Mahn-Jin Han

Interpolator data compression for MPEG-4 animation

Interpolator representation in key-frame animation is now the most popular method for computer animation. The interpolator data consist of key and key value pairs, where a key is a time stamp and a key value is the corresponding value to the key. In this paper, we propose a set of new technologies to compress the interpolator data. The performance of the proposed technique is compared with the existing MPEG-4 generic compression tool. Throughout the core experiments in MPEG-4, the proposed technique showed its superiority over the existing tool, becoming a part of MPEG-4 standard within the Animation Framework eXtension framework.

Depth image-based representation and compression for static and animated 3-D objects

This paper describes a new family of three-dimensional (3-D) representations for computer graphics and animation, called depth image-based representations (DIBR), which have been adopted into MPEG-4 Part16: Animation Framework eXtension (AFX). Idea of the approach is to build a compact and photorealistic representation of a 3-D object or scene without using polygonal mesh. Instead, images accompanied by depth values for each pixel are used. This type of representation allows us to build and render novel views of objects and scene with an interactive rate. There are many different methods for the image-based rendering with depths, and the DIBR format is designed to efficiently represent the information necessary for such methods. The main formats of the DIBR family are SimpleTexture (an image together with depth array), PointTexture (an image with multiple pixels along each line of sight), and OctreeImage (octree-like data structure together with a set of images containing viewport parameters). In order to store and transmit the DIBR object, we develop a compression algorithm and bitstream format for OctreeImage representation.

Depth image-based representations for static and animated 3D objects

We describe a novel depth image-based representation (DIBR) that has been adopted into the MPEG-4 animation framework extension (AFX). The idea of this approach is to build a compact representation of a 3D object or scene without storing the geometry information in traditional polygonal form. The main formats of the DIBR family are simple texture (an image together with depth array), point texture (a view of a scene from a single input camera but with multiple pixels along each line of sight), and octree image (octree data structure together with a set of images and their viewport parameters). The designed node specifications and rendering algorithms are addressed. The experimental results show the efficacy and fidelity of the proposed approach.

Animation data compression in MPEG-4: interpolators

In this paper, we propose new technologies to compress the interpolator nodes in VRML/MPEG-4 BIFS (binary format for scene). Interpolators are used to animate the 3D objects in a VRML/MPEG-4 BIFS scene. For interactive applications with quite a few animated 3D synthetic objects, two components are dominant in the amount of data to represent the animation: 3D object and its animation. In the current MPEG-4, 3D model coding (3DMC) yields a high compression ratio with reasonable quality for the 3D object, while predictive MFField coding (PMFC) yields a moderate compression ratio with reasonable quality for the animation data. The proposed techniques are to provide a high compression on animation data and have been adopted to MPEG-4 system amendment 4 (AFX/MUW).