The dyadic wavelet-based set partitioning in hierarchical trees (SPIHT) is highly efficient in coding nontextured images while the wavelet packet transform (WPT) is able to provide an optimal representation for textured images. However, incorporating the WPT with SPIHT to improve the performance of SPIHT is not as straightforward as it would seem. Although previous solutions generally adapt the zero-tree structure to the WPT, we introduce a method for selecting an optimal WPT basis for SPIHT, which efficiently compacts the high-frequency subband energy into as few trees as possible and avoids parental conflicts. The proposed SPIHT-WPT coder achieves improved coding gains, especially for highly textured images. Furthermore, the selected WPT is compatible with the region-of-interest and error resilient SPIHT coding schemes.
This paper presents a post-processing error concealment technique for handling transmission of DWT image coefficients. Our technique recovers the lost regularity information as well as irregularity information. First, the Harmonic Function is employed for overall smoothness recovery. Next, in order to enhance local edges, the spatial coherence between DWT subbands is explored. The amplitudes of those detected singular points are then modified, according to the regions they belong to. Our proposed method reveals edges from blurred areas due to smooth recovery accurately.