1. A method of video surveillance comprising: receiving input video comprising a plurality of input video frames; performing on the plurality of input video frames at least one of motion detection or change detection to obtain at least one foreground mask having a plurality of foreground pixels and a time stamp; generating at least one motion block within an area of interest of the input video based on the obtained at least one foreground mask; analyzing the generated at least one motion block to detect periodic motion of an object within the area of interest; and generating at least one alert if periodic motion is detected, wherein said generating at least one motion block comprises: dividing one of the at least one foreground mask having a plurality of foreground pixels and one time stamp to obtain at least one block having a search window; determining a number of foreground pixels present in the search window of the obtained at least one block; comparing the number of foreground pixels present in the search window of the obtained at least one block with a threshold value; and generating at least one motion block having the time stamp of the foreground mask from which said at least one block is obtained, if the threshold value has been surpassed, wherein said analyzing the generated at least one motion block further comprises: determining a period of time for which the generated at least one motion block has had its number of foreground pixels exceed said threshold value; comparing said period of time with a time threshold; if the period of time is larger than said time threshold, storing the pixel coordinates and time stamp of the generated at least one motion block in a motion block array for further analysis; obtaining the pixel coordinates and time stamp of one motion block within the area of interest from the motion block array; comparing the obtained time stamp to the time stamp(s) of at least one other motion block in the motion block array to determine if the differences between the obtained time stamp and the time stamp(s) of at least one other motion block are larger than a difference threshold; defining a periodic motion counter for each set of pixel coordinates; and incrementing the periodic motion counter for the obtained pixel coordinates corresponding to the same motion block as that of the obtained time stamp if the differences between the obtained time stamp and the time stamp(s) of at least one other motion block are larger than the difference threshold.