Silverlight 4 – Webcam Support

Author: Sumon Barua.

 

Silverlight 4 is now not only more mature but also came with rich features. Most of these features were recommendations from Silverlight community.

Webcam support is one of them. This was a very highly requested feature and has now been included in this version.

 

The following steps will get you up and running for the initial adventure:

Steps:

Step 1: First step is to get all the available capture devices(webcams, microphones etc) or default capture device on the system. So CaptureDeviceConfiguration class help us to obtain information about all available devices. This helper class exposes a number of static members for this purpose.

               CaptureDeviceConfiguration.GetAvailableVideoCaptureDevices()

-       It returns a collection of video devices on the system.

               CaptureDeviceConfiguration.GetAvailableAudioCaptureDevices()

-       All the audio devices.

               CaptureDeviceConfiguration.GetDefaultAudioCaptureDevice()

-       Default audio device.

               CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice()

-       Default video device.

So after the first step we got the device

Step 2: Before any interaction with the device, Silverlight application needs permission from the user(The user must grant permission in the security prompt and that way it ensures the call is safe).

               CaptureDeviceConfiguration.RequestDeviceAccess() : – To request access, call this static method in response to user initiated event like listbox item selection, button click etc. If your application automate this call without user interaction (i.e. Load event)  the method will return false and further action by application will throw an InvalidOperationException.

Okay application got the permission. Lets proceed for the next step

Step 3: Now we have permission and device handy. It’s time for the application to interact with the device using CaptureSource class. This class allows you to collect the video feed from the camera. To make this happen  create a CaptureSource object and set the VideoCaptureDevice to the selected device. With the help of CaptureSource the application is now capable of performing the following task on the devices

·         Start                                     

·         Stop

·         State of the device.

·         Capturing single video frame

 

Step 4: Now create a video brush. A VideoBrush gives us the ability to paint any area or controls with video content. At this stage we use CaptureSource as a  source of our brush

Step 5: The next thing we need to do is to call CaptureSource.Start() method to begin capturing our live video.

Step 6: Finally we’ll set the Fill property of a Rectangle object to this brush.

 

Simple application:

Now we will code a very simple application

1. Create a Silverlight application and open the MainPage.xaml

2. Add one rectangle(for display purpose) and two buttons(start and stop).

    <Grid x:Name="LayoutRoot" Background="White">

        <StackPanel Name="mainStackpanel">

            <Rectangle Height="256" Name="myDisplay" Stroke="Black" StrokeThickness="1" Width="584" />

            <StackPanel Name="subStackpanel" Orientation="Horizontal" HorizontalAlignment="Center">

                <Button x:Name="butStart" Content="Start" Click="butStart_Click"/>

                <Button x:Name="butStop" Content="Stop" Click="butStop_Click" />

            </StackPanel>

        </StackPanel>

    </Grid>

 

3.Code behind as follows

  public partial class MainPage : UserControl

    {

        CaptureSource captureSourec;

 

        public MainPage()

        {

            InitializeComponent();

 

        }

 

        private void butStart_Click(object sender, RoutedEventArgs e)

        {

            //Get the default video device

            VideoCaptureDevice myWebcam = CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();

           

            //Grant permission

            if (CaptureDeviceConfiguration.AllowedDeviceAccess ||

                                           CaptureDeviceConfiguration.RequestDeviceAccess())

            {

               

                captureSourec = new CaptureSource();

                captureSourec.VideoCaptureDevice  = myWebcam;

               

                //Create video brush that will get feed from captureSourec

                VideoBrush myBrush = new VideoBrush();

                myBrush.SetSource(captureSourec);

                myBrush.Stretch = Stretch.UniformToFill;

 

 

                //Stat the web cam

                captureSourec.Start();

 

                //Now display through the Rectangle

                myDisplay.Fill = myBrush;

 

 

            }

        }

 

 

        private void butStop_Click(object sender, RoutedEventArgs e)

        {

            if (captureSourec != null)

            {

                captureSourec.Stop();

            }

        }

    }

 

 

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