Optimal subband rate allocation for spatial scalability in 3D wavelet video coding with motion aligned temporal filtering

The shift-variant property of discrete wavelet transform leads to the intrinsic coupling across various spatial subbands during motion aligned temporal filtering. It brings a big challenge how to achieve a better trade-off between subband independency and motion alignment efficiency in the context of providing spatial scalability in 3D wavelet video coding. This paper first investigates the issue of subband coupling in-depth. From the investigations on analysis and synthesis filters, we verify the existence and causes of subband coupling phenomenon and illustrate the subband leakage due to motion shift. Furthermore, we propose a method to measure the strength of this kind of coupling. Based on these investigations, we focus on schemes which preserving most subband coupling relationship and recommend that spatial highpass subbands should not be dropped completely. The issue of rate allocation for spatial highpass subbands is considered in this paper. An error propagation model is proposed to describe the effect of subband coupling in video reconstruction. The synthesis gain of each subband is estimated according to this model and it is finally adopted to guide the rate allocation algorithm. Experimental results have fully demonstrated the promising of the proposed techniques in improving both objective and subjective qualities of low resolution video, especially at middle and high bit rates, for 3D video coding schemes with spatial scalability.