Low delay modulated filter bank

Abstract

The document relates to modulated sub-sampled digital filter banks, as well as to methods and systems for the design of such filter banks. In particular, the present document proposes a method and apparatus for the improvement of low delay modulated digital filter banks. The method employs modulation of an asymmetric low-pass prototype filter and a new method for optimizing the coefficients of this filter. Further, a specific design for a (64) channel filter bank using a prototype filter length of (640) coefficients and a system delay of (319) samples is given. The method substantially reduces artifacts due to aliasing emerging from independent modifications of subband signals, for example when using a filter bank as a spectral equalizer. The method is preferably implemented in software, running on a standard PC or a digital signal processor (DSP), but can also be hardcoded on a custom chip. The method offers improvements for various types of digital equalizers, adaptive filters, multiband companders and spectral envelope adjusting filterbanks used in high frequency reconstruction (HFR) or parametric stereo systems.

Description

technical field [0001] This document relates to modulated subsampling digital filter banks and methods and systems for designing such filter banks. Specifically, it provides a new design method and apparatus for near-ideally constructed low-delay cosine- or complex-exponential modulated filterbanks optimized to suppress the occurrence of aliasing. Also given is a specific design for a 64-channel filter bank using a prototype filter length of 640 coefficients and a system delay of 319 samples. Background technique [0002] The teachings herein can be applied as, for example, in "An Efficient 20 Band Digital Audio Equalizer" by A.J.S. Ferreira, J.M.N. Viera (AES Preprint, 98 th Digital filters as outlined in Convention 1995 February 25-28 Paris, N.Y., USA); as e.g. in A. Gilloire, M. Vetterli, "Adaptive Filtering in Subbands with Critical Sampling: Analysis, Experiments, and Application to Acoustic Echo Cancellation" (IEEE Transactions on Signal Processing, vol.40, no.8, A...

AI Technical Summary

Problems solved by technology

The use of short prototype filters usually results in relatively poor band separation properties and large frequency overlap regions between adjacent subbands

Thus, short prototype filters generally do not allow a filter bank design that adequately suppresses aliasing when modifying subband samples, requiring alternative designs of low-latency filter banks

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