3D object articulation and motion estimation in model-based stereoscopic videoconference image sequence analysis and coding

This paper describes a procedure for model-based analysis and coding of both left and right channels of a stereoscopic image sequence. The proposed scheme starts with a hierarchical dynamic programming technique for matching across the epipolar line for efficient disparity/depth estimation. Foreground/background segmentation is initially based on depth estimation and is improved using motion and luminance information. The model is initialised by the adaptation of a wireframe model to the consistent depth information. Robust classification techniques are then used to obtain an articulated description of the foreground of the scene (head, neck, shoulders). The object articulation procedure is based on a novel scheme for the segmentation of the rigid 3D motion fields of the triangle patches of the 3D model object. Spatial neighbourhood constraints are used to improve the reliability of the original triangle motion estimation. The motion estimation and motion field segmentation procedures are repeated iteratively until a satisfactory object articulation emerges. The rigid 3D motion is then re-computed for each sub-object and finally, a novel technique is used to estimate flexible motion of the nodes of the wireframe from the rigid 3D motion vectors computed for the wireframe triangles containing each specific node. The performance of the resulting analysis and compression method is evaluated experimentally. (C) 1999 Elsevier Science B.V. All rights reserved.