The famous http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt offers a set of [real] biquad filter calculation formulas that generally work fine.
However, when filter's frequency approaches Nyquist frequency the Q (bandwidth) specification of a filter becomes greatly distorted - usually it shrinks a lot (even though the author mentioned that he performed a necessary pre-warping).
I'm in quest for filter formulas that do not have such strong bandwidth distortion. I need peaking/bell, band-pass, low-pass, high-pass, high-shelf, notch filters. I know this can be done as previously I've bought a peaking/bell/band-pass filter formulas with less distortion, but they are still not perfect and I need other filter types.
So, I'm also willing to pay for the solution if the price is right.
Alternatively, if one could point me to an optimization algorithm that works with Z-domain filters that would be great, too. Unfortunately, most usual optimization algorithms do not work well in Z-domain - they can't optimize a set of parameters to match a desired frequency response (probably due to periodic functions used to calculate the frequency response).
No comments:
Post a Comment