要用VB做多媒体程序的同志必看...

Csdn上已经有好多朋友问过诸如：
 “如何播放Avi、Wave、midi文件”、：
 “谁知道用api播放avi,mpg的详细方法？要可以设定将图像放置到设定的窗体中”、
 “如何同时播放两个Wav文件”
的问题，
其实用一个类模块就一切搞定，不需要什么控件之类的东西
下面这个类模块(不知从哪里找来的,好象就是CSDN)，我研究后将它修改得更好用了
将下面这个类模块存为Mmedia.cls
'----------------------------------------------------
Option Explicit

'--------------TrueZq 最新更新2001-01-12---------------------
'文件名：      MMedia.cls
'说明：   :  一个多媒体类,能播放Avi、Wave、Midi文件
'用法：
'Dim Multimedia As New Mmedia
'Multimedia.mmOpen "c:\test.wav"
'Multimedia.mmPlay
'！记住：在程序结束时，一定要用Set Multimedia=nothing释放资源！！！
'-----------------------------------------------------

' -=-=-=- 属性 -=-=-=-
' sFilename      当前的文件名
' nLength        文件长度（只读）
' nPosition      当前位置
' sStatus        当前状态（只读）
' bWait          True/False.决定是否等待播放完

' -=-=-=- 方法 -=-=-=-=-
' mmOpen <Filename>   打开要播放的文件
' mmClose             关闭当前文件
' mmPause             暂停
' mmStop              停止 停止后可以跳到开始再次播放
' mmSeek <Position>   Seeks to a position in the file
' mmPlay              播放

'--------------------------------------------------------------

Private sAlias As String        '别名
'Private hWnd As Long
Private sFilename As String     ' 当前的文件名
Private nLength As Single       ' 文件长度
                         
Private nPosition As Single     ' 当前位置
Private sStatus As String       ' 当前状态
Private bWait As Boolean        ' 决定是否等待播放完
Const WS_CHILD = &H40000000
'------------ API 声明 -------------
Private Declare Function mciSendString Lib "winmm.dll" _
   Alias "mciSendStringA" (ByVal lpstrCommand As String, _
   ByVal lpstrReturnString As String, ByVal uReturnLength As Long, _
   ByVal hwndCallback As Long) As Long

'Private Declare Function GetActiveWindow Lib "USER32" () As Integer

'当sTheFile是一个Avi文件时，参数hWnd指定动画在哪里播放
'若hWnd=0，则新开一个窗口播放动画。
'如果听不到Midi音乐，请在Windows下用媒体播放器测试一下。
'文件名不能带空格
Public Sub mmOpen(ByVal sTheFile As String, Optional hWnd As Long = 0)

    Dim nReturn As Long
    Dim sType As String '文件类型
    Static nNum As Integer
   
    If sAlias <> "" Then '关闭开始打开的文件
        mmClose
    End If
   
    If (Dir(sTheFile) = "") Then '判断是否是一个存在的文件
        sFilename = "文件" & sTheFile & " 不存在！"
        Exit Sub
    Else
        sFilename = sTheFile
'        nNum = nNum + 1
    End If
'    Stop
   sAlias = sFilename '用文件名作别名，避免别名冲突！
    ' 判断文件类型
    Select Case UCase$(Right$(sTheFile, 3))
       Case "WAV"
          sType = "Waveaudio"
       Case "AVI"
          sType = "AviVideo"
       
       Case "MID"
          sType = "Sequencer"
       Case Else
          ' 未知文件格式，退出。
          Exit Sub
    End Select
   
    If sType = "AviVideo" And hWnd > 0 Then
         nReturn = mciSendString("open " & sTheFile & " ALIAS " & sAlias _
            & " TYPE AVIVideo parent " & hWnd & " style " & LTrim$(Str$(WS_CHILD)), 0&, 0, 0)
    Else
        nReturn = mciSendString("Open " & sTheFile & " ALIAS " & sAlias _
            & " TYPE " & sType, "", 0, 0)
    End If
   
End Sub

'关闭当前打开的多媒体文件
Public Sub mmClose()
    Dim nReturn As Long
   
    '如果没有文件打开，则退出
    If sAlias = "" Then Exit Sub
   
    nReturn = mciSendString("Close " & sAlias, "", 0, 0)
    sAlias = ""
    sFilename = ""
   
End Sub

'暂停
Public Sub mmPause()
 
    Dim nReturn As Long
   
    If sAlias = "" Then
        Exit Sub
    ElseIf Status = "paused" Then '如果先前已经暂停了，则解除暂停
        mmPlay
    Else
        nReturn = mciSendString("Pause " & sAlias, "", 0, 0)
    End If
    'nPosition = Position
End Sub

'播放
Public Sub mmPlay()
  
    Dim nReturn As Long
   
    If sAlias = "" Then
        Exit Sub
    ElseIf Position = Length Then '如果已经到末尾
        mmSeek 0                  '跳到开始处
    End If
   
   
    If bWait Then
        nReturn = mciSendString("Play " & sAlias & " wait", "", 0, 0)
    Else
        nReturn = mciSendString("Play " & sAlias, "", 0, 0)
    End If
End Sub

'停止
'停止后跳到开始,以便再次播放
Public Sub mmStop()
 
    Dim nReturn As Long
  
    If sAlias = "" Then Exit Sub
   
    nReturn = mciSendString("Stop " & sAlias, "", 0, 0)
    mmSeek 0 '跳到开始位置
End Sub

'跳到指定的位置,并且处于暂停状态
'当nPosition的值>Length 或者nPosition<0时，将忽略这次操作
Public Sub mmSeek(ByVal nPosition As Single)
   
    Dim nReturn As Long
    nReturn = mciSendString("Seek " & sAlias & " to " & nPosition, "", 0, 0)

End Sub

'方法Filename返回当前打开的文件名
Property Get filename() As String
    filename = sFilename
End Property

'指定要播放的文件名，然后将它打开
'对于需要指定容器的Avi文件，不要以这种方式打开。
Property Let filename(ByVal sTheFile As String)

   mmOpen sTheFile
End Property

'读取属性Wait的值
'Msgbox Multimedia.Wait
Property Get Wait() As Boolean
   Wait = bWait
End Property

'设置等待属性
'用法：Multimedia.Wait=True
Property Let Wait(bWaitValue As Boolean)

   bWait = bWaitValue
End Property

'获得长度值
Property Get Length() As Single
  
   Dim nReturn As Long, nLength As Integer

   Dim sLength As String * 255
   
   If sAlias = "" Then
      Length = 0
      Exit Property
   End If

  nReturn = mciSendString("Status " & sAlias & " length", sLength, 255, 0)
  nLength = InStr(sLength, Chr$(0))
  Length = Val(Left$(sLength, nLength - 1))
End Property

Property Let Position(ByVal nPosition As Single)
    mmSeek nPosition
End Property

'获取当前位置
Property Get Position() As Single
 
   Dim nReturn As Integer, nLength As Integer
 
   Dim sPosition As String * 255

   If sAlias = "" Then Exit Property
   
 
   nReturn = mciSendString("Status " & sAlias & " position", sPosition, 255, 0)
   nLength = InStr(sPosition, Chr$(0))
   Position = Val(Left$(sPosition, nLength - 1))

End Property

'当前打开文件的状态
'有以下几种：playing paused stopped
Property Get Status() As String
 
   Dim nReturn As Integer, nLength As Integer
   Dim sStatus As String * 255
   

   If sAlias = "" Then Exit Property

   nReturn = mciSendString("Status " & sAlias & " mode", sStatus, 255, 0)
   
   nLength = InStr(sStatus, Chr$(0))
   Status = Left$(sStatus, nLength - 1)
   
End Property

'从头开始播放
Public Sub mmRestart()
    Dim nReturn As Long
   
    If sAlias = "" Then Exit Sub
  
    mmSeek 0
    mmPlay
End Sub

'类的初始化
Private Sub Class_Initialize()
'    sAlias = "" '别名初值为空
End Sub

'关闭打开的多媒体设备
'当该类的对象所在的窗体（或模块）卸载时，自动调用该过程
Private Sub Class_Terminate()
    mmClose
End Sub
'----------------------------------------------------
[用法]
1、
比如要在窗体上播放一个动画,只需3个语句就搞定。
Dim MmAvi As New Mmedia
MmAvi.mmOpen "G:\resource\Avi\Test.avi", Me.hWnd
MmAvi.mmPlay

2、循环播放
Private Sub Timer1_Timer()
    Dim S As String
    S = "当前文件：" & MmAvi.filename & vbCrLf & "当前位置：" & MmAvi.Position _
         & "总长度：" & MmAvi.Length & "当前状态：" & MmAvi.Status
    Label1.Caption = S
    If MmAvi.Status = "stopped" Then MmAvi.mmRestart
End sub

3、同时播放几个文件（类型可以相同、可以不同）
在Form1中加入Private MmWave(1) As New Mmedia
在需要播放的地方加上：
    MmWave(0).mmOpen "G:\resource\wave\m16.wav"
    MmWave(1).mmOpen "G:\resource\wave\Welcom98.wav"
    MmWave(0).mmPlay
    MmWave(1).mmPlay
4、将动画放入一个圆形区域播放

    Dim hr As Long
    Dim usew&, useh&
    Dim MmAvi As New Mmedia

    usew& = Frame1.Width / Screen.TwipsPerPixelX
    useh& = Frame1.Height / Screen.TwipsPerPixelY
    usew = useh
    hr& = CreateEllipticRgn(0, 0, usew, useh)
    Call SetWindowRgn(Frame1.hWnd, hr, True)
    MmAvi.mmOpen "G:\resource\Avi\start.avi", Frame1.hWnd
    MmAvi.mmPlay
………………………………