; general order-2 IIR filter. ; a0 is assumed to be unity. ; for a1 and a2, our sign convention is opposite to Matlab's. (EQBANDVVV-ALG (NAME "eqbandvvv") (ARGUMENTS ("sound_type" "input") ("sound_type" "hz") ("sound_type" "gain") ("sound_type" "width") ) (SUPPORT-FUNCTIONS "#define log_of_2_over_2 0.3465735902799726547086\n") (START (MIN input hz gain width)) (TERMINATE (MIN input hz gain width)) (LOGICAL-STOP (MIN input hz gain width)) (SAMPLE-RATE (MAX input)) ;;(INTERNAL-SCALING input hz gain width) (INLINE-INTERPOLATION T) (MATCHED-SAMPLE-RATE hz gain width) (ALWAYS-SCALE input hz gain width) (STEP-FUNCTION hz gain width) (STATE ("double" "inp_scale" "input->scale") ("double" "w1" "0.0") ("double" "sw" "0.0") ("double" "cw" "0.0") ("double" "J" "0.0") ("double" "gg" "0.0") ("double" "b0" "0.0") ("double" "b1" "0.0") ("double" "b2" "0.0") ("double" "a0" "0.0") ("double" "a1" "0.0") ("double" "a2" "0.0") ("double" "z1" "0.0") ("double" "z2" "0.0") ("boolean" "recompute" "false") ("double" "inp_period" "1.0 / input->sr")) (DEPENDS ("w1" "hz" "PI2 * hz * inp_period") ("sw" "hz" "sin(w1)") ("cw" "hz" "cos(w1)") ("b1" "hz" "-2.0 * cw") ("a1" "hz" "-b1") ("J" "gain" "sqrt(gain)") ("recompute" "width" "true") ("recompute" "hz" "true") ("recompute" "gain" "true") ) (JOINT-DEPENDENCY (("width" "hz") "if (recompute) {" " /* a0 = 1.0 + gg / J; */" " double a_0_recip = J / (J + gg);" " recompute = false;" " gg = sw * sinh(log_of_2_over_2 * width * w1 / sw);" " b0 = (1.0 + gg * J) * a_0_recip;" " b1 *= a_0_recip;" " b2 = (1.0 - gg * J) * a_0_recip;" " a1 *= a_0_recip;" " a2 = (gg / J - 1.0) * a_0_recip;" "}")) (FORCE-INTO-REGISTER recompute inp_period cw) (CONSTANT "w1" "sw" "cw" "J" "gg" "b0" "b1" "b2" "b3" "a0" "a1" "a2" "inp_period") (INNER-LOOP-LOCALS " double z0;\n") (INNER-LOOP " z0 = input + a1*z1 + a2*z2; output = (sample_type) (z0*b0 + z1*b1 + z2*b2); z2 = z1; z1 = z0;") )