Symmetric Extension of Signals for Subband Coding

S.-W. Park (USA)


Subband coding, wavelet transform, periodic extension, symmetric extension, filtering.


Coefficient expansion is a problem in subband coding when a signal is filtered. One simple way to eliminate coefficient expansion is to use periodic extension before filtering. However, periodic extension introduces discontinuity at both edges that makes highpass filter output coefficients larger than they should be. To prevent it, symmetric extension is used along with symmetric or anti-symmetric filters. This tutorial paper presents some examples of symmetric extension for subband coding that includes biorthogonal wavelet transform and QMF.

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