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    <p><strong>Case 1 - If camera static</strong></p> <p>If the camera is static, it is really simple to track one person.</p> <p>You can apply a method called background subtraction. </p> <ol> <li><p>Here, for better results, you need a bare image from camera, with no persons in it. It is the background. ( It can also be done, even if you don't have this background image. But if you have it, better. I will tell at end what to do if no background image)</p></li> <li><p>Now start capture from camera. Take first frame,convert both to grayscale, smooth both images to avoid noise.</p></li> <li><p>Subtract background image from frame. </p></li> <li><p>If the frame has no change wrt background image (ie no person), you get a black image ( Of course there will be some noise, we can remove it). If there is change, ie person walked into frame, you will get an image with person and background as black.</p></li> <li><p>Now threshold the image for a suitable value.</p></li> <li><p>Apply some erosion to remove small granular noise. Apply dilation after that.</p></li> <li><p>Now find contours. Most probably there will be one contour,ie the person. </p></li> <li><p>Find centroid or whatever you want for this person to track. </p></li> </ol> <p>Now suppose you don't have a background image, you can find it using <a href="http://opencv.willowgarage.com/documentation/c/imgproc_motion_analysis_and_object_tracking.html?highlight=cvrunningavg#runningavg" rel="nofollow noreferrer"><code>cvRunningAvg</code></a> function. It finds running average of frames from your video which you use to track. But you can obviously understand, first method is better, if you get background image.</p> <p><a href="http://sundararajana.blogspot.in/2007/05/motion-detection-using-opencv.html" rel="nofollow noreferrer">Here is the implementation</a> of above method using cvRunningAvg.</p> <p><strong>Case 2 - Camera not static</strong></p> <p>Here background subtraction won't give good result, since you can't get a fixed background.</p> <p>Then OpenCV come with a sample for people detection sample. Use it.</p> <p>This is the file: <a href="https://code.ros.org/trac/opencv/browser/trunk/opencv/samples/cpp/peopledetect.cpp" rel="nofollow noreferrer">peopledetect.cpp</a></p> <p>I also recommend you to visit this SOF which deals with almost same problem: <a href="https://stackoverflow.com/questions/2188646/how-can-i-detect-and-track-people-using-opencv">How can I detect and track people using OpenCV?</a></p>
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    1. POsingle person tracking from video sequence
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    1. USAbid Rahman K
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    1. COThanks a lot for your great advice :) For Case1: So the tracking here is just detection of the human frame-by-frame? How can I get the speed and movement direction of the detected person? I have read some articles and they commonly use Kalman filter (which I don't have knowledge) for tracking.
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    2. COWell, that is a larger topic. Please ask it as a seperate question about that with all the details. It is also discussed in SOF(stackoverflow) a lot of times. Better search for Kalman filter etc. in SOF before you ask the question.
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