a-EQ: Transfer function curves improvement

diff --git a/libs/plugins/a-eq.lv2/a-eq.c b/libs/plugins/a-eq.lv2/a-eq.c
index c0b7259ed581fb62dda60c249f7186dbac81bb55..6ee42ed270b57457646a78084d26ff6d8578ac44 100644 (file)
--- a/libs/plugins/a-eq.lv2/a-eq.c
+++ b/libs/plugins/a-eq.lv2/a-eq.c
@@ -453,9 +453,13 @@ eq_curve (Aeq* self, float f) {
        double complex H = 1.0;
        double theta = f * 2. * M_PI / SR;
        double complex z = cexp(I * theta);
+       double complex zz = cexp(2 * I * theta);
+       double complex zm = z - 1.0;
+       double complex zp = z + 1.0;
+       double complex zzm = zz - 1.0;
+
        double A;
        double m0, m1, m2, g, k;
-       int j = 0;
 
        // low
        if (self->v_filtog[0]) {
@@ -467,60 +471,47 @@ eq_curve (Aeq* self, float f) {
                k = self->v_filter[0].k;
                if (self->v_shelftogl) {
                        // lowshelf
-                       H *= (A*m0*(z-1.0)*(z-1.0) + g*g*(m0+m2)*(1.0+z)*(1.0+z) + sqrt(A)*g*(k*m0+m1) * (z*z-1.0)) / (A*(z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z) + sqrt(A)*g*k*(z*z-1.0));
+                       H *= (A*m0*zm*zm + g*g*(m0+m2)*zp*zp + sqrt(A)*g*(k*m0+m1) * zzm) / (A*zm*zm + g*g*zp*zp + sqrt(A)*g*k*zzm);
                } else {
                        // hp:
-                       H *= ((z-1.0)*(z-1.0)) / ((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z) + g*k*(z*z-1.0));
+                       H *= zm*zm / (zm*zm + g*g*zp*zp + g*k*zzm);
                }
-               j++;
        }
 
        // peq1:
        if (self->v_filtog[1]) {
                A = pow(10.0, self->v_g[1]/40.0);
-               m0 = self->v_filter[1].m[0];
-               m1 = self->v_filter[1].m[1];
-               m2 = self->v_filter[1].m[2];
+               m1 = self->v_filter[1].m[1] / A;
                g = self->v_filter[1].g;
                k = self->v_filter[1].k;
-               H *= (g*k*m0*(z*z-1.0) + A*(g*(1.0+z)*(m1*(z-1.0) + g*m2*(1.0+z)) + m0*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)))) / (g*k*(z*z-1.0) + A*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)));
-               j++;
+               H *= (g*k*zzm + A*(g*zp*(m1*zm + g*m2*zp) + (zm*zm + g*g*zp*zp))) / (g*k*zzm + A*(zm*zm + g*g*zp*zp));
        }
 
        // peq2:
        if (self->v_filtog[2]) {
                A = pow(10.0, self->v_g[2]/40.0);
-               m0 = self->v_filter[2].m[0];
-               m1 = self->v_filter[2].m[1];
-               m2 = self->v_filter[2].m[2];
+               m1 = self->v_filter[2].m[1] / A;
                g = self->v_filter[2].g;
                k = self->v_filter[2].k;
-               H *= (g*k*m0*(z*z-1.0) + A*(g*(1.0+z)*(m1*(z-1.0) + g*m2*(1.0+z)) + m0*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)))) / (g*k*(z*z-1.0) + A*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)));
-               j++;
+               H *= (g*k*zzm + A*(g*zp*(m1*zm + g*m2*zp) + (zm*zm + g*g*zp*zp))) / (g*k*zzm + A*(zm*zm + g*g*zp*zp));
        }
 
        // peq3:
        if (self->v_filtog[3]) {
                A = pow(10.0, self->v_g[3]/40.0);
-               m0 = self->v_filter[3].m[0];
-               m1 = self->v_filter[3].m[1];
-               m2 = self->v_filter[3].m[2];
+               m1 = self->v_filter[3].m[1] / A;
                g = self->v_filter[3].g;
                k = self->v_filter[3].k;
-               H *= (g*k*m0*(z*z-1.0) + A*(g*(1.0+z)*(m1*(z-1.0) + g*m2*(1.0+z)) + m0*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)))) / (g*k*(z*z-1.0) + A*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)));
-               j++;
+               H *= (g*k*zzm + A*(g*zp*(m1*zm + g*m2*zp) + (zm*zm + g*g*zp*zp))) / (g*k*zzm + A*(zm*zm + g*g*zp*zp));
        }
 
        // peq4:
        if (self->v_filtog[4]) {
                A = pow(10.0, self->v_g[4]/40.0);
-               m0 = self->v_filter[4].m[0];
-               m1 = self->v_filter[4].m[1];
-               m2 = self->v_filter[4].m[2];
+               m1 = self->v_filter[4].m[1] / A;
                g = self->v_filter[4].g;
                k = self->v_filter[4].k;
-               H *= (g*k*m0*(z*z-1.0) + A*(g*(1.0+z)*(m1*(z-1.0) + g*m2*(1.0+z)) + m0*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)))) / (g*k*(z*z-1.0) + A*((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z)));
-               j++;
+               H *= (g*k*zzm + A*(g*zp*(m1*zm + g*m2*zp) + (zm*zm + g*g*zp*zp))) / (g*k*zzm + A*(zm*zm + g*g*zp*zp));
        }
 
        // high
@@ -533,12 +524,11 @@ eq_curve (Aeq* self, float f) {
                k = self->v_filter[5].k;
                if (self->v_shelftogh) {
                        // highshelf:
-                       H *= ( sqrt(A) * g * (1.0 + z) * (m1 * (z - 1.0) + sqrt(A)*g*m2*(1.0+z)) + m0 * ( (z-1.0)*(z-1.0) + A*g*g*(1.0+z)*(1.0+z) + sqrt(A)*g*k*(z*z-1.0))) / ((z-1.0)*(z-1.0) + A*g*g*(1.0+z)*(1.0+z) + sqrt(A)*g*k*(z*z-1.0));
+                       H *= ( sqrt(A) * g * zp * (m1 * zm + sqrt(A)*g*m2*zp) + m0 * ( zm*zm + A*g*g*zp*zp + sqrt(A)*g*k*zzm)) / (zm*zm + A*g*g*zp*zp + sqrt(A)*g*k*zzm);
                } else {
                        // lp:
-                       H *= (g*g*(1.0+z)*(1.0+z)) / ((z-1.0)*(z-1.0) + g*g*(1.0+z)*(1.0+z) + g*k*(z*z-1.0));
+                       H *= (g*g*zp*zp) / (zm*zm + g*g*zp*zp + g*k*zzm);
                }
-               j++;
        }
 
        return cabs(H);