Context-adaptive binary arithmetic coding for frame-based animated mesh compression

Context-based adaptive binary arithmetic coding (CABAC) has proven to be an efficient technique in the area of video coding. This paper presents an approach for integrating CABAC into the framework of frame-based animated mesh compression (FAMC). It presents the specific modifications and adaptations that have been worked out to adapt CABAC to the specific requirements of FAMC in order to build a solution with a higher degree of coding efficiency. For a typical test set of animated meshes, average bit rate savings of 25% have been observed for the combination of CABAC and FAMC when compared to a previous version of FAMC using a conventional N-ary arithmetic coder. The presented approach has been recently adopted as part of the MPEG-4 AFX standard.

1. INTRODUCTION

From dynamic 3D scenes recorded by multiple cameras a scene representation with 3D video objects (3DVOs) can be reconstructed, using synthetic geometry and real video texture sequences from the original cameras [1]. The synthetic geometry of such 3DVOs is often approximated by planar 3D meshes for every time instance. The single 3D meshes are further transformed into time-consistent animated mesh sequences. The mesh sequences consist of an initial intra or I mesh as well as a number of predictively coded or P meshes. The I mesh contains the initial 3D vertex positions as well as the connectivity to define the mesh faces. Each P mesh only contains the new vertex positions and uses the connectivity from the I-mesh.