VB.Net 使用没有 UI 的 avicap32.dll 捕获视频

Question

我正在尝试创建一个使用 avicap32.dll 录制视频的应用程序，但不使用用户界面。我找到的示例代码（显示如何录制视频而不仅仅是捕获图像的唯一代码）使用需要图片框的句柄 ID 的 hWnd。有什么办法可以绕过这个，只需连接到驱动程序，录制并保存视频？

我的代码如下：

    Imports System
    Imports System.Runtime.InteropServices
    Public Class Recorder
        Const WM_CAP_START = &H400S
        Const WS_CHILD = &H40000000
        Const WS_VISIBLE = &H10000000

        Const WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10
        Const WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11
        Const WM_CAP_EDIT_COPY = WM_CAP_START + 30
        Const WM_CAP_SEQUENCE = WM_CAP_START + 62
        Const WM_CAP_FILE_SAVEAS = WM_CAP_START + 23

        Const WM_CAP_SET_SCALE = WM_CAP_START + 53
        Const WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52
        Const WM_CAP_SET_PREVIEW = WM_CAP_START + 50

        Const SWP_NOMOVE = &H2S
        Const SWP_NOSIZE = 1
        Const SWP_NOZORDER = &H4S
        Const HWND_BOTTOM = 1

        Declare Function capGetDriverDescriptionA Lib "avicap32.dll" (ByVal wDriverIndex As Short, ByVal lpszName As String, ByVal cbName As Integer, ByVal lpszVer As String, ByVal cbVer As Integer) As Boolean

        Declare Function capCreateCaptureWindowA Lib "avicap32.dll" (ByVal lpszWindowName As String, ByVal dwStyle As Integer, ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Short, ByVal hWnd As Integer, ByVal nID As Integer) As Integer

        Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, ByVal Msg As Integer, ByVal wParam As Integer, <MarshalAs(UnmanagedType.AsAny)> ByVal lParam As Object) As Integer

        Private Shared Function ReturnDriver() As Integer 'As String
            Dim DriverName As String = Space(100)
            Dim DriverVersion As String = Space(100)
            'Dim ReturnDriverName As String = ""
            Dim DriverIndex As Integer = Nothing
            For i As Integer = 0 To 9
                If capGetDriverDescriptionA(i, DriverName, 80, DriverVersion, 80) Then
                    'lstVideoSources.Items.Add(DriverName.Trim)
                    'ReturnDriverName = DriverName.Trim
                    DriverIndex = i
                    Exit For
                End If
            Next
            Return DriverIndex
        End Function

        Public Shared Sub StartRecording()
            Dim DriverVersion As Integer = ReturnDriver()
            If SendMessage(0, WM_CAP_DRIVER_CONNECT, DriverVersion, 0) Then
                SendMessage(0, WM_CAP_SEQUENCE, 0, 0)
            End If
        End Sub

        Public Shared Sub StopRecording()
            SendMessage(0, WM_CAP_FILE_SAVEAS, 0, "C:\records\" & Now().ToString() & ".avi")
        End Sub
    End Class

Answer 1

我找到了答案。我一般习惯于web开发，不太习惯windows窗体开发，我意识到我可以创建一个图片框类型的变量，瞧，我有一个句柄可以参考。

关于信息，我在下面有我的代码，在我重新考虑它之后。

Const WM_CAP_START = &H400S
Const WS_CHILD = &H40000000
Const WS_VISIBLE = &H10000000

Const WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10
Const WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11
Const WM_CAP_EDIT_COPY = WM_CAP_START + 30
Const WM_CAP_SEQUENCE = WM_CAP_START + 62
Const WM_CAP_FILE_SAVEAS = WM_CAP_START + 23

Const WM_CAP_SET_SCALE = WM_CAP_START + 53
Const WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52
Const WM_CAP_SET_PREVIEW = WM_CAP_START + 50

Const SWP_NOMOVE = &H2S
Const SWP_NOSIZE = 1
Const SWP_NOZORDER = &H4S
Const HWND_BOTTOM = 1

Declare Function capGetDriverDescriptionA Lib "avicap32.dll" (ByVal wDriverIndex As Short, ByVal lpszName As String, ByVal cbName As Integer, ByVal lpszVer As String, ByVal cbVer As Integer) As Boolean

Declare Function capCreateCaptureWindowA Lib "avicap32.dll" (ByVal lpszWindowName As String, ByVal dwStyle As Integer, ByVal x As Integer, ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Short, ByVal hWnd As Integer, ByVal nID As Integer) As Integer

Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, ByVal Msg As Integer, ByVal wParam As Integer, <MarshalAs(UnmanagedType.AsAny)> ByVal lParam As Object) As Integer

Declare Function SetWindowPos Lib "user32" Alias "SetWindowPos" (ByVal hwnd As Integer, ByVal hWndInsertAfter As Integer, ByVal x As Integer, ByVal y As Integer, ByVal cx As Integer, ByVal cy As Integer, ByVal wFlags As Integer) As Integer

Declare Function DestroyWindow Lib "user32" (ByVal hndw As Integer) As Boolean

Private hWnd As Integer
Private DriverVersion As Integer
Private mypicture As PictureBox = New PictureBox()

Public Sub New()
    DriverVersion = ReturnDriver()
    hWnd = capCreateCaptureWindowA(DriverVersion, WS_VISIBLE Or WS_CHILD, 0, 0, 0, 0, mypicture.Handle.ToInt32, 0)
End Sub

Private Function ReturnDriver() As Integer
    Dim DriverName As String = Space(100)
    Dim DriverVersion As String = Space(100)
    Dim DriverIndex As Integer = Nothing
    For i As Integer = 0 To 9
        If capGetDriverDescriptionA(i, DriverName, 80, DriverVersion, 80) Then
            DriverIndex = i
            Exit For
        End If
    Next
    Return DriverIndex
End Function

Public Sub StartRecording()
    If SendMessage(hWnd, WM_CAP_DRIVER_CONNECT, DriverVersion, 0) Then
        SendMessage(hWnd, WM_CAP_SEQUENCE, 0, 0)
    End If
End Sub

Public Sub StopRecording(byval FileName As String)
    Try
        FileName = "C:/records/_" & FileName & ".avi"
        SendMessage(hWnd, WM_CAP_FILE_SAVEAS, 0, FileName)
        SendMessage(hWnd, WM_CAP_DRIVER_DISCONNECT, DriverVersion, 0)
        System.IO.File.Delete("C:/CAPTURE.avi")
    Catch ex As Exception

    End Try
End Sub

我没有运行代码，我看到无法使用 avicap32.dll 压缩视频，并且它正在为 10 秒的捕获保存 200 MB 视频。看来我必须理解 DirectShow.net。

Answer 2

你想要的很可能无法完成。 VFW 甚至一些 DS 过滤器/播放器都需要 hWnd 来绘制视频输出。没有它，就没有视频输出，因此没有什么可捕捉的。您可以尝试通过绘制到隐藏或屏幕外控件来欺骗它，但是 Windows 只是跳过绘画，因为它在屏幕外。 VFW 不是很灵活。