Using third-party filters in a video application in C#

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Runtime.InteropServices;

using DirectShowLib;

namespace CsVidSeg
{
  /// <summary>
  /// Summary description for Form1.
  /// </summary>
  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.GroupBox groupBox1;
    private System.Windows.Forms.TrackBar trackBar1;
    private System.Windows.Forms.Panel panel1;
    private System.Windows.Forms.Button buttonPlay;
    private System.Windows.Forms.Button buttonPause;
    private System.Windows.Forms.Button buttonStop;
    private System.Windows.Forms.Button buttonFramestep;
    private System.Windows.Forms.Button buttonLoop;

    // some variables 
    bool bLoop = false; 
    bool canStep = false;
    int minutes, seconds;
    string fileName;

    // filter graph and different interfaces
    FilterGraph fg = null;
    IGraphBuilder graphBuilder = null;
    IMediaControl mediaCtrl = null;
    IMediaEventEx mediaEvt = null;
    IMediaPosition mediaPos = null;
    IVideoFrameStep frameStep = null;
    IVideoWindow videoWin = null;
    IVideoWindow videoWin2 = null;

    // We'll use an Infinite Tee filter object to duplicate the
    // video stream by two
    InfTee tee = null;

    // We'll only treat wmv format 
    WMAsfReader reader =  null;

    // The Sobel object and filter interface
    object sobelObject = null;
    IBaseFilter sobel = null;
    // the black and white filter interface
    IBaseFilter bw = null;

    // the Guids for our custom filters
    Guid sobelGuid = new Guid( "1C826B9A-4008-4C41-B601-A783A40AFAB2" );
    Guid bwGuid = new Guid( "0C017086-684E-41c9-A4BB-640570C64B28" );

    // Some states variables, I could have used DSLib ones instead
    enum State { Playing, Paused, Stopped };
    State graphState;

    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.StatusBarPanel statusBarPanel1;
    private System.Windows.Forms.StatusBar statusBar1;
    private System.Windows.Forms.Panel panel2;
    private System.Windows.Forms.Label label2;
    private System.Windows.Forms.Button buttonOpen;
    private System.ComponentModel.IContainer components;

    public Form1()
    {
      //
      // Required for Windows Form Designer support
      //
      InitializeComponent();

      //
      // TODO: Add any constructor code after InitializeComponent call
      //
      trackBar1.Minimum = 0;
      trackBar1.Maximum = 256;
      trackBar1.Enabled = true;
      trackBar1.Value = 128;
      statusBar1.Panels[0].Text = "Duration: 00m:00s";
      fileName = "";
    }

    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    protected override void Dispose( bool disposing )
    {
      if( disposing )
      {
        if (components != null) 
        {
          components.Dispose();
        }
      }
      base.Dispose( disposing );
    }

        #region Windows Form Designer generated code
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
      this.groupBox1 = new System.Windows.Forms.GroupBox();
      this.label2 = new System.Windows.Forms.Label();
      this.label1 = new System.Windows.Forms.Label();
      this.trackBar1 = new System.Windows.Forms.TrackBar();
      this.buttonLoop = new System.Windows.Forms.Button();
      this.buttonFramestep = new System.Windows.Forms.Button();
      this.buttonStop = new System.Windows.Forms.Button();
      this.buttonPause = new System.Windows.Forms.Button();
      this.buttonPlay = new System.Windows.Forms.Button();
      this.panel1 = new System.Windows.Forms.Panel();
      this.statusBarPanel1 = new System.Windows.Forms.StatusBarPanel();
      this.statusBar1 = new System.Windows.Forms.StatusBar();
      this.panel2 = new System.Windows.Forms.Panel();
      this.buttonOpen = new System.Windows.Forms.Button();
      this.groupBox1.SuspendLayout();
      ((System.ComponentModel.ISupportInitialize)(this.trackBar1)).BeginInit();
      ((System.ComponentModel.ISupportInitialize)(this.statusBarPanel1)).BeginInit();
      this.SuspendLayout();
      // 
      // groupBox1
      // 
      this.groupBox1.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                            this.buttonOpen,
                                                                            this.label2,
                                                                            this.label1,
                                                                            this.trackBar1,
                                                                            this.buttonLoop,
                                                                            this.buttonFramestep,
                                                                            this.buttonStop,
                                                                            this.buttonPause,
                                                                            this.buttonPlay});
      this.groupBox1.Location = new System.Drawing.Point(8, 0);
      this.groupBox1.Name = "groupBox1";
      this.groupBox1.Size = new System.Drawing.Size(664, 88);
      this.groupBox1.TabIndex = 9;
      this.groupBox1.TabStop = false;
      // 
      // label2
      // 
      this.label2.Location = new System.Drawing.Point(256, 56);
      this.label2.Name = "label2";
      this.label2.Size = new System.Drawing.Size(88, 24);
      this.label2.TabIndex = 8;
      this.label2.Text = "Threshold";
      // 
      // label1
      // 
      this.label1.Location = new System.Drawing.Point(24, 56);
      this.label1.Name = "label1";
      this.label1.Size = new System.Drawing.Size(136, 23);
      this.label1.TabIndex = 7;
      this.label1.Text = "Treshold value: 128";
      // 
      // trackBar1
      // 
      this.trackBar1.AutoSize = false;
      this.trackBar1.Location = new System.Drawing.Point(344, 40);
      this.trackBar1.Name = "trackBar1";
      this.trackBar1.Size = new System.Drawing.Size(312, 45);
      this.trackBar1.TabIndex = 6;
      this.trackBar1.TickStyle = System.Windows.Forms.TickStyle.TopLeft;
      this.trackBar1.ValueChanged += new System.EventHandler(this.trackBar1_ValueChanged);
      // 
      // buttonLoop
      // 
      this.buttonLoop.Location = new System.Drawing.Point(560, 16);
      this.buttonLoop.Name = "buttonLoop";
      this.buttonLoop.Size = new System.Drawing.Size(88, 24);
      this.buttonLoop.TabIndex = 5;
      this.buttonLoop.Text = "Loop";
      this.buttonLoop.Click += new System.EventHandler(this.buttonLoop_Click);
      // 
      // buttonFramestep
      // 
      this.buttonFramestep.Enabled = false;
      this.buttonFramestep.Location = new System.Drawing.Point(448, 16);
      this.buttonFramestep.Name = "buttonFramestep";
      this.buttonFramestep.Size = new System.Drawing.Size(88, 24);
      this.buttonFramestep.TabIndex = 3;
      this.buttonFramestep.Text = "Framestep";
      this.buttonFramestep.Click += new System.EventHandler(this.buttonFramestep_Click);
      // 
      // buttonStop
      // 
      this.buttonStop.Location = new System.Drawing.Point(344, 16);
      this.buttonStop.Name = "buttonStop";
      this.buttonStop.Size = new System.Drawing.Size(88, 24);
      this.buttonStop.TabIndex = 2;
      this.buttonStop.Text = "Stop";
      this.buttonStop.Click += new System.EventHandler(this.buttonStop_Click);
      // 
      // buttonPause
      // 
      this.buttonPause.Location = new System.Drawing.Point(232, 16);
      this.buttonPause.Name = "buttonPause";
      this.buttonPause.Size = new System.Drawing.Size(88, 24);
      this.buttonPause.TabIndex = 1;
      this.buttonPause.Text = "Pause";
      this.buttonPause.Click += new System.EventHandler(this.buttonPause_Click);
      // 
      // buttonPlay
      // 
      this.buttonPlay.Location = new System.Drawing.Point(120, 16);
      this.buttonPlay.Name = "buttonPlay";
      this.buttonPlay.Size = new System.Drawing.Size(88, 24);
      this.buttonPlay.TabIndex = 0;
      this.buttonPlay.Text = "Play";
      this.buttonPlay.Click += new System.EventHandler(this.buttonPlay_Click);
      // 
      // panel1
      // 
      this.panel1.Location = new System.Drawing.Point(8, 104);
      this.panel1.Name = "panel1";
      this.panel1.Size = new System.Drawing.Size(320, 240);
      this.panel1.TabIndex = 4;
      // 
      // statusBarPanel1
      // 
      this.statusBarPanel1.Alignment = System.Windows.Forms.HorizontalAlignment.Center;
      this.statusBarPanel1.AutoSize = System.Windows.Forms.StatusBarPanelAutoSize.Contents;
      this.statusBarPanel1.Width = 10;
      // 
      // statusBar1
      // 
      this.statusBar1.Location = new System.Drawing.Point(0, 360);
      this.statusBar1.Name = "statusBar1";
      this.statusBar1.Panels.AddRange(new System.Windows.Forms.StatusBarPanel[] {
                                                                                  this.statusBarPanel1});
      this.statusBar1.ShowPanels = true;
      this.statusBar1.Size = new System.Drawing.Size(680, 22);
      this.statusBar1.SizingGrip = false;
      this.statusBar1.TabIndex = 6;
      // 
      // panel2
      // 
      this.panel2.Location = new System.Drawing.Point(352, 104);
      this.panel2.Name = "panel2";
      this.panel2.Size = new System.Drawing.Size(320, 240);
      this.panel2.TabIndex = 7;
      // 
      // buttonOpen
      // 
      this.buttonOpen.Location = new System.Drawing.Point(16, 16);
      this.buttonOpen.Name = "buttonOpen";
      this.buttonOpen.Size = new System.Drawing.Size(88, 24);
      this.buttonOpen.TabIndex = 0;
      this.buttonOpen.Text = "Open";
      this.buttonOpen.Click += new System.EventHandler(this.buttonOpen_Click);
      // 
      // Form1
      // 
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(680, 382);
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                  this.panel2,
                                                                  this.statusBar1,
                                                                  this.panel1,
                                                                  this.groupBox1});
      this.MaximizeBox = false;
      this.Name = "Form1";
      this.SizeGripStyle = System.Windows.Forms.SizeGripStyle.Hide;
      this.Text = "Video Segmentation in C#";
      this.groupBox1.ResumeLayout(false);
      ((System.ComponentModel.ISupportInitialize)(this.trackBar1)).EndInit();
      ((System.ComponentModel.ISupportInitialize)(this.statusBarPanel1)).EndInit();
      this.ResumeLayout(false);

    }
        #endregion

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main() 
    {
      Application.Run(new Form1());
    }

    // 
    //This method create the filter graph
    //
    void InitInterfaces() 
    {
      try 
      {   
        fg = new FilterGraph();
        graphBuilder = (IGraphBuilder) fg; 
        mediaCtrl = (IMediaControl) fg;
        mediaEvt = (IMediaEventEx) fg;
        mediaPos = (IMediaPosition) fg;
      }
      catch(Exception) 
      {
        MessageBox.Show( "Couldn't start" );
      }
    }  

    //
    //This method stop the filter graph and ensures that we stop
    //sending messages to our window
    //
    void CloseInterfaces() 
    {   
      if( mediaCtrl != null ) 
      {
        mediaCtrl.StopWhenReady();
        mediaEvt.SetNotifyWindow( (IntPtr)0, WM_GRAPHNOTIFY, (IntPtr)0 ); 
      }  
      mediaCtrl = null;
      mediaEvt = null;
      mediaPos = null;
      if( canStep )
        frameStep = null;
      videoWin = null;
      videoWin2 = null;
      if( fg != null ) 
        Marshal.ReleaseComObject(this.fg);
      fg = null;
    }   
  

    //
    // This method checks if a pin is processing a video stream
    //
    bool CheckVideo( IPin pin ) 
    {
      AMMediaType mt = new AMMediaType();
      mt.majorType = MediaType.Video;
      if( pin.QueryAccept( mt ) == 0 )
        return true;
      else
        return false;
    }

    //
    // This method find the second renderer in the filter graph;
    // it assumes that the first renderer had its "owner" property set
    //
    IVideoWindow GetSecondRenderer() 
    {
      IEnumFilters enumFilters;
      ArrayList filtersArray = new ArrayList();

      IFilterGraph filterGraph = (IFilterGraph)fg;
      filterGraph.EnumFilters(out enumFilters);
      
      IBaseFilter[] filters = new IBaseFilter[1];
      int fetched;

      while(enumFilters.Next(1, filters, out fetched) == 0)
      {
        IVideoWindow ivw = filters[0] as IVideoWindow;
        if( ivw != null ) 
        {
          IntPtr outPtr = new IntPtr();
          ivw.get_Owner( out outPtr );
          if( outPtr == IntPtr.Zero )
            return ivw;
        }
      }
      return null;
    }

    //
    //Method to start to play a media file
    //
    void LoadFile( string fName ) 
    {            
      try
      {
        // build the graph

        // create sobel filter
        Type t = Type.GetTypeFromCLSID( sobelGuid );
        sobelObject = Activator.CreateInstance( t );
        sobel = (IBaseFilter)sobelObject;        
        
        // create the black and white filter
        t = Type.GetTypeFromCLSID( bwGuid );
        bw = (IBaseFilter)Activator.CreateInstance( t );

        // create the infinite tee filter
        tee = new InfTee();

        // add all these filters to the graph
        graphBuilder.AddFilter( sobel, "Sobel" );
        graphBuilder.AddFilter( bw, "BW" );
        graphBuilder.AddFilter( (IBaseFilter)tee, "Tee" );

        // prepare our asf reader object
        reader = new WMAsfReader();
        ((IFileSourceFilter)reader).Load( fName, null );
        graphBuilder.AddFilter( (IBaseFilter)reader, "Reader" );

        // connect video source to infinite tee filter
        IPin teeInput = DsFindPin.ByDirection( (IBaseFilter)tee, PinDirection.Input, 0 );
        IPin vidOutput = DsFindPin.ByDirection( (IBaseFilter)reader, PinDirection.Output, 0 );
        // check if the video stream is on the first pin
        if( CheckVideo( vidOutput ) )
          graphBuilder.Connect( vidOutput, teeInput );
        else // video stream is on second pin
        {
          vidOutput = DsFindPin.ByDirection( (IBaseFilter)reader, PinDirection.Output, 1 );
          graphBuilder.Connect( vidOutput, teeInput );
        }

        // render output pin of tee
        IPin teeOutput = DsFindPin.ByDirection( (IBaseFilter)tee, PinDirection.Output, 0 );
        graphBuilder.Render( teeOutput );
        
        //check for the ability to step
        frameStep = fg as IVideoFrameStep;
        if( frameStep.CanStep( 1, null ) == 0 ) 
        {
          canStep = true;
          buttonFramestep.Enabled = true;
        }

        //prepare and set the first video window
        videoWin    = fg as IVideoWindow;
        videoWin.put_Owner( (IntPtr)panel2.Handle );
        videoWin.put_WindowStyle( WindowStyle.Child | WindowStyle.ClipSiblings | WindowStyle.ClipChildren );                
        Rectangle rc = panel2.ClientRectangle;
        videoWin.SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
        mediaEvt.SetNotifyWindow( (IntPtr)this.Handle, WM_GRAPHNOTIFY, (IntPtr)0 );
                
        // render original video from second output pin
        IPin teeOutput2 = DsFindPin.ByDirection( (IBaseFilter)tee, PinDirection.Output, 1 );
        graphBuilder.Render( teeOutput2 );

        // setup second video window 
        videoWin2 = GetSecondRenderer();
        if( videoWin2 != null ) 
        {
          videoWin2.put_Owner( (IntPtr)panel1.Handle );
          videoWin2.put_WindowStyle( WindowStyle.Child | WindowStyle.ClipSiblings | WindowStyle.ClipChildren );                
          rc = panel1.ClientRectangle;
          videoWin2.SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
        }

        //set the different values for controls
        Text = fName;    
        double duration;
        mediaPos.get_Duration( out duration);        
        trackBar1.Value = 128;
        minutes = (int)duration/60;
        seconds = (int)duration % 60;
        statusBar1.Panels[0].Text = "Duration: " + minutes.ToString( "D2" ) 
          + ":m" + seconds.ToString( "D2" ) + ":s" ;
        graphState = State.Playing;

        //DsROTEntry rot = new DsROTEntry( (IFilterGraph)fg );
        //start the playback
        mediaCtrl.Run();  
      } 
      catch( Exception ) { Text = "Error loading file"; }
    }   

    //different constant needed by the app
    const int WM_GRAPHNOTIFY    = 0x00008001;   
    const int WS_CHILD          = 0x40000000;
    const int WS_CLIPCHILDREN   = 0x02000000;
    const int WS_CLIPSIBLINGS   = 0x04000000;
    const int WM_MOVE           = 0x00000003;
    const int EC_COMPLETE       = 0x00000001;
  
    //
    //override to process custom graph notify messages
    //
    protected override void WndProc( ref Message m )
    {
      if( m.Msg == WM_GRAPHNOTIFY )
      {
        if( mediaEvt != null )
          OnGraphNotify();
        return;
      }
      base.WndProc( ref m );
    }

    //
    //call to process WM_GRAPHNOTIFY message
    //get out of the loop when GetEvent returns not 0
    //
    void OnGraphNotify()
    {
      int p1, p2;
      EventCode code;

      if( mediaEvt == null )
        return;
      while( mediaEvt.GetEvent( out code, out p1, out p2, 0 ) == 0 ) 
      {                             
        mediaEvt.FreeEventParams( code, p1, p2 );
        if( code == EventCode.Complete )
          OnClipCompleted();
      }
    }

    //
    //method that update the graph filter and/or gui controls
    //when we have received a message that the media file is done playing
    //
    void OnClipCompleted()
    {
      graphState = State.Stopped;
      if( mediaCtrl == null )
        return;
      mediaCtrl.Stop(); 
      if( bLoop ) 
      {
        mediaPos.put_CurrentPosition( 0.0 );
        mediaCtrl.Run();
      }
    }

    //
    // Display a dialog box to have the user chose a video file
    //
    private void buttonOpen_Click(object sender, System.EventArgs e)
    {
      // if the graph is not stopped, stop it now
      if( mediaCtrl != null && graphState != State.Stopped ) 
      {
        mediaCtrl.Stop();
        graphState = State.Stopped;        
      }
      OpenFileDialog ofd = new OpenFileDialog();
      ofd.Filter = "WMVideo (*.wmv)|*.wmv";
      if( ofd.ShowDialog() == DialogResult.OK ) 
      {
        CloseInterfaces();
        InitInterfaces();
        fileName = ofd.FileName;
        LoadFile( fileName );
      }
    }    

    //
    // if user clicks play then play video file or restart if stopped
    //
    private void buttonPlay_Click(object sender, System.EventArgs e)
    {
      if( mediaCtrl != null &&  graphState == State.Paused ) 
      {
        mediaCtrl.Run();
        graphState = State.Playing;
      }
      if( mediaCtrl != null &&  graphState == State.Stopped )
      {
        mediaCtrl.Stop(); 
        mediaPos.put_CurrentPosition( 0.0 );
        mediaCtrl.Run();
      }
    }

    //
    // pause button handler
    //
    private void buttonPause_Click(object sender, System.EventArgs e)
    {
      if( mediaCtrl != null && graphState != State.Paused ) 
      {
        mediaCtrl.Pause();
        graphState = State.Paused;
      }
    }

    //
    // stop button handler
    //
    private void buttonStop_Click(object sender, System.EventArgs e)
    {
      if( mediaCtrl != null && graphState != State.Stopped ) 
      {
        mediaCtrl.Stop();
        graphState = State.Stopped;        
      }
    } 

    //
    //when the user grabs the trackbar, we change the Sobel 
    //treshold value and step one frame (if possible) or run again
    //
    private void trackBar1_ValueChanged(object sender, System.EventArgs e)
    {
      if( mediaCtrl != null ) 
      {
        mediaCtrl.Pause();
        // access the ISobel interface on the sobel object
        ISobel isobel = sobelObject as ISobel;
        if( isobel != null ) 
        {
          isobel.SetThreshold( trackBar1.Value );
          label1.Text = "Treshold value: " + trackBar1.Value.ToString();
        }
        if( frameStep != null ) 
        {
          frameStep.Step( 1, null );
          graphState = State.Paused;
        }
        else
          mediaCtrl.Run();
      }
    }

    //
    // loop button handler
    private void buttonLoop_Click(object sender, System.EventArgs e)
    {
      bLoop = ! bLoop;
    }


    //
    // frame stepping handler
    //
    private void buttonFramestep_Click(object sender, System.EventArgs e)
    {
      if( frameStep != null ) 
      {
        mediaCtrl.Pause();
        graphState = State.Paused;
        frameStep.Step( 1, null );
      }       
    }
  }

  // 
  // The ISobel interface is a custom COM interface
  // exposed by the Sobel filter, in order to access it
  // from C#, we need to define it
  //
  [Guid("263AFD9E-465C-4dde-9BB1-168C25E2B87F"),
  InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
  public interface ISobel
  {
    int SetThreshold( int newValue );
  }

}