Design of Optimized Prefilters for Time-Domain Lapped Transforms with Various Downsampling Factors

Masaki ONUKI

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E97-A    No.9    pp.1907-1917
Publication Date: 2014/09/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E97.A.1907
Type of Manuscript: PAPER
Category: Digital Signal Processing
biorthogonal filterbank,  lapped transform,  image coding,  downsampling,  interpolation,  

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Decimation and interpolation methods are utilized in image coding for low bit rate image coding. However, the decimation filter (prefilter) and the interpolation filter (postfilter) are irreversible with each other since the prefilter is a wide matrix (a matrix whose number of columns are larger than that of rows) and the postfilter is a tall one (a matrix whose number of rows are larger than that of columns). There will be some distortions in the reconstructed image even without any compression. The method of interpolation-dependent image downsampling (IDID) was used to tackle the problem of producing optimized downsampling images, which led to the optimized prefilter of a given postfilter. We propose integrating the IDID with time-domain lapped transforms (TDLTs) to improve image coding performance.