<title>Image subband coding with adaptive filter banks</title>

Abstract

A fundamental problem with both FIR and IIR based image subband coders operating at low bit rates is the trade-off between ringing noise and blocking artifacts. The important parameter in this respect is the impulse response length of the filter bank channels. A short impulse response length is suitable for modeling image areas with a high degree of detail, but suffers from blocking effects. On the other hand, a long impulse response does not exhibit blocking effects, but will lead to ringing noise in the vicinity of edges. In this paper we show that IIR filter banks based on all pass filter building blocks can be made spatially adaptive without compromising their perfect reconstruction property. This rather surprising property is used to simultaneously minimize ringing artifacts and blocking effects in a subband coder.