How to get a frame from output of STEP fuction

Hi,

I used vision.foreground to find the silhouette of moving person. Now I would like to make frame extraction for the output of this code but I dont know how to extract the window that result from step function.

another thing please, why ( out) and ( bbox) variables are zero when I implement the code.

videoSource = vision.VideoFileReader('person01_walking_d1_uncomp.avi','ImageColorSpace','Intensity','VideoOutputDataType','uint8');

detector = vision.ForegroundDetector(...
       'NumTrainingFrames', 500, ...
       'InitialVariance', 900);

     blob = vision.BlobAnalysis(...
         'CentroidOutputPort', false, 'AreaOutputPort', false, ...
         'BoundingBoxOutputPort', true, ...
         'MinimumBlobAreaSource', 'Property', 'MinimumBlobArea', 250);

     shapeInserter = vision.ShapeInserter('BorderColor','White');

     videoPlayer = vision.VideoPlayer();

while ~isDone(videoSource)
     frame  = step(videoSource);
     fgMask = step(detector, frame);
     bw2 = bwareaopen (fgMask, 250);

       bbox = step(blob, fgMask);

       out = step( shapeInserter, bw2,bbox);

       step (videoPlayer, out);

end

release(videoPlayer);
release(videoSource);

• _ I found the following code for extract frames from video but I dont know where should I put it exactly in the previous code._*

obj = VideoReader('person01_walking_d1_uncomp.avi');
for k = 1 : obj.NumberOfFrames  %fill in the appropriate number
  this_frame = read(obj, k);
  thisfig = figure();
  thisax = axes('Parent', thisfig);
  image(this_frame, 'Parent', thisax);
  title(thisax, sprintf('Frame #%d', k));
end

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HOW SHOULD I ASK TO BEEN ANSWERED ?

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IS THERE SOMETHING WRONG IN MY QUESTION ! :(