Accord.Video.VFW.AVIReader.GetNextFrame C# (CSharp) Method

        public Bitmap GetNextFrame( )
        {
            lock ( sync )
            {
                if ( file == IntPtr.Zero )
                {
                    throw new System.IO.IOException( "Cannot read video frames since video file is not open." );
                }

                // get frame at specified position
                IntPtr DIB = Win32.AVIStreamGetFrame( getFrame, position );
                if ( DIB == IntPtr.Zero )
                    throw new VideoException( "Failed getting frame." );

                Win32.BITMAPINFOHEADER bitmapInfoHeader;

                // copy BITMAPINFOHEADER from unmanaged memory
                bitmapInfoHeader = (Win32.BITMAPINFOHEADER) Marshal.PtrToStructure( DIB, typeof( Win32.BITMAPINFOHEADER ) );

                // create new bitmap
                Bitmap image = new Bitmap( width, height, PixelFormat.Format24bppRgb );

                // lock bitmap data
                BitmapData imageData = image.LockBits(
                    new Rectangle( 0, 0, width, height ),
                    ImageLockMode.ReadWrite,
                    PixelFormat.Format24bppRgb );

                // copy image data
                int srcStride = imageData.Stride;
                int dstStride = imageData.Stride;

                // check image direction
                if ( bitmapInfoHeader.height > 0 )
                {
                    // it`s a bottom-top image
                    int dst = imageData.Scan0.ToInt32( ) + dstStride * ( height - 1 );
                    int src = DIB.ToInt32( ) + Marshal.SizeOf( typeof( Win32.BITMAPINFOHEADER ) );

                    for ( int y = 0; y < height; y++ )
                    {
                        Win32.memcpy( dst, src, srcStride );
                        dst -= dstStride;
                        src += srcStride;
                    }
                }
                else
                {
                    // it`s a top bootom image
                    int dst = imageData.Scan0.ToInt32( );
                    int src = DIB.ToInt32( ) + Marshal.SizeOf( typeof( Win32.BITMAPINFOHEADER ) );

                    // copy the whole image
                    Win32.memcpy( dst, src, srcStride * height );
                }

                // unlock bitmap data
                image.UnlockBits( imageData );

                // move position to the next frame
                position++;

                return image;
            }
        }
    }

        /// <summary>
        /// Worker thread.
        /// </summary>
        /// 
        private void WorkerThread( )
		{
            ReasonToFinishPlaying reasonToStop = ReasonToFinishPlaying.StoppedByUser;
            // AVI reader
			AVIReader aviReader = new AVIReader( );

			try
			{
				// open file
				aviReader.Open( source );

                // stop positions
                int stopPosition = aviReader.Start + aviReader.Length;

                // frame interval
                int interval = ( frameIntervalFromSource ) ? (int) ( 1000 / aviReader.FrameRate ) : frameInterval;

                while ( !stopEvent.WaitOne( 0, false ) )
				{
					// start time
					DateTime start = DateTime.Now;

					// get next frame
					Bitmap bitmap = aviReader.GetNextFrame( );

					framesReceived++;
                    bytesReceived += bitmap.Width * bitmap.Height *
                        ( Bitmap.GetPixelFormatSize( bitmap.PixelFormat ) >> 3 );

					if ( NewFrame != null )
						NewFrame( this, new NewFrameEventArgs( bitmap ) );

					// free image
					bitmap.Dispose( );

                    // check current position
                    if ( aviReader.Position >= stopPosition )
                    {
                        reasonToStop = ReasonToFinishPlaying.EndOfStreamReached;
                        break;
                    }

                    // wait for a while ?
                    if ( interval > 0 )
                    {
                        // get frame extract duration
                        TimeSpan span = DateTime.Now.Subtract( start );

                        // miliseconds to sleep
                        int msec = interval - (int) span.TotalMilliseconds;

                        if ( ( msec > 0 ) && ( stopEvent.WaitOne( msec, false ) ) )
                            break;
                    }
				}
			}
			catch ( Exception exception )
			{
                // provide information to clients
                if ( VideoSourceError != null )
                {
                    VideoSourceError( this, new VideoSourceErrorEventArgs( exception.Message ) );
                }
			}

			aviReader.Dispose( );
			aviReader = null;

            if ( PlayingFinished != null )
            {
                PlayingFinished( this, reasonToStop );
            } 
		}