A new class of optimal biorthogonal subband coder

In this letter, we introduce a novel two-channel biorthogonal subband coder . The new coder employs the ladder structure (or so-called wavelet with lif ting scheme). The coding gain of the biorthogonal coder is always greater t han or equal to unity, and it can be expressed in closed form. Moreover the proposed coder has a very low complexity and the perfect reconstruction pr operty is structurally preserved. Given any filter order, the optimal solut ion can be found by the well-known Levinson fast algorithm. For both AR(1) process and MA(1) process, the proposed biorthogonal coder with 2 taps has a higher coding than the optimal orthonormal coder with infinite number of taps.