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dwmapi get vBlank RRS feed

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    Hello,

    I'm looking to get the vBlank time in order to synchronize a camera to the vertical blank timing of the projector I have connected to my computer.  I understand I can get the vBlank timing from from the DwmGetCompositionTimingInfo function.

    I'm using basic net in VS2010 and have written the following code:

        <System.Runtime.InteropServices.DllImport("dwmapi.dll")> _
    Private Shared Function DwmGetCompositionTimingInfo(ByVal hwnd As IntPtr, ByRef DWM_TIMING_INFO As DWM_TIMING_INFO) As Integer
    End Function

    Private Structure DWM_TIMING_INFO
        Public cbSize As UInt32
        Public rateRefresh As UNSIGNED_RATIO
        Public qpcRefreshPeriod As QPC_TIME
        Public rateCompose As UNSIGNED_RATIO
        Public qpcVBlank As QPC_TIME
        Public cRefresh As DWM_FRAME_COUNT
        Public cDXRefresh As UInteger
        Public qpcCompose As QPC_TIME
        Public cFrame As DWM_FRAME_COUNT
        Public cDXPresent As UInteger
        Public cRefreshFrame As DWM_FRAME_COUNT
        Public cFrameSubmitted As DWM_FRAME_COUNT
        Public cDXPresentSubmitted As UInteger
        Public cFrameConfirmed As DWM_FRAME_COUNT
        Public cDXPresentConfirmed As UInteger
        Public cRefreshConfirmed As DWM_FRAME_COUNT
        Public cDXRefreshConfirmed As UInteger
        Public cFramesLate As DWM_FRAME_COUNT
        Public cFramesOutstanding As UInteger
        Public cFrameDisplayed As DWM_FRAME_COUNT
        Public qpcFrameDisplayed As QPC_TIME
        Public cRefreshFrameDisplayed As DWM_FRAME_COUNT
        Public cFrameComplete As DWM_FRAME_COUNT
        Public qpcFrameComplete As QPC_TIME
        Public cFramePending As DWM_FRAME_COUNT
        Public qpcFramePending As QPC_TIME
        Public cFramesDisplayed As DWM_FRAME_COUNT
        Public cFramesComplete As DWM_FRAME_COUNT
        Public cFramesPending As DWM_FRAME_COUNT
        Public cFramesAvailable As DWM_FRAME_COUNT
        Public cFramesDropped As DWM_FRAME_COUNT
        Public cFramesMissed As DWM_FRAME_COUNT
        Public cRefreshNextDisplayed As DWM_FRAME_COUNT
        Public cRefreshNextPresented As DWM_FRAME_COUNT
        Public cRefreshesDisplayed As DWM_FRAME_COUNT
        Public cRefreshesPresented As DWM_FRAME_COUNT
        Public cRefreshStarted As DWM_FRAME_COUNT
        Public cPixelsReceived As ULong
        Public cPixelsDrawn As ULong
        Public cBuffersEmpty As DWM_FRAME_COUNT
    End Structure

    Private Structure UNSIGNED_RATIO
        Public uiNumerator As UInt32
        Public uiDenominator As UInt32
    End Structure

    Private Structure QPC_TIME
        Public QPC_TIME As ULong
    End Structure

    Private Structure DWM_FRAME_COUNT
        Public DWM_FRAME_COUNT As ULong
    End Structure

    and am using it as:

    Private Sub Button5_Click(sender As System.Object, e As System.EventArgs) Handles Button5.Click
        Dim dwmInfo As DWM_TIMING_INFO
        Dim a As Integer = 0

        a = DwmGetCompositionTimingInfo(Me.Handle, dwmInfo)

End Sub

    but for all the DWM_TIMING_INFO structure I'm getting back all zeros.  I'm not quite sure what I'm doing wrong.  I'm really just looking for the refresh rate and vBlank time.

    Any help would be very much appreciated.


    • Edited by nmm2017 Friday, March 31, 2017 10:48 PM
    • Moved by Mattew Wu Monday, April 3, 2017 5:49 AM non Dev Center account issue
    Friday, March 31, 2017 10:45 PM

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