LINC. A common theory of transform and subband coding

Abstract

A common theory of lapped orthogonal transforms (LOT's) and critically sampled filter banks, called 'L into N coding' (LINC), is presented. The theory includes a unified analysis of both coding methods and identify relations between transform, inverse transform, analysis filter bank, and synthesis filter bank. A design procedure for LINC-analysis/synthesis systems, which satisfy the conditions for perfect reconstruction, is developed. The common LINC-theory is used to define an ideal LINC system, with which theoretical bounds for the coding gain are calculated using the power spectral density of the input signal. A generalized overlapping block transform (OBT) with time domain aliasing cancellation (TDAC) is used to approximate the ideal LINC. The generalization of the OBT includes multiple block overlap and additional windowing. A recursive design procedure for windows of arbitrary lengths is presented. The coding gain of the generalized OBT is higher than that of the KLT and close to the theoretical bounds of LINC. In the case of image coding, the generalized OBT reduces the blocking effects when compared to the DCT.