我没有 C 背景，所以指针似乎是我的失败。使用运行完整 Windows（Atom 处理器）的 Lenovo Thinkpad 平板电脑。我将示例项目 DXSnap 移植到 vb.net。它在我的笔记本电脑上运行良好，但在平板电脑上我遇到了错误。
第一个错误是：发生异常：System.Runtime.InteropServices.COMException (0x80070032)。不支持该请求。
第二个错误（关闭第一个错误后）：BufferCB 中的未初始化缓冲区。
我认为主要问题是我不确定要使用哪些视频设置。我从默认的 640x480x24bpp 开始。我通过将其更改为我从 videoInfoHeader 获得的内容（448x252）来解决我的第一个问题，尽管它没有返回我看到的 bpp。
来自 1 次运行的一些示例数据： Media Format Type: 05589f80-c356-11ce-bf01-00aa0055595a '这是常数，可能没问题 高度：252 宽度：448 m_stride: 1344 '很确定这是由程序计算的，应该没问题 pBuffer ：128778240 m_ipBuffer：81070712 缓冲区长度：338688 '常数。应该可以
我关心的子/功能：
Private Sub SetupGraph(dev As DsDevice, iWidth As Integer, iHeight As Integer, iBPP As Short, hControl As Control)
Dim hr As Integer
Dim sampGrabber As ISampleGrabber = Nothing
Dim capFilter As IBaseFilter = Nothing
Dim pCaptureOut As IPin = Nothing
Dim pSampleIn As IPin = Nothing
Dim pRenderIn As IPin = Nothing
' Get the graphbuilder object
m_FilterGraph = TryCast(New FilterGraph(), IFilterGraph2)
Try
#If DEBUG Then
m_rot = New DsROTEntry(m_FilterGraph)
#End If
' add the video input device
hr = m_FilterGraph.AddSourceFilterForMoniker(dev.Mon, Nothing, dev.Name, capFilter)
DsError.ThrowExceptionForHR(hr)
MsgBox(dev.Name.ToString & vbNewLine & dev.Mon.ToString & vbNewLine & capFilter.ToString)
' Find the still pin
m_pinStill = DsFindPin.ByCategory(capFilter, PinCategory.Still, 0)
' Didn't find one. Is there a preview pin?
If m_pinStill Is Nothing Then
m_pinStill = DsFindPin.ByCategory(capFilter, PinCategory.Preview, 0)
End If
' Still haven't found one. Need to put a splitter in so we have
' one stream to capture the bitmap from, and one to display. Ok, we
' don't *have* to do it that way, but we are going to anyway.
If m_pinStill Is Nothing Then
Dim pRaw As IPin = Nothing
Dim pSmart As IPin = Nothing
' There is no still pin
m_VidControl = Nothing
' Add a splitter
Dim iSmartTee As IBaseFilter = DirectCast(New SmartTee(), IBaseFilter)
Try
hr = m_FilterGraph.AddFilter(iSmartTee, "SmartTee")
DsError.ThrowExceptionForHR(hr)
' Find the find the capture pin from the video device and the
' input pin for the splitter, and connnect them
pRaw = DsFindPin.ByCategory(capFilter, PinCategory.Capture, 0)
pSmart = DsFindPin.ByDirection(iSmartTee, PinDirection.Input, 0)
hr = m_FilterGraph.Connect(pRaw, pSmart)
DsError.ThrowExceptionForHR(hr)
' Now set the capture and still pins (from the splitter)
m_pinStill = DsFindPin.ByName(iSmartTee, "Preview")
pCaptureOut = DsFindPin.ByName(iSmartTee, "Capture")
' If any of the default config items are set, perform the config
' on the actual video device (rather than the splitter)
If iHeight + iWidth + iBPP > 0 Then
SetConfigParms(pRaw, iWidth, iHeight, iBPP)
End If
Finally
If pRaw IsNot Nothing Then
Marshal.ReleaseComObject(pRaw)
End If
If Not pRaw Is pSmart Then
Marshal.ReleaseComObject(pSmart)
End If
If Not pRaw Is iSmartTee Then
Marshal.ReleaseComObject(iSmartTee)
End If
End Try
Else
' Get a control pointer (used in Click())
m_VidControl = TryCast(capFilter, IAMVideoControl)
pCaptureOut = DsFindPin.ByCategory(capFilter, PinCategory.Capture, 0)
' If any of the default config items are set
If iHeight + iWidth + iBPP > 0 Then
MsgBox("mPinStill: " & m_pinStill.ToString & vbNewLine & "iHeight: " & iHeight.ToString & vbNewLine & "iWidth: " & iWidth.ToString & vbNewLine & "bpp: " & iBPP.ToString)
SetConfigParms(m_pinStill, iWidth, iHeight, iBPP)
End If
End If
' Get the SampleGrabber interface
sampGrabber = TryCast(New SampleGrabber(), ISampleGrabber)
' Configure the sample grabber
Dim baseGrabFlt As IBaseFilter = TryCast(sampGrabber, IBaseFilter)
ConfigureSampleGrabber(sampGrabber)
pSampleIn = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Input, 0)
' Get the default video renderer
Dim pRenderer As IBaseFilter = TryCast(New VideoRendererDefault(), IBaseFilter)
hr = m_FilterGraph.AddFilter(pRenderer, "Renderer")
DsError.ThrowExceptionForHR(hr)
pRenderIn = DsFindPin.ByDirection(pRenderer, PinDirection.Input, 0)
' Add the sample grabber to the graph
hr = m_FilterGraph.AddFilter(baseGrabFlt, "Ds.NET Grabber")
DsError.ThrowExceptionForHR(hr)
If m_VidControl Is Nothing Then
' Connect the Still pin to the sample grabber
hr = m_FilterGraph.Connect(m_pinStill, pSampleIn)
DsError.ThrowExceptionForHR(hr)
' Connect the capture pin to the renderer
hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn)
DsError.ThrowExceptionForHR(hr)
Else
' Connect the capture pin to the renderer
hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn)
DsError.ThrowExceptionForHR(hr)
' Connect the Still pin to the sample grabber
hr = m_FilterGraph.Connect(m_pinStill, pSampleIn)
DsError.ThrowExceptionForHR(hr)
End If
' Learn the video properties
SaveSizeInfo(sampGrabber)
ConfigVideoWindow(hControl)
' Start the graph
Dim mediaCtrl As IMediaControl = TryCast(m_FilterGraph, IMediaControl)
hr = mediaCtrl.Run()
DsError.ThrowExceptionForHR(hr)
Finally
If sampGrabber IsNot Nothing Then
Marshal.ReleaseComObject(sampGrabber)
sampGrabber = Nothing
End If
If pCaptureOut IsNot Nothing Then
Marshal.ReleaseComObject(pCaptureOut)
pCaptureOut = Nothing
End If
If pRenderIn IsNot Nothing Then
Marshal.ReleaseComObject(pRenderIn)
pRenderIn = Nothing
End If
If pSampleIn IsNot Nothing Then
Marshal.ReleaseComObject(pSampleIn)
pSampleIn = Nothing
End If
End Try
End Sub
Private Function BufferCB(SampleTime As Double, pBuffer As IntPtr, BufferLen As Integer) As Integer Implements ISampleGrabberCB.BufferCB
' Note that we depend on only being called once per call to Click. Otherwise
' a second call can overwrite the previous image.
Debug.Assert(BufferLen = Math.Abs(1344) * 252, "Incorrect buffer length")
'Debug.Assert(BufferLen = Math.Abs(m_stride) * m_videoHeight, "Incorrect buffer length")
If m_WantOne Then
m_WantOne = False
MsgBox("P Buffer: " & pBuffer.ToString & "- Buffer Length: " & BufferLen.ToString & vbNewLine & "m_ipBuffer: " & m_ipBuffer.ToString)
Debug.Assert(m_ipBuffer <> IntPtr.Zero, "Unitialized buffer")
' Save the buffer
CopyMemory(m_ipBuffer, pBuffer, BufferLen)
MsgBox("After CopyMemory", MsgBoxStyle.AbortRetryIgnore)
' Picture is ready.
m_PictureReady.[Set]()
End If
Return 0
End Function
BufferCB 中的 CopyMemory 似乎是导致问题的原因，这就是为什么我认为缓冲区或视频大小/bpp 存在问题的原因。