filter-duby.rb

  def apply(input0:float[], output0:float[], sampleFrames:int)
    output0[0] = @a1 * input0[0] + @a2 * @ih1_1 + @a3 * @ih1_2 - @b1*@oh1_1 - @b2*@oh1_2
    output0[1] = @a1 * input0[1] + @a2 * input0[0] + @a3 * @ih1_1 - @b1*output0[0] - @b2*@oh1_1

    sample = 2
    while sample < sampleFrames
      output0[sample] = @a1*input0[sample] + @a2*input0[sample-1] + @a3*input0[sample-2] - @b1*output0[sample-1] - @b2*output0[sample-2]
      sample += 1
    end

    @ih1_1 = input0[sampleFrames-1]
    @ih1_2 = input0[sampleFrames-2]
    @oh1_1 = output0[sampleFrames-1]
    @oh1_2 = output0[sampleFrames-2]
  end