title: Which computer vision library & algorithm(s), for human behaviour analysis?
body: <p><strong>Objective:</strong> Detect / determine human actions, s.a. picking / lifting items to read label and keeping it back on rack (in a store), sitting-on, mounting/climbing-atom objects s.a. chair, bench, ladder etc.</p>
  
  <p><strong>Environment:</strong> Store / shop, which is mostly well lit. Cameras (VGA -> 1MP), fixed (i.e. not PTZ).</p>
  
  <p><strong>Constraints:</strong> </p>
  
  <ol>
  <li>Presence of known and unknown human beings. </li>
  <li>Possible rearrangement of objects (items for sale) in the store, over a period of time.</li>
  <li>Possible changes in lighting over time. 
  For example: Frontal areas of store might get ample sunlight during day, which changes to artificial light at night. Also, during night more lights can be switched-on.</li>
  </ol>
  
  <p><strong>Question:</strong></p>
  
  <ol>
  <li><p>While I understand that OpenCV is great for face-detection and usable for face-recognition, can it be used for analyzing "actions", s.a. the act of sitting, the act of lifting an object off the shelf ? If so, what are some of these algorithms I should dig deeper into ?</p></li>
  <li><p>Since cameras in stores are mostly at ceiling height, they generally do not have a frontal face view, but mostly a top-down view. I understand that Haar Cascade (PCA) isn't quite usable, but one needs other methods s.a. 3D Head geometry determination. Are there other libraries (other than OpenCV) which need to be used for such tasks ? Are there open-source libraries for the same ?</p></li>
  </ol>