DCT-based general structure for linear-phase paraunitary filterbanks

In this paper, we present a general structure for linear phase paraunitary filterbanks (LPPUFB) via both time-domain pre-processing and frequency-domain post-processing of the discrete cosine transform (DCT). The proposed structure not only covers existing frameworks with either pre-processing or post-processing of the DCT but enables the design of DCT-based LPPUFB with both partial-block overlapping and variable-length filters as well. Some high-performance and low-complexity transforms can be obtained by fine-tuning the structure parameters. Furthermore, a DCT-oriented initialization method is developed to improve the convergence and to simplify the parameterization in the filterbank optimization process. The application in image compression is demonstrated.