Sprite Coding in Object-based Video Coding Standard: MPEG-4

This paper outlines a new standard video compression technology: MPEG-4. We propose a very efficient coding scheme using the one of compression tools of MPEG-4 “Sprite coding”. We first introduce MPEG-4 visual “Profiles”, which are sets of tools (technical elements) that realize certain types of applications. Among these “Profiles”, “Main Profile” is capable of using “Sprites” i.e. a unified background image derived from a sequence having camera motion. We propose a new technique to split foreground moving objects from the background “Sprite” automatically for more efficient video compression than is possible with conventional technologies. We call the algorithm the “Two-layer video object plane (VOP) generation scheme”. The two-layer VOP generation scheme has several core algorithms such as global motion estimation, foreground moving object extraction, and background sprite generation. The foreground object is MPEG-4 object coded in the main profile, while the background sprite is coded using MPEG-4 sprite coding. We call this coding scheme “sprite mode”; MPEG-4 simple profile coding is called “normal mode”. Experiments are conducted on VOP generation and video coding with MPEG-4. We compare sprite mode to normal mode. The coding efficiency of sprite mode is several times higher than that of normal mode at the same objective image quality if the foreground ratio is within 10-15%.