Modeling the Motion Coding Error for Mcwt Video Coders

In motion-compensated wavelet based video coders, a very precise motion estimation is necessary. However, a motion vectors field of high precision is expensive in binary resources and requires a great place in the bitstream compared to the wavelet coefficients. Thus, we need to reduce the cost of the motion information. To this end, we propose an approach based on a scalable lossy coding of high-precision motion vectors. It allows to optimize the trade-off between motion bit-rate and wavelet coefficients bit-rate, strongly reduces the motion cost, and thus, increases the coder performances at low bit-rate. Obviously, this lossy motion coding has an impact on the decoded sequence. In this paper, we evaluate this impact by establishing a theoretical distortion model for the motion coding error. This model allows the realization of an optimal model-based bit-rate allocation between wavelet subbands and motion vectors. The experimental validation of the model gives satisfactory results