERR_BADDEVICEID = (MMSYSERR_BASE 2)

'****************************************************************************
'* Use the CopyMemory function from the Windows API *
'****************************************************************************
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)

'****************************************************************************
'* Use this structure to break the Long into two Integers *
'****************************************************************************
Public Type VolumeSetting
LeftVol As Integer
RightVol As Integer
End Type

Sub lCrossFader()
'Vol1 = 100 - Slider1.Value ' Left
'Vol2 = 100 - Slider5.Value ' Right
'E = CrossFader.Value
'F = 100 - E
'If Check4.Value = 1 Then ' Half Fader Check
' LVol = (F * Val(Vol1) / 100) * 2
' RVol = (E * Val(Vol2) / 100) * 2
' If LVol > (50 * Val(Vol1) / 100) * 2 Then
' LVol = (50 * Val(Vol1) / 100) * 2
' End If
' If RVol > (50 * Val(Vol2) / 100) * 2 Then
' RVol = (50 * Val(Vol2) / 100) * 2
' End If
'Else
' LVol = (F * Val(Vol1) / 100)
' RVol = (E * Val(Vol2) / 100)
'End If
'Label1.Caption = "Fader: " LTrim$(Str$(LVol)) " x " LTrim$(Str$(RVol))
'
End Sub


Public Function lSetVolume(ByRef lLeftVol As Long, ByRef lRightVol As Long, lDeviceID As Long) As Long
'****************************************************************************
'* This function sets the current Windows volume settings to the specified *
'* device using two Custom numbers from 0 to HIGHEST_VOLUME_SETTING for the *
'* right and left volume settings. *
'* *
'* The return value of this function is the Return value of the auxGetVolume*
'* Windows API call. *
'****************************************************************************

Dim bReturnValue As Boolean ' Return Value from Function
Dim Volume As VolumeSetting ' Type structure used to convert a long to/from
' two Integers.

Dim lAPIReturnVal As Long ' Return value from API Call
Dim lBothVolumes As Long ' The API passed value of the Combined Volumes

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