Theoretical Model of the Coding Error in MCWT Video Coders

In motion-compensated wavelet based video coders (MCWT), it is known that a precise motion estimation is necessary to minimize the wavelet coefficients energy. However, a motion vectors field of high precision is expensive in binary resources compared to the wavelet subbands. In order to reduce the quantity of bits required to represent these vectors, we proposed in a previous work to quantize the motion vectors using a scalable and open-loop lossy coder, while controlling the rate-distortion trade-off. Obviously, this lossy motion coding has an impact on the decoded sequence. In this paper, we propose to evaluate this impact by establishing a theoretical distortion model of motion coding error, including also the subbands quantization noise. This model will allow to realize an optimal model-based bit-rate allocation between wavelet coefficients and motion information. Experimental validation of the model gives interesting results.