Most mobile video applications require the encoder to have low complexity. Wyner-Ziv (WZ) video coding removes complex motion estimation from the encoder, and provides error resilience from the embedded channel coding module. WZ video coding is regarded as a promising encoder for wireless video systems. Most WZ video coding based on channel codes is a practical implementation of the binning schemes. In this work, we present a novel two-tier binning scheme that consists of the inner and outer structure, for improving rate-distortion performance. First, we develop a Raptor coding with side information to construct the inner binning structure, which provides a lower rate. Second, for the outer binning, we model the WZ video coding architecture as a multiaccess channel, so that we can exploit the property of channel capacity. Third, we exploit the duality property of WZ video coding. Based on such a property, both the primal and dual solutions are subsequently provided in this study. For the primal problem of distortion minimization, we develop dynamic programming to find the optimal binning policy, whereas for the dual problem of capacity maximization, we devise a near sum-capacity binning algorithm. The objective is to lower the coding rate with lower complexity. Experimental results showed that when compared with the state-of-the-art coding, the decoding performance and the quality of our proposed method were respectively enhanced. Besides, we observed that the decoding distortion was reduced through the proposed outer binning, while the proposed inner binning based on Raptor coding by jointly considering side information (SI) lead to a low bitrate when a target decoding quality was specified. Such findings have substantiated the effectiveness of our method.