Question

I am simply trying to query the WP7 device’s camera resolutions, and add these resolutions to a ListPicker so that a user may choose the resolution that he or she desires for a videobrush. My videobrush is displayed on my MainPage, and the resolutions ListPicker is on my SettingsPage, so I will also need to pass this value from the SettingsPage to the MainPage so that the chosen resolution will be applied properly. So far what I have is as follows, although I am unsure of how to get the resolutions and add them to the ListPicker and then pass this value to be used in the MainPage?

MainPage.xaml

<Border x:Name="videoRectangle" Grid.Row="0" Grid.ColumnSpan="2" >
            <Border.Background>
                <VideoBrush  x:Name="viewfinderBrush">
                    <VideoBrush.RelativeTransform>
                        <CompositeTransform x:Name="viewfinderBrushTransform" CenterX=".5" CenterY=".5" Rotation="90" />
                    </VideoBrush.RelativeTransform>
                </VideoBrush>
            </Border.Background>
 </Border>

MainPage.xaml.cs

#region Fields
    //Declare a field of type PhotoCamera that will hold a reference to the camera
    private PhotoCamera camera;        

    #endregion

    #region Ctr

    // Constructor
    public MainPage()
    {
        InitializeComponent();
    }

    #endregion

    #region Navigation

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        //if camera = null {  .. } <-- is this necessary beforehand?
        // Check to see if the camera is available on the device.
        if ((PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == true) ||
             (PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) == true))
        {
            // Initialize the camera, when available.
            if (PhotoCamera.IsCameraTypeSupported(CameraType.Primary))
            {
                // Use front-facing camera if available.
                camera = new PhotoCamera(CameraType.Primary);

                camera.Initialized += camera_Initialized;
                viewfinderBrush.SetSource(camera);
            }
            else
            {
                // The Primary camera is not supported on the device.
                this.Dispatcher.BeginInvoke(delegate()
                {
                    // Write message.
                    MessageBox.Show("Primary camera is not available on this device.", "Error!", MessageBoxButton.OK);
                });
            }
        }
        else
        {
            // No camera is supported on the device.
            //this.Dispatcher.BeginInvoke(delegate()
            //{
                // Write message.
                MessageBox.Show("Primary camera is available on this device.", "Error!", MessageBoxButton.OK);
            //});
        }

        base.OnNavigatedTo(e);
    }

    protected override void OnNavigatedFrom(NavigationEventArgs e)
    {
        if (camera != null)
        {
            camera.Dispose();
            camera.Initialized -= camera_Initialized;
            camera = null;
        }

        base.OnNavigatedFrom(e);
    }

    #endregion

    void camera_Initialized(object sender, CameraOperationCompletedEventArgs e)
    {
        if (e.Succeeded)
        {
            //var res = from resolution in camera.AvailableResolutions
            //          //change to best resolution on camera
            //          //http://msdn.microsoft.com/en-us/library/hh202951(v=VS.92).aspx
            //          where resolution.Width == 640
            //          select resolution;

            //camera.Resolution = res.First();

            //***apply camera resolution here!?

            this.Dispatcher.BeginInvoke(delegate()
            {
                ShowRegularVideo();
            });
        }

        //throw new NotImplementedException();
    }

    private void ShowRegularVideo()
    {
        videoRectangle.Width = this.ActualWidth;
        videoRectangle.Height = this.ActualHeight;
    }

SettingsPage.xaml

<toolkit:ListPicker x:Name="ResolutionListPicker" Header="Resolutions" Grid.Row="3" Grid.ColumnSpan="2"                                            
                                        SelectedIndex="{Binding}"
                                        SelectionChanged="ResolutionListPicker_SelectionChanged"/>

SettingsPage.xaml.cs

#region Fields

    //Declare a field of type PhotoCamera that will hold a reference to the camera
    private PhotoCamera camera; 

    List<int> resolutionsList;

    #endregion

    #region Ctr

    public Settings()
    {
        InitializeComponent();
    }

    #endregion

    #region Navigation

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        base.OnNavigatedTo(e);

        GetResolutions();
    }

    protected override void OnNavigatedFrom(NavigationEventArgs e)
    {
        base.OnNavigatedFrom(e);
    }

    #endregion

    private void GetResolutions()
    {
        resolutionsList = new List<int>();

        //var res = from resolution in camera.AvailableResolutions
        //          //change to best resolution on camera
        //          //http://msdn.microsoft.com/en-us/library/hh202951(v=VS.92).aspx
        //          where resolution.Width == 640
        //          select resolution;

        //camera.Resolution = res.First();

        for (int i = 0; i < camera.AvailableResolutions.Count(); i++)
        {
            //resolutionsList.Add(...)
        }
    }

Answer 1

I think you started with How to: Create a Base Camera Application for Windows Phone
http://msdn.microsoft.com/en-us/library/hh202956(v=vs.92).aspx

if you look at the Res button, it shows you how to change resolution. If not have a look at How to: Adjust Captured Picture Resolution in an Application for Windows Phone
http://msdn.microsoft.com/en-us/library/hh202951(v=vs.92).aspx

Camera.AvailableResolutions
http://msdn.microsoft.com/en-us/library/microsoft.devices.camera.availableresolutions(v=vs.92).aspx

Resolutions are a collection of Size structures. Each Size specifies a Height and Width property.
Pixelcount = Height x Width

Then you divide it to get Kilo pixel or Mega pixel by dividing appropriately with 1024