Rate-distortion modeling for binary shape in MPEG-4

In this paper, we explore the rate-distortion (R-D) characteristics of binary shape information in the MPEG-4 standard. The shape coding scheme is a block based context-based arithmetic (CAE) encoding approach and distortion is introduced by down- and up-sampling. Generally, the shape bit rate and non-normalized distortion increase in proportion with the number of border blocks. The more complex object suffers from more distortion under the same resolution scale. Consequently, we propose a rate-distortion model based on the parameters derived from the border blocks and a block-based shape complexity (SC) for the video object. The computational complexity is much lower than other existing methods. Experimental results show that it can accurately predict the bit rate and distortion of the binary shape for rate control purpose.