LINC - A COMMON THEORY OF TRANSFORM AND SUBBAND CODING

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 id entity 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 reconstru ction, is developed. The common LINC-theory is used to define an ideal LINC system, with which theoretical bounds for the coding gain are ca lculated using the power spectral density of the input signal. A gener alized overlapping block transform (OBT) with time domain aliasing can cellation (TDAC) is used to approximate the ideal LINC. The generaliza tion of the OBT includes multiple block overlap and additional windowi ng. A recursive design procedure for windows of arbitrary lengths is p resented. The coding gain of the generalized OBT is higher than that o f the KLT and close to the theoretical bounds of LINC. In the case of image coding, the generalized OBT reduces the blocking effects when co mpared to the DCT.