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Contents
module SPCore
# Implement a "cookbook" highpass filter using the BiquadFilter class,
# based on the well-known RBJ biquad filter.
class CookbookHighpassFilter < BiquadFilter
def initialize sample_rate
super(sample_rate)
end
def set_critical_freq_and_bw critical_freq, bandwidth
@critical_freq = critical_freq
@bandwidth = bandwidth
# setup variables
omega = 2.0 * Math::PI * @critical_freq / @sample_rate
sn = Math::sin(omega)
cs = Math::cos(omega)
alpha = sn * Math::sinh(BiquadFilter::LN_2 / 2.0 * @bandwidth * omega / sn)
b0 = (1.0 + cs) / 2.0
b1 =-(1.0 + cs)
b2 = (1.0 + cs) / 2.0
a0 = 1.0 + alpha
a1 = -2.0 * cs
a2 = 1.0 - alpha
# precompute the coefficients
@biquad.b0 = b0 / a0
@biquad.b1 = b1 / a0
@biquad.b2 = b2 / a0
@biquad.a0 = a0 / a0
@biquad.a1 = a1 / a0
@biquad.a2 = a2 / a0
## zero initial samples
#@biquad.x1 = @biquad.x2 = 0
#@biquad.y1 = @biquad.y2 = 0
end
end
end
Version data entries
9 entries across 9 versions & 1 rubygems