orastron/brickworks
2
1
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases 10 Wiki Activity

bw_src, fix coeffs, seriously

Browse Source
This commit is contained in:
Stefano D'Angelo 2023-04-04 15:23:05 +02:00
parent 5eed8c2878
commit 388ece962a
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/bw_src.h
View File

@ -121,7 +121,7 @@ static inline void bw_src_init(bw_src_coeffs *BW_RESTRICT coeffs, float ratio) {
coeffs->k = ratio >= 1.f ? 1.f / ratio : -1.f / ratio;
// 4th-degree Butterworth with cutoff at ratio * Nyquist, using bilinear transform w/ prewarping
const float fc = bw_minf((float)(ratio >= 1.f ? 1.f / ratio : ratio), 0.9f);
const float T = bw_tanf_3(1.570796326794896f / (float)fc);
const float T = bw_tanf_3(1.570796326794896f * (float)fc);
const float T2 = T * T;
const float k = 1.f / (T * (T * (T * (T + 2.613125929752753f) + 3.414213562373095f) + 2.613125929752753f) + 1.f);
coeffs->b0 = k * T2 * T2;
@ -201,9 +201,9 @@ static inline void bw_src_process(const bw_src_coeffs *BW_RESTRICT coeffs, bw_sr
const float v1 = coeffs->b1 * o;
const float v2 = coeffs->b2 * o;
y[j] = v0 + state->z1;
state->z1 = v1 * o - coeffs->a1 * y[j] + state->z2;
state->z1 = v1 - coeffs->a1 * y[j] + state->z2;
state->z2 = coeffs->b2 * o - coeffs->a2 * y[j] + state->z3;
state->z3 = v1 * o - coeffs->a3 * y[j] + state->z4;
state->z3 = v1 - coeffs->a3 * y[j] + state->z4;
state->z4 = v0 - coeffs->a4 * y[j];
state->i += coeffs->k;
j++;