Volume.exe: Set volume control levels using Visual Basic

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Volume.exe is a self-extracting compressed file that contains a sample project demonstrating how to set the volume and microphone levels using Visual Basic.

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After downloading and running the self-extracting file, the following files are copied to the Volume Level Project directory on your hard drive:
  Form1.frm    - the main form in the project
  Module1.bas  - the module containing the function and type declarations.
  Project1.vbp - the project file
  Project1.vbw - the project workspace file
  Readme.txt   - you are currently reading this file.
To set these microphone and volume levels from Visual Basic, use the following Windows API functions:
  • GlobalAlloc - allocates the specified number of bytes from the heap.
  • GlobalLock - locks a global memory object and returns a pointer to the first byte of the object's memory block. The memory block associated with a locked memory object cannot be moved or discarded.
  • GlobalFree - frees the specified global memory object and invalidates its handle.
  • mixerClose - closes the specified mixer device.
  • mixerGetControlDetails - retrieves details about a single control associated with an audio line.
  • mixerGetDevCaps - queries a specified mixer device to determine its capabilities.
  • mixerGetID - retrieves the device identifier for a mixer device associated with a specified device handle.
  • mixerGetLineControls - retrieves one or more controls associated with an audio line.
  • mixerGetLineInfo - retrieves information about a specific line of a mixer device.
  • mixerGetNumDevs - retrieves the number of mixer devices present in the system.
  • mixerMessage - sends a custom mixer driver message directly to a mixer driver.
  • mixerOpen - opens a specified mixer device and ensures that the device will not be removed until the application closes the handle.
  • mixerSetControlDetails - sets properties of a single control associated with an audio line.
The next section shows how to create a sample project that uses these functions to set the volume and microphone levels.

Create the Sample Project

  1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
  2. Add two command buttons, two text boxes, and two labels to Form1.
  3. Add a Module to the project by completing the following steps:
    1. From the Project menu, click Add module. The Add Module dialog box appears.
    2. From the New tab, choose Module and click OK. A new module is added to your project.
  4. Copy the following code to the Code window of Module1:
          Option Explicit
          Public Const MMSYSERR_NOERROR = 0
          Public Const MAXPNAMELEN = 32
          Public Const MIXER_LONG_NAME_CHARS = 64
          Public Const MIXER_SHORT_NAME_CHARS = 16
          Public Const MIXERLINE_COMPONENTTYPE_SRC_FIRST = &H1000&
                         (MIXERLINE_COMPONENTTYPE_DST_FIRST + 4)
                         (MIXERLINE_COMPONENTTYPE_SRC_FIRST + 3)
                         (MIXERLINE_COMPONENTTYPE_SRC_FIRST + 2)
          Public Const MIXERCONTROL_CT_CLASS_FADER = &H50000000
          Public Const MIXERCONTROL_CT_UNITS_UNSIGNED = &H30000
                         (MIXERCONTROL_CT_CLASS_FADER Or _
                         (MIXERCONTROL_CONTROLTYPE_FADER + 1)
          Declare Function mixerClose Lib "winmm.dll" _
                         (ByVal hmx As Long) As Long
          Declare Function mixerGetControlDetails Lib "winmm.dll" _
                         Alias "mixerGetControlDetailsA" _
                         (ByVal hmxobj As Long, _
                         pmxcd As MIXERCONTROLDETAILS, _
                         ByVal fdwDetails As Long) As Long
          Declare Function mixerGetDevCaps Lib "winmm.dll" _
                         Alias "mixerGetDevCapsA" _
                         (ByVal uMxId As Long, _
                         ByVal pmxcaps As MIXERCAPS, _
                         ByVal cbmxcaps As Long) As Long
          Declare Function mixerGetID Lib "winmm.dll" _
                         (ByVal hmxobj As Long, _
                         pumxID As Long, _
                         ByVal fdwId As Long) As Long
          Declare Function mixerGetLineControls Lib "winmm.dll" _
                         Alias "mixerGetLineControlsA" _
                         (ByVal hmxobj As Long, _
                         pmxlc As MIXERLINECONTROLS, _
                         ByVal fdwControls As Long) As Long
          Declare Function mixerGetLineInfo Lib "winmm.dll" _
                         Alias "mixerGetLineInfoA" _
                         (ByVal hmxobj As Long, _
                         pmxl As MIXERLINE, _
                         ByVal fdwInfo As Long) As Long
          Declare Function mixerGetNumDevs Lib "winmm.dll" () As Long
          Declare Function mixerMessage Lib "winmm.dll" _
                         (ByVal hmx As Long, _
                         ByVal uMsg As Long, _
                         ByVal dwParam1 As Long, _
                         ByVal dwParam2 As Long) As Long
          Declare Function mixerOpen Lib "winmm.dll" _
                         (phmx As Long, _
                         ByVal uMxId As Long, _
                         ByVal dwCallback As Long, _
                         ByVal dwInstance As Long, _
                         ByVal fdwOpen As Long) As Long
          Declare Function mixerSetControlDetails Lib "winmm.dll" _
                         (ByVal hmxobj As Long, _
                         pmxcd As MIXERCONTROLDETAILS, _
                         ByVal fdwDetails As Long) As Long
          Declare Sub CopyStructFromPtr Lib "kernel32" _
                         Alias "RtlMoveMemory" _
                         (struct As Any, _
                         ByVal ptr As Long, _
                         ByVal cb As Long)
          Declare Sub CopyPtrFromStruct Lib "kernel32" _
                         Alias "RtlMoveMemory" _
                         (ByVal ptr As Long, _
                         struct As Any, _
                         ByVal cb As Long)
          Declare Function GlobalAlloc Lib "kernel32" _
                         (ByVal wFlags As Long, _
                         ByVal dwBytes As Long) As Long
          Declare Function GlobalLock Lib "kernel32" _
                         (ByVal hmem As Long) As Long
          Declare Function GlobalFree Lib "kernel32" _
                         (ByVal hmem As Long) As Long
          Type MIXERCAPS
             wMid As Integer                   '  manufacturer id
             wPid As Integer                   '  product id
             vDriverVersion As Long            '  version of the driver
             szPname As String * MAXPNAMELEN   '  product name
             fdwSupport As Long                '  misc. support bits
             cDestinations As Long             '  count of destinations
          End Type
          Type MIXERCONTROL
             cbStruct As Long           '  size in Byte of MIXERCONTROL
             dwControlID As Long        '  unique control id for mixer device
             dwControlType As Long      '  MIXERCONTROL_CONTROLTYPE_xxx
             fdwControl As Long         '  MIXERCONTROL_CONTROLF_xxx
             cMultipleItems As Long     '  if MIXERCONTROL_CONTROLF_MULTIPLE
                                        '  set
             szShortName As String * MIXER_SHORT_NAME_CHARS  ' short name of
                                                             ' control
             szName As String * MIXER_LONG_NAME_CHARS        ' long name of
                                                             ' control
             lMinimum As Long           '  Minimum value
             lMaximum As Long           '  Maximum value
             reserved(10) As Long       '  reserved structure space
             End Type
             cbStruct As Long       '  size in Byte of MIXERCONTROLDETAILS
             dwControlID As Long    '  control id to get/set details on
             cChannels As Long      '  number of channels in paDetails array
             item As Long           '  hwndOwner or cMultipleItems
             cbDetails As Long      '  size of _one_ details_XX struct
             paDetails As Long      '  pointer to array of details_XX structs
          End Type
             dwValue As Long        '  value of the control
          End Type
          Type MIXERLINE
             cbStruct As Long               '  size of MIXERLINE structure
             dwDestination As Long          '  zero based destination index
             dwSource As Long               '  zero based source index (if
                                            '  source)
             dwLineID As Long               '  unique line id for mixer device
             fdwLine As Long                '  state/information about line
             dwUser As Long                 '  driver specific information
             dwComponentType As Long        '  component type line connects to
             cChannels As Long              '  number of channels line supports
             cConnections As Long           '  number of connections (possible)
             cControls As Long              '  number of controls at this line
             szShortName As String * MIXER_SHORT_NAME_CHARS
             szName As String * MIXER_LONG_NAME_CHARS
             dwType As Long
             dwDeviceID As Long
             wMid  As Integer
             wPid As Integer
             vDriverVersion As Long
             szPname As String * MAXPNAMELEN
          End Type
             cbStruct As Long       '  size in Byte of MIXERLINECONTROLS
             dwLineID As Long       '  line id (from MIXERLINE.dwLineID)
                                    '  MIXER_GETLINECONTROLSF_ONEBYID or
             dwControl As Long      '  MIXER_GETLINECONTROLSF_ONEBYTYPE
             cControls As Long      '  count of controls pmxctrl points to
             cbmxctrl As Long       '  size in Byte of _one_ MIXERCONTROL
             pamxctrl As Long       '  pointer to first MIXERCONTROL array
          End Type
          Function GetVolumeControl(ByVal hmixer As Long, _
                                  ByVal componentType As Long, _
                                  ByVal ctrlType As Long, _
                                  ByRef mxc As MIXERCONTROL) As Boolean
          ' This function attempts to obtain a mixer control.
          ' Returns True if successful.
             Dim mxlc As MIXERLINECONTROLS
             Dim mxl As MIXERLINE
             Dim hmem As Long
             Dim rc As Long
             mxl.cbStruct = Len(mxl)
             mxl.dwComponentType = componentType
             ' Obtain a line corresponding to the component type
             rc = mixerGetLineInfo(hmixer, _
                                   mxl, _
             If (MMSYSERR_NOERROR = rc) Then
                 mxlc.cbStruct = Len(mxlc)
                 mxlc.dwLineID = mxl.dwLineID
                 mxlc.dwControl = ctrlType
                 mxlc.cControls = 1
                 mxlc.cbmxctrl = Len(mxc)
                 ' Allocate a buffer for the control
                 hmem = GlobalAlloc(&H40, Len(mxc))
                 mxlc.pamxctrl = GlobalLock(hmem)
                 mxc.cbStruct = Len(mxc)
                 ' Get the control
                 rc = mixerGetLineControls(hmixer, _
                                           mxlc, _
                 If (MMSYSERR_NOERROR = rc) Then
                     GetVolumeControl = True
                     ' Copy the control into the destination structure
                     CopyStructFromPtr mxc, mxlc.pamxctrl, Len(mxc)
                     GetVolumeControl = False
                 End If
                 GlobalFree (hmem)
                 Exit Function
             End If
             GetVolumeControl = False
          End Function
          Function SetVolumeControl(ByVal hmixer As Long, _
                                  mxc As MIXERCONTROL, _
                                  ByVal volume As Long) As Boolean
          ' This function sets the value for a volume control.
          ' Returns True if successful
             Dim mxcd As MIXERCONTROLDETAILS
             mxcd.item = 0
             mxcd.dwControlID = mxc.dwControlID
             mxcd.cbStruct = Len(mxcd)
             mxcd.cbDetails = Len(vol)
             ' Allocate a buffer for the control value buffer
             hmem = GlobalAlloc(&H40, Len(vol))
             mxcd.paDetails = GlobalLock(hmem)
             mxcd.cChannels = 1
             vol.dwValue = volume
             ' Copy the data into the control value buffer
             CopyPtrFromStruct mxcd.paDetails, vol, Len(vol)
             ' Set the control value
             rc = mixerSetControlDetails(hmixer, _
                                        mxcd, _
             GlobalFree (hmem)
             If (MMSYSERR_NOERROR = rc) Then
                 SetVolumeControl = True
                 SetVolumeControl = False
             End If
          End Function
  5. Copy the following code to the Code window of Form1:
          Option Explicit
          Dim hmixer As Long          ' mixer handle
          Dim volCtrl As MIXERCONTROL ' waveout volume control
          Dim micCtrl As MIXERCONTROL ' microphone volume control
          Dim rc As Long              ' return code
          Dim ok As Boolean           ' boolean return code
          Dim vol As Long             ' volume  
          Private Sub Form_Load()
          ' Open the mixer with deviceID 0.
             rc = mixerOpen(hmixer, 0, 0, 0, 0)
             If ((MMSYSERR_NOERROR <> rc)) Then
                 MsgBox "Couldn't open the mixer."
                 Exit Sub
                 End If
             ' Get the waveout volume control
             ok = GetVolumeControl(hmixer, _
                                  MIXERLINE_COMPONENTTYPE_DST_SPEAKERS, _
                                  MIXERCONTROL_CONTROLTYPE_VOLUME, _
             If (ok = True) Then
                 ' If the function successfully gets the volume control,
                 ' the maximum and minimum values are specified by
                 ' lMaximum and lMinimum
                 Label1.Caption = volCtrl.lMinimum _
                                  & " to " _
                                  & volCtrl.lMaximum
                 End If
             ' Get the microphone volume control
             ok = GetVolumeControl(hmixer, _
                                  MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE, _
                                  MIXERCONTROL_CONTROLTYPE_VOLUME, _
             If (ok = True) Then
                 Label2.Caption = micCtrl.lMinimum _
                                  & " to " _
                                  & micCtrl.lMaximum
                 End If
          End Sub
          Private Sub Command1_Click()
             vol = CLng(Text1.Text)
             SetVolumeControl hmixer, volCtrl, vol
          End Sub
          Private Sub Command2_Click()
             vol = CLng(Text2.Text)
             SetVolumeControl hmixer, micCtrl, vol
          End Sub
  6. On the Run menu, click Start or press the F5 key to start the program. Minimize the Visual Basic IDE so all that appears on your display is Form1. Maximize the Volume Level program in the Task bar. Arrange Form1 and the Volume Level program so both programs are visible.
  7. Enter a value between the minimum and maximum values shown in one or both text boxes and click one of the command buttons in Form1. Note that the corresponding slider in the Volume Level program is adjusted to your specified level.
(c) Microsoft Corporation 1997, All Rights Reserved.
Contributions by Arsenio Locsin, Microsoft Corporation


Article ID: 178456 - Last Review: June 22, 2014 - Revision: 6.0
Applies to
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 6.0 Professional Edition
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