1. MPEG Video Technology Virtual Lab Tour: Vision Systems for Mobile Robots By: Soradech Krootjohn Vanderbilt University Center for Intelligent Systems Feb. 15, 2006

2. What is MPEG? MPEG (Moving Picture Experts Group) Used for coding audio-visual information in a digital compressed format MP3 is the audio-only portion of MPEG and is commonly used for music.

3. Where can we find MPEG video? MPEG-1 –Video CD, Video clips on Internet MPEG-2 –DVD –Digital Cable TV & Satellite TV MPEG-4 –Supports a wide range of applications: Wireless/mobile multimedia such as videos on cell-phone or video clips on internet (higher quality than MPEG-1) Video production in studios

4. Digital Video Signal Digital video signal is composed of a series of still images, representing a natural visual scene.

5. 12345678910 Video Clip Sample Frame:

6. How MPEG Works? Encode only changes occurring between video frames by predicting motion occuring between frames Each video frame may be encoded as: I Frame: –Simply encode current frame as it appears (No prediction) P Frame: –Current frame is predicted based on the previous frame B Frame: –Current frame is predicted based on the previous and future frames

7. P-Frame Prediction Current P FramePrevious I or P Frame

8. B-Frame Prediction Bi-Directional Predicted Frame Current B Frame Previous I or P FrameFuture I or P Frame Both Previous and Future I or P Frames

9. Macroblocks Divide current frame into Macroblocks (16x16 pixels) Previous Frame ( Reference Frame ) Current Frame ( Predicted Frame )

10. Motion Vectors Current frame is divided into Macroblocks The Motion Vector describes the direction and distance the current Macroblock moved from the previous frame to the current frame We use these Motion Vectors to enable the robot to detect motion.