Multiband Filterbank

Audio filterbank for real-time audio signal processing implemented in C++. You can choose:

• Number of frequency bands
• Filter order
• Stopband attenuation

The project also contains a basic Up-/Downsampler. See Resampling.hpp

Details

Implements a filterbank that is allpass complementary meaning that it has a flat frequency response with some unnoticable phase distortion.

Filterbank Structure: R. Cassidy and J. O. Smith, "A tunable, nonsubsampled, non-uniform filter bank for multi-band audition and level modification of audio signals," Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers, 2004., 2004, pp. 2228-2232 Vol.2, doi: https://doi.org/10.1109/ACSSC.2004.1399563

Each filterbank stage uses a crossover filter based on IIR filters of type EMQF (Elliptic with minimal Q-factor).

EMQF Filter Design: Miroslav D. Lutovac, "Filter Design for Signal Processing Using MATLAB and Mathematica", 2000, Prentice Hall, ISBN-13: 978-0201361308

Integration

• Simple to use header-only C++ library. Just include the corresponding files from the afx directory.
• Note that it requires BOOST library for some special mathematical functions. bcp tool may be used for the following files:
  • boost/math/special_functions/jacobi_elliptic.hpp
  • boost/math/special_functions/ellint_1.hpp

TODO

• Implement better filter structure that is more suitable for time-varying operation. (Vadim Zavalishin's TPT)
• Prevent denormal numbers driving up CPU load when filter states are decayed.