Idealized Data for Motion Detection 1.3 2005/12/07 22:08:03 US/Central 2005/12/23 13:16:57.650 US/Central Grant S Lee grantlee@rice.edu Siddharth Gupta sgupta@rice.edu Veena Padmanabhan veena@rice.edu Heather E Johnston heatherj@rice.edu Grant S Lee grantlee@rice.edu Siddharth Gupta sgupta@rice.edu Veena Padmanabhan veena@rice.edu Heather E Johnston heatherj@rice.edu Richard G. Baraniuk richb@rice.edu data selection Details on what kinds of data are used to test our system, and how they were selected. The main purpose of our device is to detect velocity of motions in a movie file, and it is helpful to understand the mechanism in idealized cases. It is too complicated to come up with appropriate algorithms for all possible input data at once, and we want to look at the simpliest cases first. Our choice of data is a simulated movie. Reducing to bare bones, a blank, constant background(noise-free) with a single object moving across the screen is a good start.

Making Frames Manual coding of movies was done in MATLAB, using matrices of zeros and ones. zeros represents background, and ones represent an object. For simplicity, movies are in grayscale (black for zeros and white for ones).

Matrix To Frame Command 'imagesc(matrix)' on MATLAB will give us a simple picture

Looking at above matrix, different shapes can easily be made by arranging the ones in different layouts. We have created square, vertical rectangle, horizontal rectangle, triangle, and circle shapes. Once a desired image with an object is created, the 'getframe' command in MATLAB converts images to frames.

Making Movies To make a movie of a "moving" object (represented as a group of ones), our program can simply create multiple frames with the group of ones in different locations. One can move most any object in any direction in a reasonable frame size. However, creating a movie with non-axial motion can be very tedious in MATLAB, so we chose motions along the horizontal and vertical axis. For our purpose, we set the screen size to be 256x256. Each pixel corresponds to one entry in the matrix.

Moving Square Square moving into the screen

Square in the screen

Different velocities can be achieved by varying number of pixels moved over per frame. In other words, within the same number of frames, a movie with a faster object will have its object moved over further across the screen than one with a slower object.

Moving Triangle With Different Speeds Triangle moving at 10 pixels per frame

Triangle moving at 50 pixels per frame