Over-sampled and under-sampled pre-post-filters for block DCT coders

Pre-post-filtering operators have been shown to improve the coding efficiency as well as to mitigate blocking artifacts in traditional DCT-based block coders. Pre-post-filters which preserve the system sampling rate have been extensively investigated. This paper explores the two noncritically-sampled signal decomposition cases - under-sampling and over-sampling - via the pre-post-processing perspective. We discuss various design issues, efficient structures, and present two application examples: under-sampled pre-post-filters for very low bit-rate image coding and over-sampled pre-post-filters for error resilient image transmission. Preliminary experimental results illustrate that noncritically-sampled pre-post-filtering does provide much improved coding performances than its critically-sampled counterpart for the aforementioned specific applications.