Adaptive wavelet filter design for optimized image source encoding
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Despite intensive research being conducted on the topic of adaptive filter design in general, adaptive filter design in the discrete wavelet transform (DWT) domain with specific constraints is still an active research area. The present work investigates the advantages and limitations of the design of a 2-chanel perfect-reconstruction wavelet filter which is adapted and optimized under minimum energy constraints in a specific band. Such a filter can be used with a quantizer and entropy encoder of a wavelet based image encoder to give optimum performance. An optimal 2-channel conjugate quadrature filter (CQF) bank has been designed and optimized using Sequential Quadratic Programming methods. The filter bank problem is solved using recently developed optimization techniques for general nonlinear, non-convex functions. The results indicate an improved performance for this method compared to the earlier-used Interior-Point optimization method.