Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpszCommand As String, ByVal lpszReturnString As String, ByVal cchReturnLength As Long, ByVal hwndCallback As Long) As Long
mciSendString sends a command to a Multimedia Control Interface (MCI) device. The command strings used with this function can perform almost any task necessary for using a multimedia device installed on the computer. mciSendString provides a relatively easy way to perform multimedia output operations.
Look at the MCI command strings page for a list of some of the command strings used by the mciSendString function.
If successful, the function returns 0. If an error occured, the function returns a nonzero MCI error code. To get a textual description of the error, use the mciGetErrorString function.
None.
To run this code, place two command buttons on a form window. Name one "cmdPlay" and set its Caption to "&Play MIDI File". Likewise, name the other one "cmdStop" and set its Caption to "&Stop MIDI File".
' This code is licensed according to the terms and conditions listed here. ' Declarations and such needed for the example: ' (Copy them to the (declarations) section of a module.) Public Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal _ lpszCommand As String, ByVal lpszReturnString As String, ByVal cchReturnLength _ As Long, ByVal hwndCallback As Long) As Long Public Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal _ fdwError As Long, ByVal lpszErrorText As String, ByVal cchErrorText As Long) As Long ' Use the MCI to play or stop playback of a MIDI file. The file C:\Music\canyon.mid ' is opened when the form opens. The Play and Stop buttons behave as you'd expect. The ' only potential surprise is that the current position is not reset when playback stops; it ' behaves just as pausing playback would. The file closes when the form unloads. ' If anything goes wrong in the example, display a message box with ' the MCI error message text. Private Sub Form_Load() ' Open the file "C:\Music\canyon.mid" for later use in the example. ' Give it an alias of "canyon" so we don't need to refer to the filename again. Dim errcode As Long ' MCI error code errcode = mciSendString("open C:\Music\canyon.mid alias canyon", "", 0, 0) If errcode <> 0 Then DisplayError errcode End Sub Private Sub cmdPlay_Click() ' Begin playback of the MIDI file when this button is pressed. Dim errcode As Long ' MCI error code errcode = mciSendString("play canyon", "", 0, 0) If errcode <> 0 Then DisplayError errcode End Sub Private Sub cmdStop_Click() ' Stop playback of the MIDI file when this button is pressed. ' The position within the file does not move back to the beginning. Dim errcode As Long ' MCI error code errcode = mciSendString("stop canyon", "", 0, 0) If errcode <> 0 Then DisplayError errcode End Sub Private Sub Form_Unload(Cancel As Integer) ' Close the MIDI file when the form unloads. This is important, because the ' MIDI driver can only work with one file at a time. There's no need to check ' for an error here, since we're just closing the file. Dim errcode As Long ' MCI error code errcode = mciSendString("close canyon", "", 0, 0) End Sub Private Sub DisplayError(ByVal errcode As Long) ' This subroutine displays a dialog box with the text of the MCI error. There's ' no reason to use the MessageBox API function; VB's MsgBox function will suffice. Dim errstr As String ' MCI error message text Dim retval As Long ' return value ' Get a string explaining the MCI error. errstr = Space(128) retval = mciGetErrorString(errcode, errstr, Len(errstr)) ' Remove the terminating null and empty space at the end. errstr = Left(errstr, InStr(errstr, vbNullChar) - 1) ' Display a simple error message box. retval = MsgBox(errstr, vbOKOnly Or vbCritical) End Sub
mciGetErrorString
Media Control Interface (MCI)
Back to the Function list.
Back to the Reference section.
Last Modified: July 4, 2000
This page is copyright © 2000 Paul Kuliniewicz. Copyright Information Revised October 29, 2000
Go back to the Windows API Guide home page.
E-mail: vbapi@vbapi.com Send Encrypted E-Mail
This page is at http://www.vbapi.com/ref/m/mcisendstring.html