Virtual character within MPEG-4 animation framework eXtension

Enriched multimedia applications and services aim at combining images, sounds, videos, and synthetic objects into hybrid and interactive scenes. The core technologies discussed here deal with the representation and integration within such complex scenes of a specific kind of synthetic data, namely virtual character animation. This paper analyzes how an integrated and standardized framework is currently emerging in order to ensure application interoperability, universal content access, and user interactivity. We first compare how virtual character animation has been addressed within virtual reality modeling language (VRML) and MPEG-4 synthetic and natural hybrid coding standardization processes. A comparative synthesis between the objectives and the capabilities of each framework is exposed, specifically MPEG-4 Face and Body Animation (FBA) versus H-Anim (Humanoid Animation Working Group, WEB3D Consortium, h-anim.org.) 1.1, and MPEG-4 Bone-Based Animation (BBA) versus H-Anim 2001. The Animation Framework eXtension (AFX) specifications that are a part of MPEG-4 Systems Part 16 include the BBA framework. The BBA animation concepts, based on generic skeleton representation and curve-based deformations, are introduced. The definition of the related nodes and how they successfully address the BBA concepts are as well discussed. Some comments with respect to the rotation representation, the interpolation methods, the animation mask, and value parameters of the animation stream are made. This set of specifications provides an efficient framework, which is appropriate to real-time and animation realistic applications within networked environments.