Efficient compression and delivery of stored motion data for avatar animation in resource constrained devices

ABSTRACT

Animation of Virtual Humans (avatars) is done typically using motion data files that are stored on a client or streaming motion data from a server. Several modern applications require avatar animation in mobile networked virtual environments comprising of power constrained clients such as PDAs, Pocket-PCs and notebook PCs operating in battery mode. These applications call for efficient compression of the motion animation data in order to conserve network bandwidth, and save power at the client side during data reception and motion data reconstruction from the compressed file. In this paper, we have proposed and implemented a novel file format, termed the Quantized Motion Data (QMD) format, which enables significant, though lossy, compression of the motion data. The motion distortion resulting from the reconstructed motion from the QMD file is minimized by intelligent use of the hierarchical structure of the skeletal avatar model. The compression gained by using the QMD files for the motion data is more than twice achieved via standard MPEG-4 compression using a pipeline comprising of quantization, predictive encoding and arithmetic coding. In addition, considerably fewer CPU cycles are needed to reconstruct the motion data from the QMD files compared to motion data compressed using the MPEG-4 standard.

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INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism
          Subjects: Animation

General Terms:
Algorithms, Performance

Keywords:
avatar animation, distributed virtual reality, human motion