how to implement optical flow algorithm on ip camera feed

I have imported ip camera feed successfully in matlab by using below mentioned code.. but i m unable to implement optical flow algorithm for motion detection on it .. the optical flow algorithm is written to take video feed from webcam of my laptop.. i dont know how to change it so that it can take video feed from my ip camera... kindly help me out.

code used for importing ip cam feed :

url=('http://192.168.0.103:81/snapshot.jpg?user=admin&password=admin');
    hVideoIn = vision.VideoPlayer('Name', 'Final Video');
    while(1)
        ss=imread(url);
        step(hVideoIn,ss)
    end

optical flow algorithm:

vidDevice = imaq.VideoDevice('winvideo', 1, 'MJPG_320x240')
optical = vision.OpticalFlow( ...
    'OutputValue', 'Horizontal and vertical components in complex form');
maxWidth = imaqhwinfo(vidDevice,'MaxWidth');
maxHeight = imaqhwinfo(vidDevice,'MaxHeight');
shapes = vision.ShapeInserter;
shapes.Shape = 'Lines';
shapes.BorderColor = 'white';
r = 1:5:maxHeight;
c = 1:5:maxWidth;
[Y, X] = meshgrid(c,r);
hVideoIn = vision.VideoPlayer;
hVideoIn.Name  = 'Original Video';
hVideoOut = vision.VideoPlayer;
hVideoOut.Name  = 'Motion Detected Video';
% Set up for stream
nFrames = 0;
while (nFrames<1000)     % Process for the first 100 frames.
    % Acquire single frame from imaging device.
    rgbData = step(vidDevice);

      % Compute the optical flow for that particular frame.
      optFlow = step(optical,rgb2gray(rgbData));

      % Downsample optical flow field.
      optFlow_DS = optFlow(r, c);
      H = imag(optFlow_DS)*50;
      V = real(optFlow_DS)*50;

      % Draw lines on top of image
      lines = [Y(:)'; X(:)'; Y(:)'+V(:)'; X(:)'+H(:)'];
      rgb_Out = step(shapes, rgbData,  lines');

      % Send image data to video player
      % Display original video.
      step(hVideoIn, rgbData);
      % Display video along with motion vectors.
      step(hVideoOut, rgb_Out);

      % Increment frame count
      nFrames = nFrames + 1;
  end

[Nguyen Van Duong]

    % code
%Please download IP Camera Support from MATLAB
    % code
cam = ipcam('http://192.168.2.1/?action=stream');
optical = vision.OpticalFlow( ...
    'OutputValue', 'Horizontal and vertical components in complex form');
maxWidth = 640; %From your camera specs
maxHeight = 480; %From your camera specs
.
.
.
...
while (nFrames<100)     % Process for the first 100 frames.
    % Acquire single frame from imaging device.
    rgbData = snapshot(cam);
    rgbData = im2double(rgbData);