Capturing a photo on x86 Atom Windows 8, DirectShow


I don't have a C background, so pointers seem to be my downfall. Working with a Lenovo Thinkpad tablet running full blown Windows (Atom processor). I ported the sample project DXSnap to It works fine on my laptop, but on the tablet I'm getting errors.

First error is: Exception Occurred: System.Runtime.InteropServices.COMException (0x80070032). The request is not supported.

2nd error (after closing 1st error): Uninitialized Buffer in BufferCB.

I think the main problem is I'm not sure what video settings to use. I started with the default 640x480x24bpp. I moved past my first issues by changing it to what I was getting from the videoInfoHeader, which is 448x252, although it didn't return a bpp that I saw.

Some sample data from 1 run: Media Format Type: 05589f80-c356-11ce-bf01-00aa0055595a 'this is constant, probably ok Height: 252 Width: 448 m_stride: 1344 'Pretty sure this is calculated by the program, should be ok pBuffer: 128778240 m_ipBuffer: 81070712 Buffer Length: 338688 'constant. Should be ok

Subs/Functions of concern for me:

        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)
#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)
            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)
                    hr = m_FilterGraph.AddFilter(iSmartTee, "SmartTee")

                    ' 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)

                    ' 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
                    If pRaw IsNot Nothing Then
                    End If
                    If Not pRaw Is pSmart Then
                    End If
                    If Not pRaw Is iSmartTee Then
                    End If
                End Try

                ' 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)
            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")

            pRenderIn = DsFindPin.ByDirection(pRenderer, PinDirection.Input, 0)

            ' Add the sample grabber to the graph
            hr = m_FilterGraph.AddFilter(baseGrabFlt, "Ds.NET Grabber")

            If m_VidControl Is Nothing Then
                ' Connect the Still pin to the sample grabber
                hr = m_FilterGraph.Connect(m_pinStill, pSampleIn)

                ' Connect the capture pin to the renderer
                hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn)
                ' Connect the capture pin to the renderer
                hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn)

                ' Connect the Still pin to the sample grabber
                hr = m_FilterGraph.Connect(m_pinStill, pSampleIn)
            End If

            ' Learn the video properties

            ' Start the graph
            Dim mediaCtrl As IMediaControl = TryCast(m_FilterGraph, IMediaControl)
            hr = mediaCtrl.Run()
            If sampGrabber IsNot Nothing Then
                sampGrabber = Nothing
            End If
            If pCaptureOut IsNot Nothing Then
                pCaptureOut = Nothing
            End If
            If pRenderIn IsNot Nothing Then
                pRenderIn = Nothing
            End If
            If pSampleIn IsNot Nothing Then
                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.
        End If

        Return 0
    End Function

CopyMemory in BufferCB seems to be what is causing the issue, which is why I think there's a problem with the buffers, or video size/bpp.
asked on Stack Overflow Jun 13, 2013 by Aaron

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