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The tool presented in this paper performs an automatic segmentation of stereoscopic image sequences, based on the modeling of distance maps obtained by image processing. Two three-dimensional (3-D) image analysis algorithms are combined: i) estimation of dense depth maps from stereoscopic image sequences and ii) depth-based object segmentation. A Markovian statistical approach for such a segmentation of a dense depth map into arbitrarily shaped and oriented planar surfaces is described in detail. The simulation results on sequences 'Fun fair' and 'Tunnel,' provided on video tape to the MPEG-4 tests of November 1995, are discussed. Index Terms - Binocular disparity, depth-based segmentation, depth estimation, Markovian statistical approach, object-based segmentation.

This paper describes a region-based coding algorithm developed by Thomson Multimedia and submitted to MPEG-4 tests of November 1995 and January 1996. In this algorithm, the segmentation into regions is based on an advanced motion analysis, successively achieving a multiresolution motion field estimation and a segmentation based on a Markovian statistical approach, which insures a good temporal coherence of segmentation maps and an identification of covered areas. Moreover, the accurate motion description allows an intermediate frames interpolation which can increase the displayed frame rate. Simulation results and MPEG-4 tests of January 1996 have shown that the algorithm is as efficient as block-based coding algorithms like MPEG-1 or H.263 for the compression functionality, while offering temporal scalability by higher frame rates. Moreover, description of the scene in coherent motion regions may be seen as an intermediate step toward object-based functionalities. Index Terms - Motion analysis, motion segmentation, MPEG-4, multimedia, region-based coding techniques, video compression.