Generalized discrete multiwavelet transform with embedded prefilter bank for VQ-based image coding

Prefiltering is required to initialize the scalar signal for the discrete multiwavelet transform (DMWT). Traditional prefilters are not linear phase, often nonorthogonal or nonmaximally decimated. Recently, we suggested an orthogonal symmetric prefilter bank (OSPFB) to tackle this problem but it was still difficult to find a compatible filter bank structure and sometimes there was none, especially for low multiplicity multiwavelets. A new generalized DMWT structure was then proposed by combining the prefilters with the first stage of DMWT. It has the advantages of lower computational complexity and more freedom on designing the prefilters. In this paper, the performance of the new DMWT structure is evaluated by applying to a VQ-based image coding system whose codebook is initialized with a modified approach called cumulative absolute difference (CAD). Satisfactory results are obtained in all cases comparing with the traditional approaches.