Volume.exe: Set volume control levels using Visual Basic

Summary

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.

More Information

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 MIXER_GETLINEINFOF_COMPONENTTYPE = &H3&
    Public Const MIXER_GETCONTROLDETAILSF_VALUE = &H0&
    Public Const MIXER_GETLINECONTROLSF_ONEBYTYPE = &H2&
    Public Const MIXERLINE_COMPONENTTYPE_DST_FIRST = &H0&
    Public Const MIXERLINE_COMPONENTTYPE_SRC_FIRST = &H1000&

    Public Const MIXERLINE_COMPONENTTYPE_DST_SPEAKERS = _
    (MIXERLINE_COMPONENTTYPE_DST_FIRST + 4)

    Public Const MIXERLINE_COMPONENTTYPE_SRC_MICROPHONE = _
    (MIXERLINE_COMPONENTTYPE_SRC_FIRST + 3)

    Public Const MIXERLINE_COMPONENTTYPE_SRC_LINE = _
    (MIXERLINE_COMPONENTTYPE_SRC_FIRST + 2)

    Public Const MIXERCONTROL_CT_CLASS_FADER = &H50000000
    Public Const MIXERCONTROL_CT_UNITS_UNSIGNED = &H30000

    Public Const MIXERCONTROL_CONTROLTYPE_FADER = _
    (MIXERCONTROL_CT_CLASS_FADER Or _
    MIXERCONTROL_CT_UNITS_UNSIGNED)

    Public Const MIXERCONTROL_CONTROLTYPE_VOLUME = _
    (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

    Type MIXERCONTROLDETAILS
    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

    Type MIXERCONTROLDETAILS_UNSIGNED
    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

    Type MIXERLINECONTROLS
    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, _
    MIXER_GETLINEINFOF_COMPONENTTYPE)

    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, _
    MIXER_GETLINECONTROLSF_ONEBYTYPE)

    If (MMSYSERR_NOERROR = rc) Then
    GetVolumeControl = True

    ' Copy the control into the destination structure
    CopyStructFromPtr mxc, mxlc.pamxctrl, Len(mxc)
    Else
    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
    Dim vol As MIXERCONTROLDETAILS_UNSIGNED

    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, _
    MIXER_SETCONTROLDETAILSF_VALUE)

    GlobalFree (hmem)
    If (MMSYSERR_NOERROR = rc) Then
    SetVolumeControl = True
    Else
    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, _
    volCtrl)
    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, _
    micCtrl)
    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
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