Please Help API/DLL
Fernando
I need count the frames of a AVI media file - the length.
I made the code bellow and it works well in VB.6 but not in VB.NET
Why does not work in DOT.NET ? I tried to change TYPE to STRUCTURE, and
ByVal to ByRef in API calls, but without sucess.
I then made a VB.6 DLL of this sample code and use it within VB.NET, but
this is slow, it needs to register in anothe computer...
Please tell me why I can't use it within VB.NET
thank you very much
Private Const OF_SHARE_DENY_WRITE As Long = &H20
Private Type AVIFileInfo
dwMaxBytesPerSec As Long
dwFlags As Long
dwCaps As Long
dwStreams As Long
dwSuggestedBufferSize As Long
dwWidth As Long
dwHeight As Long
dwScale As Long
dwRate As Long
dwLength As Long
dwEditCount As Long
szFileType As String * 64
End Type
Private Declare Function AVIFileOpen Lib "avifil32" Alias "AVIFileOpenA" _
(ppfile As Long, ByVal szFile As String, ByVal mode As Long, pclsidHandler _
As Any) As Long
Private Declare Function AVIFileRelease Lib "avifil32" (ByVal pfile As Long)
_
As Long
Private Declare Function AVIFileInfo Lib "avifil32" Alias "AVIFileInfoA" _
(ByVal pfile As Long, pfi As AVIFileInfo, ByVal lSize As Long) As Long
Private Declare Sub AVIFileInit Lib "avifil32" ()
Private Declare Sub AVIFileExit Lib "avifil32" ()
Public Function getFrames(ByVal aviFile As String) As String
Dim hFile As Long, AviInfo As AVIFileInfo
AVIFileInit
'create a handle to the AVI file
If AVIFileOpen(hFile, aviFile, OF_SHARE_DENY_WRITE, ByVal 0&) = 0 Then
'retrieve the AVI information
If AVIFileInfo(hFile, AviInfo, Len(AviInfo)) = 0 Then
getFrames = CStr(AviInfo.dwLength)
Else
getFrames = "#Error#"
End If
'release the file handle
AVIFileRelease hFile
Else
getFrames = "#Error#"
End If
'exit the AVIFile library and decrement the reference count for the
library
AVIFileExit
End Function
Mattias Sjögren
You also have to adjust the data types, such as changing Long to
Integer.
>and ByVal to ByRef in API calls
That you shouldn't do.
Mattias
--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.
Fernando
I did made that changes in order to run within VB.NET, but I allways get
this error :
changed Long to Integer
and ANY to integer
An unhandled exception of type 'System.NullReferenceException' occurred in
WindowsApplication1.exe
Additional information: Object reference not set to an instance of an
object.
can't do it :((
the new code is this :
Module Module1
Private Const OF_SHARE_DENY_WRITE As Integer = &H20
Private Structure AVIInfo
Dim dwMaxBytesPerSec As Integer
Dim dwFlags As Integer
Dim dwCaps As Integer
Dim dwStreams As Integer
Dim dwSuggestedBufferSize As Integer
Dim dwWidth As Integer
Dim dwHeight As Integer
Dim dwScale As Integer
Dim dwRate As Integer
Dim dwLength As Integer
Dim dwEditCount As Integer
Dim szFileType As String
End Structure
Private Declare Function AVIFileOpen Lib "avifil32" Alias "AVIFileOpenA"
_
(ByVal ppfile As Integer, ByVal szFile As String, ByVal mode As Integer,
ByVal pclsidHandler _
As Integer) As Integer
Private Declare Function AVIFileRelease Lib "avifil32" (ByVal pfile As
Integer) _
As Integer
Private Declare Function AVIFileInfo Lib "avifil32" Alias "AVIFileInfoA"
_
(ByVal pfile As Integer, ByVal pfi As AVIInfo, ByVal lSize As Integer)
As Integer
Private Declare Sub AVIFileInit Lib "avifil32" ()
Private Declare Sub AVIFileExit Lib "avifil32" ()
Public Function getFrames(ByVal aviFile As String) As String
Dim hFile As Integer, AviInfo As AVIInfo
AVIFileInit()
'create a handle to the AVI file
If AVIFileOpen(hFile, aviFile, OF_SHARE_DENY_WRITE, 0) = 0 Then
'retrieve the AVI information
If AVIFileInfo(hFile, AviInfo, Len(AviInfo)) = 0 Then
getFrames = CStr(AviInfo.dwLength)
Else
getFrames = "#Error#"
End If
'release the file handle
AVIFileRelease(hFile)
Else
getFrames = "#Error#"
End If
'exit the AVIFile library and decrement the reference count for the
library
AVIFileExit()
End Function
End Module
Mattias Sjögren
...
> Dim szFileType As String
Add the attribute <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=64)>
to this field.
> Private Declare Function AVIFileOpen Lib "avifil32" Alias "AVIFileOpenA"
>_
> (ByVal ppfile As Integer, ByVal szFile As String, ByVal mode As Integer,
>ByVal pclsidHandler _
> As Integer) As Integer
ppfile should be ByRef here or you wont get a valid file pointer back.
> Private Declare Function AVIFileInfo Lib "avifil32" Alias "AVIFileInfoA"
>_
> (ByVal pfile As Integer, ByVal pfi As AVIInfo, ByVal lSize As Integer)
>As Integer
pfi should be ByRef.
Fernando
it works now and I don't need a VB.6 DL anymore
the code is this :
========
Imports System.Runtime.InteropServices
Module Module1
Private Const OF_SHARE_DENY_WRITE As Integer = &H20
Private Structure AVIInfo
Dim dwMaxBytesPerSec As Integer
Dim dwFlags As Integer
Dim dwCaps As Integer
Dim dwStreams As Integer
Dim dwSuggestedBufferSize As Integer
Dim dwWidth As Integer
Dim dwHeight As Integer
Dim dwScale As Integer
Dim dwRate As Integer
Dim dwLength As Integer
Dim dwEditCount As Integer
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=64)> Dim szFileType
As String
End Structure
Private Declare Function AVIFileOpen Lib "avifil32" Alias "AVIFileOpenA"
(ByRef ppfile As Integer, ByVal szFile As String, ByVal mode As Integer,
ByVal pclsidHandler As Integer) As Integer
Private Declare Function AVIFileRelease Lib "avifil32" (ByVal pfile As
Integer) As Integer
Private Declare Function AVIFileInfo Lib "avifil32" Alias "AVIFileInfoA"
(ByVal pfile As Integer, ByRef pfi As AVIInfo, ByRef lSize As Integer) As
Integer
Private Declare Sub AVIFileInit Lib "avifil32" ()
Private Declare Sub AVIFileExit Lib "avifil32" ()
Public Function getFrames(ByVal aviFile As String) As String
Dim hFile As Integer, AviInfo As AVIInfo
Dim tmp As String
AVIFileInit()
'create a handle to the AVI file
If AVIFileOpen(hFile, aviFile, OF_SHARE_DENY_WRITE, tmp) = 0 Then
'retrieve the AVI information
If AVIFileInfo(hFile, AviInfo, Len(AviInfo)) = 0 Then
getFrames = CStr(AviInfo.dwLength)
Else
getFrames = "#Error#"
End If
'release the file handle
AVIFileRelease(hFile)
Else
getFrames = "#Error#"
End If
'exit the AVIFile library and decrement the reference count for the
AVIFileExit()
End Function
End Module