Question

How to capture a Webcam image from within my own application

Asked by: PantoffelSlippers

Hi experts,

I need to incorporate a window into an application that I'm writing that will capture an image from a Webcam connected to the computer running my application.

This should be possible via the DirectX/DirectDraw API or maybe even GDI within the .Net framework.

Please advise me on what is currently the best approach to take and how to get started with it.

I'm using Microsoft .Net Framework 3.5 for my application. If possible I'd like to use the same to get the image captured.

Thanks

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Asked On: 2009-05-31 at 07:42:29ID24451647
Tags: Webcam
,; DirectX
,; DirectDraw
,; GDI
,; GDI+
,; Graphics
,; Programming
,; API.Windows Programming
Topics: Windows Programming
,; .NET
,; Computer Web Cameras
Participating Experts: 3
Points: 500
Comments: 10

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Answers

by: knight00Posted on 2009-05-31 at 12:28:56ID: 24513613

This is one of the easier way to accomplish what you need

http://blogs.msdn.com/markhsch/archive/2007/11/19/c-webcam-user-control-source.aspx

by: PantoffelSlippersPosted on 2009-06-01 at 12:16:46ID: 24520767

Thanks - I'll take a look!

by: VegasCidPosted on 2009-06-01 at 16:26:15ID: 24522773

Using the example attached (I don't remember where I get it) I got create a xaml webcam viewer control like this (this code don't comple, is a part of a real application):

Probably code snipet is not the best example, but I get my aplication to work reading demo example programming with windows forms attached.

After a while testing and researching diferents options to capture a webcam when I had to do this the application attached was the best way to understand all of this world, for a begginer like me in that moment. It have a lot of option to configure webcam, get webcams in the system and more things.

Kind Regards

<UserControl x:Uid="UserControl_1" x:Class="IGC.UI.UserControls.ControlWebcamViewer"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:wpf="http://schemas.microsoft.com/netfx/2007/xaml/presentation"
    Height="Auto" Width="Auto">
    <Grid x:Uid="LayoutRoot" x:Name="LayoutRoot" Height="auto" Width="auto">
        <Viewbox x:Uid="Viewbox" x:Name="Viewbox" Margin="0,0,0,0" VerticalAlignment="Stretch" Height="Auto" Stretch="Fill">
            <wpf:WindowsFormsHost x:Uid="wfh" xmlns:my="clr-namespace:System.Windows.Forms.Integration;assembly=WindowsFormsIntegration"  x:Name="wfh" Margin="0,0,0,0"  Width="90" Height="60">
            </wpf:WindowsFormsHost>
        </Viewbox>
    </Grid>
</UserControl>
 
 
 
 
CodeBehind:
 
 
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
 
using System.Threading;
using Assergs.Windows.Controls;
using System.IO;
using System.Data;
using System.Net;
 
using System.Windows.Media.Animation;
using System.Windows.Forms.Integration;
using System.Reflection;
 
namespace IGC.UI.UserControls
{
    /// <summary>
    /// Interaction logic for ControlWebcamViewer.xaml
    /// </summary>
    public partial class ControlWebcamViewer : UserControl
    {
        public bool isActive = false;
        public DirectX.Capture.Capture capt = null;
        
        public ControlWebcamViewer()
        {
            
            InitializeComponent();
        }
 
        protected override void OnChildDesiredSizeChanged(UIElement child)
        {
            base.OnChildDesiredSizeChanged(child);
            child.RenderSize = new Size(((Viewbox.ActualWidth * 240) / 320), Viewbox.ActualWidth);
        }
 
        public void start(DirectX.Capture.Filter _video)
        {
            
 
             if (capt == null)
             {
                 capt = new DirectX.Capture.Capture(_video, null);
 
                 wfh.Child = new System.Windows.Forms.Panel();
                 capt.PreviewWindow = wfh.Child;
             }
             else
             {
                 if (capt != null && capt.PreviewWindow == null )
                 {
                     capt.PreviewWindow = wfh.Child;
                 }
                 System.Windows.Forms.Control oldPreview = capt.PreviewWindow;
                 capt.PreviewWindow = null;
                 capt = new DirectX.Capture.Capture(_video, null);
                 capt.PreviewWindow = oldPreview;
                 wfh.Child = capt.PreviewWindow;
                 isActive = true;
             }
        }
 
        public void stop()
        {
            if(capt != null)
                capt.PreviewWindow = null;
        }
        
        public void wfhSizeChanged(double w)
        {
            wfh.Height = ((w * 240) / 320);
            if (wfh.Child != null)
            {
                wfh.Child.Height = (int)wfh.Height;
                wfh.Child.Size = new System.Drawing.Size((int)w, (int)(wfh.Height));
            }
            //wfh.Height = (int)((Viewbox.ActualWidth * 240) / 320);
            //if (wfh.Child != null)
            //{
            //    wfh.Child.Height = (int)((Viewbox.ActualWidth * 240) / 320);
            //    wfh.Child.Size = new System.Drawing.Size((int)Viewbox.ActualWidth, (int)((Viewbox.ActualWidth * 240) / 320));
            //}
        }
 
        public Size tamanio()
        {
            return new Size(Viewbox.Width, wfh.Height);
        }
    }
}
 
// I use it with:
 <IGC.UserControl:ControlWebcamViewer x:Name="webcamControlViewer1" HorizontalContentAlignment="Stretch">
</IGC.UserControl:ControlWebcamViewer>
 
string codec = (string)(WebcamControlConfig.SelectedValue as ListBoxItem).Content;
                if (!codec.Equals("Don't selected"))
                {
                    if (filters != null)
                        foreach (DirectX.Capture.Filter var in filters.VideoInputDevices)
                        {
                            if (var.Name == codec)
                            {
                                _video = var;
                                break;
                            }
                        }
                    webcamControlViewer1.start(_video);
                }
 
 
 public void loadwebcams(ComboBox combo)
        {
            combo.Items.Clear();
 
            ListBoxItem m = new ListBoxItem();
 
            m.Content = "No Seleccionada";
            combo.Items.Add(m);
 
            if (filters == null)
            {
                try
                {
                    filters = new DirectX.Capture.Filters();
                }
                catch (Exception ex)
                {
                    System.Windows.MessageBox.Show(ex.Message, "Webcam");
                }
            }
 
            if (filters != null)
                foreach (DirectX.Capture.Filter var in filters.VideoInputDevices)
                {
                    ListBoxItem lbi = new ListBoxItem();
                    lbi.Content = var.Name;
                    combo.Items.Add(lbi);
                }
        }

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Select all Open in new window

by: VegasCidPosted on 2009-06-01 at 16:29:35ID: 24522799

I have found the webpage where I got it because I can't attach a rar file with entire solution

http://www.codeproject.com/KB/directx/directxcapture.aspx?display=PrintAll&fid=14156&df=90&mpp=25&noise=3&sort=Position&view=Quick&fr=251

by: PantoffelSlippersPosted on 2009-06-01 at 23:03:22ID: 24524190

Thanks!!!!!

by: PantoffelSlippersPosted on 2009-06-01 at 23:06:44ID: 24524197

VegasCid,

I imagine that I'll be able to use the same classes more or less to capture a picture from a Webcam instead of capturing vidio from a capture card right?

Thanks

by: VegasCidPosted on 2009-06-02 at 01:12:51ID: 24524591

I don't remember how do it exactly, but yes you can take pictures. I think but I'm not sure you can use previewCapt

by: knight00Posted on 2009-06-03 at 06:57:37ID: 24536570

The following code has everything you need. Just reference the DShow.NET library and call the btnTakePhoto_Click method to take the picture.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
 
using DShowNET;
using DShowNET.Device;
using System.Collections;
using System.Drawing.Imaging;
using System.IO;
 
namespace Webcam
{
    public partial class FormCamera : Form, ISampleGrabberCB
    {
        /// <summary> flag to detect first Form appearance </summary>
        private bool firstActive;
 
        /// <summary> base filter of the actually used video devices. </summary>
        private IBaseFilter capFilter;
 
        /// <summary> graph builder interface. </summary>
        private IGraphBuilder graphBuilder;
 
        /// <summary> capture graph builder interface. </summary>
        private ICaptureGraphBuilder2 capGraph;
        private ISampleGrabber sampGrabber;
 
        /// <summary> control interface. </summary>
        private IMediaControl mediaCtrl;
 
        /// <summary> event interface. </summary>
        private IMediaEventEx mediaEvt;
 
        /// <summary> video window interface. </summary>
        private IVideoWindow videoWin;
 
        /// <summary> grabber filter interface. </summary>
        private IBaseFilter baseGrabFlt;
 
        /// <summary> structure describing the bitmap to grab. </summary>
        private VideoInfoHeader videoInfoHeader;
        private bool captured = true;
        private int bufferedSize;
 
        /// <summary> buffer for bitmap data. </summary>
        private byte[] savedArray;
 
        /// <summary> list of installed video devices. </summary>
        private ArrayList capDevices;
 
        private const int WM_GRAPHNOTIFY = 0x00008001;	// message from graph
 
        private const int WS_CHILD = 0x40000000;	// attributes for video window
        private const int WS_CLIPCHILDREN = 0x02000000;
        private const int WS_CLIPSIBLINGS = 0x04000000;
 
        /// <summary> event when callback has finished (ISampleGrabberCB.BufferCB). </summary>
        private delegate void CaptureDone();
 
#if DEBUG
        private int rotCookie = 0;
#endif
 
        private void btnTakePhoto_Click(object sender, EventArgs e)
        {
            int hr;
            if (sampGrabber == null)
                return;
            Trace.WriteLine("!!BTN: toolBarBtnGrab");
 
            if (savedArray == null)
            {
                int size = videoInfoHeader.BmiHeader.ImageSize;
                if ((size < 1000) || (size > 16000000))
                    return;
                savedArray = new byte[size + 64000];
            }
 
            pictureBox.Image = null;
            captured = false;
            hr = sampGrabber.SetCallback(this, 1);
        }
 
        private void FormCamera_FormClosing(object sender, FormClosingEventArgs e)
        {
            CloseInterfaces();
        }
 
        private void FormCamera_Activated(object sender, EventArgs e)
        {
            if (firstActive)
                return;
            firstActive = true;
 
            if (!DsUtils.IsCorrectDirectXVersion())
            {
                MessageBox.Show(this, "DirectX 8.1 NOT installed!", "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                this.Close(); return;
            }
 
            if (!DsDev.GetDevicesOfCat(FilterCategory.VideoInputDevice, out capDevices))
            {
                MessageBox.Show(this, "No video capture devices found!", "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                this.Close(); return;
            }
 
            DsDevice dev = null;
            dev = capDevices[0] as DsDevice;
 
            if (dev == null)
            {
                this.Close(); return;
            }
 
            if (!StartupVideo(dev.Mon))
                this.Close();
        }
 
        private void videoPanel_Resize(object sender, EventArgs e)
        {
            ResizeVideoWindow();
        }
 
        /// <summary> capture event, triggered by buffer callback. </summary>
        void OnCaptureDone()
        {
            Trace.WriteLine("!!DLG: OnCaptureDone");
            try
            {
                int hr;
                if (sampGrabber == null)
                    return;
                hr = sampGrabber.SetCallback(null, 0);
 
                int w = videoInfoHeader.BmiHeader.Width;
                int h = videoInfoHeader.BmiHeader.Height;
                if (((w & 0x03) != 0) || (w < 32) || (w > 4096) || (h < 32) || (h > 4096))
                    return;
                int stride = w * 3;
 
                GCHandle handle = GCHandle.Alloc(savedArray, GCHandleType.Pinned);
                int scan0 = (int)handle.AddrOfPinnedObject();
                scan0 += (h - 1) * stride;
                Bitmap b = new Bitmap(w, h, -stride, PixelFormat.Format24bppRgb, (IntPtr)scan0);
                handle.Free();
                savedArray = null;
                pictureBox.Image = b;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not grab picture\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
            }
        }
	    
        /// <summary> start all the interfaces, graphs and preview window. </summary>
        bool StartupVideo(UCOMIMoniker mon)
        {
            int hr;
            try
            {
                if (!CreateCaptureDevice(mon))
                    return false;
 
                if (!GetInterfaces())
                    return false;
 
                if (!SetupGraph())
                    return false;
 
                if (!SetupVideoWindow())
                    return false;
 
#if DEBUG
                DsROT.AddGraphToRot(graphBuilder, out rotCookie);		// graphBuilder capGraph
#endif
 
                hr = mediaCtrl.Run();
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                bool hasTuner = DsUtils.ShowTunerPinDialog(capGraph, capFilter, this.Handle);
 
                return true;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not start video stream\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                return false;
            }
        }
 
        /// <summary> make the video preview window to show in videoPanel. </summary>
        bool SetupVideoWindow()
        {
            int hr;
            try
            {
                // Set the video window to be a child of the main window
                hr = videoWin.put_Owner(videoPanel.Handle);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                // Set video window style
                hr = videoWin.put_WindowStyle(WS_CHILD | WS_CLIPCHILDREN);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                // Use helper function to position video window in client rect of owner window
                ResizeVideoWindow();
 
                // Make the video window visible, now that it is properly positioned
                hr = videoWin.put_Visible(DsHlp.OATRUE);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                hr = mediaEvt.SetNotifyWindow(this.Handle, WM_GRAPHNOTIFY, IntPtr.Zero);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
                return true;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not setup video window\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                return false;
            }
        }
 
        /// <summary> build the capture graph for grabber. </summary>
        bool SetupGraph()
        {
            int hr;
            try
            {
                hr = capGraph.SetFiltergraph(graphBuilder);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                hr = graphBuilder.AddFilter(capFilter, "Ds.NET Video Capture Device");
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                //DsUtils.ShowCapPinDialog(capGraph, capFilter, this.Handle);
 
                AMMediaType media = new AMMediaType();
                media.majorType = MediaType.Video;
                media.subType = MediaSubType.RGB24;
                media.formatType = FormatType.VideoInfo;		// ???
                hr = sampGrabber.SetMediaType(media);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                hr = graphBuilder.AddFilter(baseGrabFlt, "Ds.NET Grabber");
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                Guid cat = PinCategory.Preview;
                Guid med = MediaType.Video;
                hr = capGraph.RenderStream(ref cat, ref med, capFilter, null, null); // baseGrabFlt 
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                cat = PinCategory.Capture;
                med = MediaType.Video;
                hr = capGraph.RenderStream(ref cat, ref med, capFilter, null, baseGrabFlt); // baseGrabFlt 
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                media = new AMMediaType();
                hr = sampGrabber.GetConnectedMediaType(media);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
                if ((media.formatType != FormatType.VideoInfo) || (media.formatPtr == IntPtr.Zero))
                    throw new NotSupportedException("Unknown Grabber Media Format");
 
                videoInfoHeader = (VideoInfoHeader)Marshal.PtrToStructure(media.formatPtr, typeof(VideoInfoHeader));
                Marshal.FreeCoTaskMem(media.formatPtr); media.formatPtr = IntPtr.Zero;
 
                hr = sampGrabber.SetBufferSamples(false);
                if (hr == 0)
                    hr = sampGrabber.SetOneShot(false);
                if (hr == 0)
                    hr = sampGrabber.SetCallback(null, 0);
                if (hr < 0)
                    Marshal.ThrowExceptionForHR(hr);
 
                return true;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not setup graph\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                return false;
            }
        }
 
        /// <summary> create the used COM components and get the interfaces. </summary>
        bool GetInterfaces()
        {
            Type comType = null;
            object comObj = null;
            try
            {
                comType = Type.GetTypeFromCLSID(Clsid.FilterGraph);
                if (comType == null)
                    throw new NotImplementedException(@"DirectShow FilterGraph not installed/registered!");
                comObj = Activator.CreateInstance(comType);
                graphBuilder = (IGraphBuilder)comObj; comObj = null;
 
                Guid clsid = Clsid.CaptureGraphBuilder2;
                Guid riid = typeof(ICaptureGraphBuilder2).GUID;
                comObj = DsBugWO.CreateDsInstance(ref clsid, ref riid);
                capGraph = (ICaptureGraphBuilder2)comObj; comObj = null;
 
                comType = Type.GetTypeFromCLSID(Clsid.SampleGrabber);
                if (comType == null)
                    throw new NotImplementedException(@"DirectShow SampleGrabber not installed/registered!");
                comObj = Activator.CreateInstance(comType);
                sampGrabber = (ISampleGrabber)comObj; comObj = null;
 
                mediaCtrl = (IMediaControl)graphBuilder;
                videoWin = (IVideoWindow)graphBuilder;
                mediaEvt = (IMediaEventEx)graphBuilder;
                baseGrabFlt = (IBaseFilter)sampGrabber;
                return true;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not get interfaces\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                return false;
            }
            finally
            {
                if (comObj != null)
                    Marshal.ReleaseComObject(comObj); comObj = null;
            }
        }
 
        /// <summary> create the user selected capture device. </summary>
        bool CreateCaptureDevice(UCOMIMoniker mon)
        {
            object capObj = null;
            try
            {
                Guid gbf = typeof(IBaseFilter).GUID;
                mon.BindToObject(null, null, ref gbf, out capObj);
                capFilter = (IBaseFilter)capObj; capObj = null;
                return true;
            }
            catch (Exception ee)
            {
                MessageBox.Show(this, "Could not create capture device\r\n" + ee.Message, "DirectShow.NET", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                return false;
            }
            finally
            {
                if (capObj != null)
                    Marshal.ReleaseComObject(capObj); capObj = null;
            }
 
        }
 
        /// <summary> do cleanup and release DirectShow. </summary>
        void CloseInterfaces()
        {
            int hr;
            try
            {
#if DEBUG
                if (rotCookie != 0)
                    DsROT.RemoveGraphFromRot(ref rotCookie);
#endif
 
                if (mediaCtrl != null)
                {
                    hr = mediaCtrl.Stop();
                    mediaCtrl = null;
                }
 
                if (mediaEvt != null)
                {
                    hr = mediaEvt.SetNotifyWindow(IntPtr.Zero, WM_GRAPHNOTIFY, IntPtr.Zero);
                    mediaEvt = null;
                }
 
                if (videoWin != null)
                {
                    hr = videoWin.put_Visible(DsHlp.OAFALSE);
                    hr = videoWin.put_Owner(IntPtr.Zero);
                    videoWin = null;
                }
 
                baseGrabFlt = null;
                if (sampGrabber != null)
                    Marshal.ReleaseComObject(sampGrabber); sampGrabber = null;
 
                if (capGraph != null)
                    Marshal.ReleaseComObject(capGraph); capGraph = null;
 
                if (graphBuilder != null)
                    Marshal.ReleaseComObject(graphBuilder); graphBuilder = null;
 
                if (capFilter != null)
                    Marshal.ReleaseComObject(capFilter); capFilter = null;
 
                if (capDevices != null)
                {
                    foreach (DsDevice d in capDevices)
                        d.Dispose();
                    capDevices = null;
                }
            }
            catch (Exception)
            { }
        }
 
        /// <summary> resize preview video window to fill client area. </summary>
        void ResizeVideoWindow()
        {
            if (videoWin != null)
            {
                Rectangle rc = videoPanel.ClientRectangle;
                videoWin.SetWindowPosition(0, 0, rc.Right, rc.Bottom);
            }
        }
 
        /// <summary> override window fn to handle graph events. </summary>
        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_GRAPHNOTIFY)
            {
                if (mediaEvt != null)
                    OnGraphNotify();
                return;
            }
            base.WndProc(ref m);
        }
 
        /// <summary> graph event (WM_GRAPHNOTIFY) handler. </summary>
        void OnGraphNotify()
        {
            DsEvCode code;
            int p1, p2, hr = 0;
            do
            {
                hr = mediaEvt.GetEvent(out code, out p1, out p2, 0);
                if (hr < 0)
                    break;
                hr = mediaEvt.FreeEventParams(code, p1, p2);
            }
            while (hr == 0);
        }
 
 
        #region ISampleGrabberCB Members
 
        /// <summary> sample callback, NOT USED. </summary>
        int ISampleGrabberCB.SampleCB(double SampleTime, IMediaSample pSample)
        {
            Trace.WriteLine("!!CB: ISampleGrabberCB.SampleCB");
            return 0;
        }
 
        /// <summary> buffer callback, COULD BE FROM FOREIGN THREAD. </summary>
        int ISampleGrabberCB.BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
        {
            if (captured || (savedArray == null))
            {
                Trace.WriteLine("!!CB: ISampleGrabberCB.BufferCB");
                return 0;
            }
 
            captured = true;
            bufferedSize = BufferLen;
            Trace.WriteLine("!!CB: ISampleGrabberCB.BufferCB  !GRAB! size = " + BufferLen.ToString());
            if ((pBuffer != IntPtr.Zero) && (BufferLen > 1000) && (BufferLen <= savedArray.Length))
                Marshal.Copy(pBuffer, savedArray, 0, BufferLen);
            else
                Trace.WriteLine("    !!!GRAB! failed ");
            this.BeginInvoke(new CaptureDone(this.OnCaptureDone));
            return 0;
        }
 
        #endregion
    }
 
    internal enum PlayState
    {
        Init, Stopped, Paused, Running
    }
}

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Select all Open in new window

by: PantoffelSlippersPosted on 2009-08-15 at 05:30:36ID: 31587124

Many Many Thanks

by: Robert-OBPosted on 2010-02-04 at 10:44:38ID: 26488136

I've recreated this solution in VS2008, Windows 7 x64. The app during loading is struck in an infinite loop at this point (it appears that it never hits OnGraphNotify()):

/// <summary> override window fn to handle graph events. </summary>
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_GRAPHNOTIFY)
{
if (mediaEvt != null)
OnGraphNotify();
return;
}
base.WndProc(ref m);
}

20120131-EE-VQP-002

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