diff options
Diffstat (limited to 'src/common/filter.c')
| -rw-r--r-- | src/common/filter.c | 37 |
1 files changed, 27 insertions, 10 deletions
diff --git a/src/common/filter.c b/src/common/filter.c index f568f1b..3aea327 100644 --- a/src/common/filter.c +++ b/src/common/filter.c @@ -26,14 +26,18 @@ #define PI M_PI -//#define CASCADE - -void filter_lowpass_init(filter_lowpass_t *bq, double frequency, int samplerate) +void filter_lowpass_init(filter_t *bq, double frequency, int samplerate, int iterations) { double Fc, Q, K, norm; + if (iterations > 64) { + fprintf(stderr, "%s failed: too many iterations, please fix!\n", __func__); + abort(); + } + memset(bq, 0, sizeof(*bq)); - Q = sqrt(0.5); /* 0.7071... */ + bq->iter = iterations; + Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */ Fc = frequency / (double)samplerate; K = tan(PI * Fc); norm = 1 / (1 + K / Q + K * K); @@ -44,18 +48,31 @@ void filter_lowpass_init(filter_lowpass_t *bq, double frequency, int samplerate) bq->b2 = (1 - K / Q + K * K) * norm; } -void filter_lowpass_process(filter_lowpass_t *bq, double *samples, int length, int iterations) +void filter_highpass_init(filter_t *bq, double frequency, int samplerate, int iterations) +{ + double Fc, Q, K, norm; + + memset(bq, 0, sizeof(*bq)); + bq->iter = iterations; + Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */ + Fc = frequency / (double)samplerate; + K = tan(PI * Fc); + norm = 1 / (1 + K / Q + K * K); + bq->a0 = 1 * norm; + bq->a1 = -2 * bq->a0; + bq->a2 = bq->a0; + bq->b1 = 2 * (K * K - 1) * norm; + bq->b2 = (1 - K / Q + K * K) * norm; +} + +void filter_process(filter_t *bq, double *samples, int length) { double a0, a1, a2, b1, b2; double *z1, *z2; double in, out; + int iterations = bq->iter; int i, j; - if (iterations > 10) { - fprintf(stderr, "%s failed: too many iterations, please fix!\n", __func__); - abort(); - } - /* get states */ a0 = bq->a0; a1 = bq->a1; |