Drawbacks of Classical Filterbank Designs 2.4 2002/10/30 2005/09/30 15:41:31.712 GMT-5 Phil Schniter schniter@ee.eng.ohio-state.edu Michael Haag mjhaag@rice.edu Phil Schniter schniter@ee.eng.ohio-state.edu classical filterbanks filter banks filterbanks polyphase implementation Modules provides a very brief description of the drawbacks to the classical filterbank designs and introduces the need for more modern approaches. To begin with, the reference to "classical" filterbank designs, generally refers to the filterbank types that you should have seen up to now. These include the following types, that can be reviewed if necessary: Uniform Modulated Filterbanks Polyphase/DFT Implementation of Uniform Modulated Filterbanks

Drawbacks to Classical Implementation The classical filterbanks that we have considered so far (those listed above) give perfect reconstruction performance only when the analysis and synthesis filters are ideal. With non-ideal (i.e., implementable) filters, aliasing will result from the downsampling/upsampling operation and corrupt the output signal. Since aliasing distortion is inherently non-linear, it may be very undesirable in certain applications. Thus, long analysis/synthesis filters might be required to force aliasing distortion down to tolerable levels. The cost of long filters is somewhat offset by the efficient polyphase implementation, though. That said, clever fliter designs have been proposed which prevent aliasing in neighboring sub-bands. These designs include the following references: Rothweiler, Crochiere and Rabiner, and Vaidyanathan. As neighboring-subband aliasing typically constitutes the bulk of aliasing distortion, these designs give significant performance gains. In fact, such filter designs are used in MPEG high-performance audio compression standards.

J.H. Rothweiler Polyphase quadrature filters - A new subband coding technique 1983 R.E Crochiere and L.R. Rabiner Multirate Digital Signal Processing 1983 P.P. Vaidyanathan Multirate Systems and Filter Banks 1993