class AudioStream::Fx::BandPassFilter

Public Class Methods

create(soundinfo, freq:, bandwidth: 1.0) click to toggle source

@param soundinfo [AudioStream::SoundInfo] @param freq [Float] Center frequency @param bandwidth [Float] bandwidth (octave)

# File lib/audio_stream/fx/band_pass_filter.rb, line 25
def self.create(soundinfo, freq:, bandwidth: 1.0)
  filter = new(soundinfo)
  filter.update_coef(freq: freq, bandwidth: bandwidth)

  filter
end

Public Instance Methods

update_coef(freq:, bandwidth:) click to toggle source
# File lib/audio_stream/fx/band_pass_filter.rb, line 5
def update_coef(freq:, bandwidth:)
  omega = 2.0 * Math::PI * freq / @samplerate
  alpha = Math.sin(omega) * Math.sinh(Math.log(2.0) / 2.0 * bandwidth * omega / Math.sin(omega))

  a0 = 1.0 + alpha
  a1 = -2.0 * Math.cos(omega)
  a2 = 1.0 - alpha
  b0 = alpha
  b1 = 0.0
  b2 = -alpha

  @coef = Vdsp::Biquad::Coefficient.new(b0/a0, b1/a0, b2/a0, a1/a0, a2/a0)
  @biquads.each {|biquad|
    biquad.coefficients = @coef
  }
end