A new approach to recursive mirror filters with a special application in subband coding of images

A novel method for applying recursive mirror filters (RMF) in applications where infinite delay can be tolerated is presented. This type of situation can be found in several circumstances, but the method has its main applications in a technique of subband coding of images which was presented by J.W. Woods and S.D. O´Neill (ibid., vol.ASSP-34, p.1278-88, Oct. 1986). In image coding, a delay is only a shift in a spatial coordinate. The present method has looser filter constraints than previous recursive quadrature mirror filter (QMF) techniques, but may in certain applications require a large memory. Contrary to earlier recursive-QMF techniques, this approach leads to a linear phase characteristic, a property that is vital in image coding