A rate-distortion optimal coding alternative to matching pursuit
This paper presents a method to find the operational rate-distortion optimal solution for an overcomplete signal decomposition. The idea of using overcomplete dictionaries, or frames, is to get a sparse representation of the signal. Traditionally, suboptimal algorithms, such as Matching Pursuit (MP), is used for this purpose. When using frames in a lossy compression scheme, the major issue is to find the best possible rate-distortion (RD) tradeoff. Given the frame and the Variable Length Code (VLC) table embedded in the entropy coder, the solution of the problem of establishing the best RD tradeoff has a very high complexity. The proposed approach reduces this complexity significantly by structuring the solution approach such that the dependent quantizer allocation problem reduces into an independent one. It is important to note that this large reduction in complexity is achieved without sacrificing optimality. The optimal rate-distortion solution depends on the VLC table embedded in the entropy coder. Thus, VLC optimization is part of this work. We show experimentally that the new approach outperforms Rate-Distortion Optimized Matching Pursuit, previously proposed in [1].