Design of optimized prefilters for time-domain lapped transforms with various downsampling factors

In image compression, decimation and interpolation techniques as pre-/postprocessing of a compression framework offer excellent energy compaction capability for low bit rate image coding. However, an interpolation filter cannot be defined as the inverse matrix of the given decimation filter since the former is a wide matrix and the latter is a tall one. Even without any compression, there will be some distortions in the reconstructed image. To tackle the problem, interpolation-dependent image downsampling (IDID) method produces optimized downsampled images, which leads to the optimized prefilter of a given postfilter. In this paper, we propose to integrate IDID with time-domain lapped transforms (TDLTs) to improve image coding performances.