Real-Time Video Object Segmentation for MPEG Encoded Video Sequences

We propose a real-time object segmentation method for MPEG encoded video. Computational superiority is the main advantage of compressed domain processing. We exploit the macro-block structure of the encoded video to decrease the spatial resolution of the processed data, which exponentially reduces the computational load. Further reduction is achieved by temporal grouping of the intra-coded and estimated frames into a single feature layer. In addition to computational advantage, compressed-domain video possesses important features attractive for object analysis. Texture characteristics are provided by the DCT coefficients. Motion information is readily available without incurring cost of estimating a motion field. To achieve segmentation, the DCT coefficients for I-frames and block motion vectors for P-frames are combined and a frequencytemporal data structure is constructed. Starting from the blocks where the ac-coefficient energy and local inter-block dc-coefficient variance is small, the homogeneous volumes are enlarged by evaluating the distance of candidate vectors to the volume characteristics. Affine motion models are fit to volumes. Finally, a hierarchical clustering stage iteratively merges the most similar parts to generate an object partition tree as an output. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c ©Mitsubishi Electric Research Laboratories, Inc., 2004 201 Broadway, Cambridge, Massachusetts 02139