rewrite filter calculations using plane conversion
this changes everything
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c4cfb2582d
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2 changed files with 43 additions and 91 deletions
107
crap_util.c
107
crap_util.c
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@ -15,100 +15,43 @@ biquad_init(biquad *bq) {
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}
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biquad_interim
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peaking(double cw, double Gf, double g) {
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double GB = sqrt(Gf);
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design(double cw, double sw,
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double num0, double num1, double num2,
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double den0, double den1, double den2) {
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return (biquad_interim) {
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.b0 = 1 + g * GB,
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.b1 = -2 * cw,
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.b2 = 1 - g * GB,
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.a0 = 1 + g / GB,
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.a1 = -2 * cw,
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.a2 = 1 - g / GB
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};
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}
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biquad_interim
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highpass(double cw, double g) {
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return (biquad_interim) {
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.b0 = (1 + cw)*0.5,
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.b1 = -cw - 1,
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.b2 = (1 + cw)*0.5,
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.a0 = 1 + g,
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.a1 = -2*cw,
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.a2 = 1 - g
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};
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}
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/* TODO: rename */
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biquad_interim
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orfanidi(double w0, double Gf, double g) {
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/* simplified http://ece.rutgers.edu/~orfanidi/intro2sp/mdir/peq.m */
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double Dw, GfS, F, G00, F00, term1, term2, num, den;
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double G1S, G1, G01, G11, F01, F11, W2, DO, coeff, C, D, A, B;
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double v;
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Dw = atan(g)*2;
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GfS = SQR(Gf);
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v = (Gf > 1) ? 1 : -1;
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F = v*(GfS - Gf);
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G00 = v*(GfS - 1);
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F00 = v*(Gf - 1);
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term1 = SQR(SQR(w0) - SQR(M_PI));
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term2 = F00 * SQR(M_PI) * SQR(Dw) / F;
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num = term1 + term2 * GfS;
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den = term1 + term2;
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G1S = num/den;
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G1 = sqrt(G1S);
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G01 = v*(GfS - G1);
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G11 = v*(GfS - G1S);
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F01 = v*(Gf - G1);
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F11 = fabs(Gf - G1S);
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/* bandwidth compensation goes nuts
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* skip |= v*(Gf - G1S) < 0; */
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W2 = sqrt(G11 / G00) * SQR(tan(w0/2));
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DO = (1 + sqrt(F00 / F11) * W2) * g;
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coeff = 2 * W2 / F;
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C = F11 * SQR(DO) / F - coeff * (F01 - sqrt(F00 * F11));
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D = coeff * (G01 - sqrt(G00 * G11));
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A = sqrt( C + D);
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B = sqrt(GfS * C + Gf * D);
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return (biquad_interim) {
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.b0 = -(G1 + W2 + B),
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.b1 = 2*(G1 - W2),
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.b2 = -(G1 - B + W2),
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.a0 = -(1 + W2 + A),
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.a1 = 2*(1 - W2),
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.a2 = -(1 + W2 - A)
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.b0 = num0* (1 + cw) + num1*sw + num2* (1 - cw),
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.b1 = num0*-2*(1 + cw) + num2*2*(1 - cw),
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.b2 = num0* (1 + cw) - num1*sw + num2* (1 - cw),
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.a0 = den0* (1 + cw) + den1*sw + den2* (1 - cw),
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.a1 = den0*-2*(1 + cw) + den2*2*(1 - cw),
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.a2 = den0* (1 + cw) - den1*sw + den2* (1 - cw),
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};
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}
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biquad
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biquad_gen(int type, double fc, double gain, double bw, double fs) {
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/* TODO: use enum for type instead of just int */
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double w0, cw, sw, Gf, Q, a_peak, a_pass;
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double w0, cw, sw, A, As, Q;
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w0 = ANGULAR_LIM(fc, fs);
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cw = cos(w0);
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sw = sin(w0);
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Gf = DB2LIN(gain);
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Q = 1/(2 * sinh(LN_2_2 * bw * w0/sw));
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A = DB2LIN(gain/2);
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As = sqrt(A);
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Q = 1/(4 * sinh(LN_2_2 * bw * w0/sw));
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//Q = bw? - (w0/M_PI)^2;
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/* skip = (fabs(A - 1) <= TINY); */
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a_peak = sw * (2 / Q);
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a_pass = sw / (1 * Q);
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/* skip = (fabs(Gf - 1) <= TINY); */
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biquad_interim bqi;
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if (type == 0) bqi = peaking(cw, Gf, a_peak);
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if (type == 1) bqi = orfanidi(w0, Gf, a_peak);
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if (type == 2) bqi = highpass(cw, a_pass);
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if (type == 0) bqi = design(cw,sw, 1, A/Q, 1, 1, 1/A/Q, 1);
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if (type == 1) bqi = design(cw,sw, 1, As/Q, A, 1, 1/As/Q, 1/A);
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if (type == 2) bqi = design(cw,sw, A, As/Q, 1, 1/A, 1/As/Q, 1);
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if (type == 3) bqi = design(cw,sw, 0, 0, 1, 1, 1/Q, 1);
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if (type == 4) bqi = design(cw,sw, 1, 0, 0, 1, 1/Q, 1);
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if (type == 5) bqi = design(cw,sw, 1, -1/Q, 1, 1, 1/Q, 1);
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if (type == 6) bqi = design(cw,sw, 0, 1, 0, 1, 1/Q, 1);
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if (type == 7) bqi = design(cw,sw, 0, 1/Q, 0, 1, 1/Q, 1);
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if (type == 8) bqi = design(cw,sw, 1, 0, 1, 1, 1/Q, 1);
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if (type == 9) bqi = design(cw,sw, A, A, A, 1/A, 1/A, 1/A);
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double a0r = 1/bqi.a0;
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27
crap_util.h
27
crap_util.h
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@ -44,18 +44,27 @@ typedef struct {
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void
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biquad_init(biquad *bq);
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biquad_interim
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peaking(double cw, double Gf, double g);
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biquad_interim
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highpass(double cw, double g);
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biquad_interim
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orfanidi(double w0, double Gf, double g);
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/* types: TODO: enum
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0: peaking
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1: lowshelf
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2: highshelf
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3: lowpass
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4: highpass
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5: allpass
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6: bandpass 1
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7: bandpass 2
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8: notch
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9: gain
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*/
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biquad
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biquad_gen(int type, double fc, double gain, double bw, double fs);
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/* s-plane to z-plane */
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biquad_interim
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design(double cw, double sw,
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double num0, double num1, double num2,
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double den0, double den1, double den2);
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bq_t
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biquad_run(biquad *bq, bq_t x);
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