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audioconvert: use the same biquad as filter-chain
This commit is contained in:
Wim Taymans
parent
98365470c7
commit
0a0b1d594b
4 changed files with 338 additions and 68 deletions
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@ -8,9 +8,6 @@
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* found in the LICENSE.WEBKIT file.
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*/
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#include <spa/utils/defs.h>
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#include <math.h>
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#include "biquad.h"
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@ -18,9 +15,8 @@
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#define M_PI 3.14159265358979323846
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#endif
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#ifndef M_SQRT2
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#define M_SQRT2 1.41421356237309504880
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#endif
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/* S = 1 in Q */
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#define BIQUAD_SHELVING_DEFAULT_Q 0.707106781186548
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static void set_coefficient(struct biquad *bq, double b0, double b1, double b2,
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double a0, double a1, double a2)
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@ -33,82 +29,346 @@ static void set_coefficient(struct biquad *bq, double b0, double b1, double b2,
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bq->a2 = (float)(a2 * a0_inv);
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}
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static void biquad_lowpass(struct biquad *bq, double cutoff)
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static void biquad_lowpass(struct biquad *bq, double cutoff, double resonance)
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{
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/* Limit cutoff to 0 to 1. */
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cutoff = SPA_CLAMP(cutoff, 0.0, 1.0);
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cutoff = fmax(0.0, fmin(cutoff, 1.0));
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if (cutoff >= 1.0) {
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/* When cutoff is 1, the z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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} else if (cutoff > 0) {
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/* Compute biquad coefficients for lowpass filter */
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double theta = M_PI * cutoff;
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double sn = 0.5 * M_SQRT2 * sin(theta);
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double beta = 0.5 * (1 - sn) / (1 + sn);
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double gamma_coeff = (0.5 + beta) * cos(theta);
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double alpha = 0.25 * (0.5 + beta - gamma_coeff);
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double b0 = 2 * alpha;
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double b1 = 2 * 2 * alpha;
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double b2 = 2 * alpha;
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double a1 = 2 * -gamma_coeff;
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double a2 = 2 * beta;
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set_coefficient(bq, b0, b1, b2, 1, a1, a2);
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} else {
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/* When cutoff is zero, nothing gets through the filter, so set
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if (cutoff == 1 || cutoff == 0) {
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/* When cutoff is 1, the z-transform is 1.
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* When cutoff is zero, nothing gets through the filter, so set
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* coefficients up correctly.
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*/
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set_coefficient(bq, 0, 0, 0, 1, 0, 0);
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set_coefficient(bq, cutoff, 0, 0, 1, 0, 0);
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return;
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}
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/* Compute biquad coefficients for lowpass filter */
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resonance = fmax(0.0, resonance); /* can't go negative */
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double g = pow(10.0, 0.05 * resonance);
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double d = sqrt((4 - sqrt(16 - 16 / (g * g))) / 2);
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double theta = M_PI * cutoff;
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double sn = 0.5 * d * sin(theta);
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double beta = 0.5 * (1 - sn) / (1 + sn);
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double gamma = (0.5 + beta) * cos(theta);
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double alpha = 0.25 * (0.5 + beta - gamma);
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double b0 = 2 * alpha;
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double b1 = 2 * 2 * alpha;
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double b2 = 2 * alpha;
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double a1 = 2 * -gamma;
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double a2 = 2 * beta;
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set_coefficient(bq, b0, b1, b2, 1, a1, a2);
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}
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static void biquad_highpass(struct biquad *bq, double cutoff)
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static void biquad_highpass(struct biquad *bq, double cutoff, double resonance)
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{
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/* Limit cutoff to 0 to 1. */
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cutoff = SPA_CLAMP(cutoff, 0.0, 1.0);
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cutoff = fmax(0.0, fmin(cutoff, 1.0));
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if (cutoff >= 1.0) {
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/* The z-transform is 0. */
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set_coefficient(bq, 0, 0, 0, 1, 0, 0);
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} else if (cutoff > 0) {
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/* Compute biquad coefficients for highpass filter */
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double theta = M_PI * cutoff;
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double sn = 0.5 * M_SQRT2 * sin(theta);
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double beta = 0.5 * (1 - sn) / (1 + sn);
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double gamma_coeff = (0.5 + beta) * cos(theta);
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double alpha = 0.25 * (0.5 + beta + gamma_coeff);
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double b0 = 2 * alpha;
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double b1 = 2 * -2 * alpha;
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double b2 = 2 * alpha;
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double a1 = 2 * -gamma_coeff;
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double a2 = 2 * beta;
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set_coefficient(bq, b0, b1, b2, 1, a1, a2);
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} else {
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if (cutoff == 1 || cutoff == 0) {
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/* When cutoff is one, the z-transform is 0. */
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/* When cutoff is zero, we need to be careful because the above
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* gives a quadratic divided by the same quadratic, with poles
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* and zeros on the unit circle in the same place. When cutoff
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* is zero, the z-transform is 1.
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*/
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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set_coefficient(bq, 1 - cutoff, 0, 0, 1, 0, 0);
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return;
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}
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/* Compute biquad coefficients for highpass filter */
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resonance = fmax(0.0, resonance); /* can't go negative */
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double g = pow(10.0, 0.05 * resonance);
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double d = sqrt((4 - sqrt(16 - 16 / (g * g))) / 2);
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double theta = M_PI * cutoff;
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double sn = 0.5 * d * sin(theta);
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double beta = 0.5 * (1 - sn) / (1 + sn);
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double gamma = (0.5 + beta) * cos(theta);
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double alpha = 0.25 * (0.5 + beta + gamma);
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double b0 = 2 * alpha;
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double b1 = 2 * -2 * alpha;
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double b2 = 2 * alpha;
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double a1 = 2 * -gamma;
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double a2 = 2 * beta;
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set_coefficient(bq, b0, b1, b2, 1, a1, a2);
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}
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void biquad_set(struct biquad *bq, enum biquad_type type, double freq)
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static void biquad_bandpass(struct biquad *bq, double frequency, double Q)
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{
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/* No negative frequencies allowed. */
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frequency = fmax(0.0, frequency);
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/* Don't let Q go negative, which causes an unstable filter. */
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Q = fmax(0.0, Q);
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if (frequency <= 0 || frequency >= 1) {
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/* When the cutoff is zero, the z-transform approaches 0, if Q
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* > 0. When both Q and cutoff are zero, the z-transform is
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* pretty much undefined. What should we do in this case?
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* For now, just make the filter 0. When the cutoff is 1, the
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* z-transform also approaches 0.
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*/
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set_coefficient(bq, 0, 0, 0, 1, 0, 0);
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return;
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}
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if (Q <= 0) {
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/* When Q = 0, the above formulas have problems. If we
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* look at the z-transform, we can see that the limit
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* as Q->0 is 1, so set the filter that way.
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*/
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double b0 = alpha;
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double b1 = 0;
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double b2 = -alpha;
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double a0 = 1 + alpha;
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double a1 = -2 * k;
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double a2 = 1 - alpha;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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static void biquad_lowshelf(struct biquad *bq, double frequency, double Q,
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double db_gain)
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{
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/* Clip frequencies to between 0 and 1, inclusive. */
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frequency = fmax(0.0, fmin(frequency, 1.0));
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double A = pow(10.0, db_gain / 40);
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if (frequency == 1) {
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/* The z-transform is a constant gain. */
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set_coefficient(bq, A * A, 0, 0, 1, 0, 0);
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return;
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}
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if (frequency <= 0) {
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/* When frequency is 0, the z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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/* Set Q to an equivalent value to S = 1 if not specified */
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if (Q <= 0)
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Q = BIQUAD_SHELVING_DEFAULT_Q;
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double k2 = 2 * sqrt(A) * alpha;
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double a_plus_one = A + 1;
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double a_minus_one = A - 1;
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double b0 = A * (a_plus_one - a_minus_one * k + k2);
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double b1 = 2 * A * (a_minus_one - a_plus_one * k);
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double b2 = A * (a_plus_one - a_minus_one * k - k2);
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double a0 = a_plus_one + a_minus_one * k + k2;
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double a1 = -2 * (a_minus_one + a_plus_one * k);
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double a2 = a_plus_one + a_minus_one * k - k2;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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static void biquad_highshelf(struct biquad *bq, double frequency, double Q,
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double db_gain)
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{
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/* Clip frequencies to between 0 and 1, inclusive. */
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frequency = fmax(0.0, fmin(frequency, 1.0));
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double A = pow(10.0, db_gain / 40);
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if (frequency == 1) {
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/* The z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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if (frequency <= 0) {
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/* When frequency = 0, the filter is just a gain, A^2. */
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set_coefficient(bq, A * A, 0, 0, 1, 0, 0);
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return;
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}
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/* Set Q to an equivalent value to S = 1 if not specified */
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if (Q <= 0)
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Q = BIQUAD_SHELVING_DEFAULT_Q;
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double k2 = 2 * sqrt(A) * alpha;
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double a_plus_one = A + 1;
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double a_minus_one = A - 1;
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double b0 = A * (a_plus_one + a_minus_one * k + k2);
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double b1 = -2 * A * (a_minus_one + a_plus_one * k);
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double b2 = A * (a_plus_one + a_minus_one * k - k2);
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double a0 = a_plus_one - a_minus_one * k + k2;
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double a1 = 2 * (a_minus_one - a_plus_one * k);
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double a2 = a_plus_one - a_minus_one * k - k2;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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static void biquad_peaking(struct biquad *bq, double frequency, double Q,
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double db_gain)
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{
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/* Clip frequencies to between 0 and 1, inclusive. */
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frequency = fmax(0.0, fmin(frequency, 1.0));
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/* Don't let Q go negative, which causes an unstable filter. */
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Q = fmax(0.0, Q);
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double A = pow(10.0, db_gain / 40);
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if (frequency <= 0 || frequency >= 1) {
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/* When frequency is 0 or 1, the z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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if (Q <= 0) {
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/* When Q = 0, the above formulas have problems. If we
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* look at the z-transform, we can see that the limit
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* as Q->0 is A^2, so set the filter that way.
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*/
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set_coefficient(bq, A * A, 0, 0, 1, 0, 0);
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return;
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}
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double b0 = 1 + alpha * A;
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double b1 = -2 * k;
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double b2 = 1 - alpha * A;
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double a0 = 1 + alpha / A;
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double a1 = -2 * k;
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double a2 = 1 - alpha / A;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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static void biquad_notch(struct biquad *bq, double frequency, double Q)
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{
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/* Clip frequencies to between 0 and 1, inclusive. */
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frequency = fmax(0.0, fmin(frequency, 1.0));
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/* Don't let Q go negative, which causes an unstable filter. */
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Q = fmax(0.0, Q);
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if (frequency <= 0 || frequency >= 1) {
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/* When frequency is 0 or 1, the z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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if (Q <= 0) {
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/* When Q = 0, the above formulas have problems. If we
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* look at the z-transform, we can see that the limit
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* as Q->0 is 0, so set the filter that way.
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*/
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set_coefficient(bq, 0, 0, 0, 1, 0, 0);
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return;
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}
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double b0 = 1;
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double b1 = -2 * k;
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double b2 = 1;
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double a0 = 1 + alpha;
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double a1 = -2 * k;
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double a2 = 1 - alpha;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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static void biquad_allpass(struct biquad *bq, double frequency, double Q)
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{
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/* Clip frequencies to between 0 and 1, inclusive. */
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frequency = fmax(0.0, fmin(frequency, 1.0));
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/* Don't let Q go negative, which causes an unstable filter. */
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Q = fmax(0.0, Q);
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if (frequency <= 0 || frequency >= 1) {
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/* When frequency is 0 or 1, the z-transform is 1. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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return;
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}
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if (Q <= 0) {
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/* When Q = 0, the above formulas have problems. If we
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* look at the z-transform, we can see that the limit
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* as Q->0 is -1, so set the filter that way.
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*/
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set_coefficient(bq, -1, 0, 0, 1, 0, 0);
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return;
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}
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double w0 = M_PI * frequency;
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double alpha = sin(w0) / (2 * Q);
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double k = cos(w0);
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double b0 = 1 - alpha;
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double b1 = -2 * k;
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double b2 = 1 + alpha;
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double a0 = 1 + alpha;
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double a1 = -2 * k;
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double a2 = 1 - alpha;
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set_coefficient(bq, b0, b1, b2, a0, a1, a2);
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}
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void biquad_set(struct biquad *bq, enum biquad_type type, double freq, double Q,
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double gain)
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{
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/* Clear history values. */
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bq->type = type;
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bq->x1 = 0;
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bq->x2 = 0;
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switch (type) {
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case BQ_NONE:
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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break;
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case BQ_LOWPASS:
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biquad_lowpass(bq, freq);
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biquad_lowpass(bq, freq, Q);
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break;
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case BQ_HIGHPASS:
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biquad_highpass(bq, freq);
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biquad_highpass(bq, freq, Q);
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break;
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case BQ_BANDPASS:
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biquad_bandpass(bq, freq, Q);
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break;
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case BQ_LOWSHELF:
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biquad_lowshelf(bq, freq, Q, gain);
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break;
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case BQ_HIGHSHELF:
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biquad_highshelf(bq, freq, Q, gain);
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break;
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case BQ_PEAKING:
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biquad_peaking(bq, freq, Q, gain);
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break;
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case BQ_NOTCH:
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biquad_notch(bq, freq, Q);
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break;
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case BQ_ALLPASS:
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biquad_allpass(bq, freq, Q);
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break;
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case BQ_NONE:
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case BQ_RAW:
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/* Default is an identity filter. */
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set_coefficient(bq, 1, 0, 0, 1, 0, 0);
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break;
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}
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}
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@ -10,6 +10,20 @@
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extern "C" {
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#endif
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/* The type of the biquad filters */
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enum biquad_type {
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BQ_NONE,
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BQ_LOWPASS,
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BQ_HIGHPASS,
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BQ_BANDPASS,
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BQ_LOWSHELF,
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BQ_HIGHSHELF,
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BQ_PEAKING,
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BQ_NOTCH,
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BQ_ALLPASS,
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BQ_RAW,
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};
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/* The biquad filter parameters. The transfer function H(z) is (b0 + b1 * z^(-1)
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* + b2 * z^(-2)) / (1 + a1 * z^(-1) + a2 * z^(-2)). The previous two inputs
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* are stored in x1 and x2, and the previous two outputs are stored in y1 and
|
||||
|
|
@ -19,15 +33,10 @@ extern "C" {
|
|||
* float is used during the actual filtering for faster computation.
|
||||
*/
|
||||
struct biquad {
|
||||
enum biquad_type type;
|
||||
float b0, b1, b2;
|
||||
float a1, a2;
|
||||
};
|
||||
|
||||
/* The type of the biquad filters */
|
||||
enum biquad_type {
|
||||
BQ_NONE,
|
||||
BQ_LOWPASS,
|
||||
BQ_HIGHPASS,
|
||||
float x1, x2;
|
||||
};
|
||||
|
||||
/* Initialize a biquad filter parameters from its type and parameters.
|
||||
|
|
@ -36,8 +45,11 @@ enum biquad_type {
|
|||
* type - The type of the biquad filter.
|
||||
* frequency - The value should be in the range [0, 1]. It is relative to
|
||||
* half of the sampling rate.
|
||||
* Q - Quality factor. See Web Audio API for details.
|
||||
* gain - The value is in dB. See Web Audio API for details.
|
||||
*/
|
||||
void biquad_set(struct biquad *bq, enum biquad_type type, double freq);
|
||||
void biquad_set(struct biquad *bq, enum biquad_type type, double freq, double Q,
|
||||
double gain);
|
||||
|
||||
#ifdef __cplusplus
|
||||
} /* extern "C" */
|
||||
|
|
|
|||
|
|
@ -10,7 +10,7 @@
|
|||
|
||||
void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq)
|
||||
{
|
||||
biquad_set(&lr4->bq, type, freq);
|
||||
biquad_set(&lr4->bq, type, freq, 0, 0);
|
||||
lr4->x1 = 0;
|
||||
lr4->x2 = 0;
|
||||
lr4->y1 = 0;
|
||||
|
|
|
|||
|
|
@ -25,6 +25,4 @@ struct lr4 {
|
|||
|
||||
void lr4_set(struct lr4 *lr4, enum biquad_type type, float freq);
|
||||
|
||||
void lr4_process(struct lr4 *lr4, float *dst, const float *src, const float vol, int samples);
|
||||
|
||||
#endif /* CROSSOVER_H_ */
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue