From bc529ea9bc0c6ee9ed8301a62b26e60e686a2db0 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Wed, 25 Nov 2020 22:23:50 +0100
Subject: [PATCH] avfilter/af_acrossover: use transposed direct II form
---
libavfilter/af_acrossover.c | 32 +++++++++++++-------------------
1 file changed, 13 insertions(+), 19 deletions(-)
diff --git a/libavfilter/af_acrossover.c b/libavfilter/af_acrossover.c
index bd84223681..f8c4d1f25a 100644
--- a/libavfilter/af_acrossover.c
+++ b/libavfilter/af_acrossover.c
@@ -41,8 +41,7 @@
typedef struct BiquadContext {
double a0, a1, a2;
double b1, b2;
- double i1, i2;
- double o1, o2;
+ double z1, z2;
} BiquadContext;
typedef struct CrossoverChannel {
@@ -150,8 +149,8 @@ static void set_lp(BiquadContext *b, double fc, double q, double sr)
b->a0 = (0.5 + beta - gamma) / 2.0;
b->a1 = 0.5 + beta - gamma;
b->a2 = b->a1 / 2.0;
- b->b1 = -2.0 * gamma;
- b->b2 = 2.0 * beta;
+ b->b1 = 2.0 * gamma;
+ b->b2 = -2.0 * beta;
}
static void set_hp(BiquadContext *b, double fc, double q, double sr)
@@ -164,8 +163,8 @@ static void set_hp(BiquadContext *b, double fc, double q, double sr)
b->a0 = (0.5 + beta + gamma) / 2.0;
b->a1 = -(0.5 + beta + gamma);
b->a2 = b->a0;
- b->b1 = -2.0 * gamma;
- b->b2 = 2.0 * beta;
+ b->b1 = 2.0 * gamma;
+ b->b2 = -2.0 * beta;
}
static void calc_q_factors(int order, double *q)
@@ -246,26 +245,21 @@ static void biquad_process(BiquadContext *b,
const double a2 = b->a2;
const double b1 = b->b1;
const double b2 = b->b2;
- double i1 = b->i1;
- double i2 = b->i2;
- double o1 = b->o1;
- double o2 = b->o2;
+ double z1 = b->z1;
+ double z2 = b->z2;
for (int n = 0; n < nb_samples; n++) {
const double in = src[n];
double out;
- out = in * a0 + i1 * a1 + i2 * a2 - o1 * b1 - o2 * b2;
- i2 = i1;
- o2 = o1;
- i1 = in;
- o1 = dst[n] = out;
+ out = in * a0 + z1;
+ z1 = a1 * in + z2 + b1 * out;
+ z2 = a2 * in + b2 * out;
+ dst[n] = out;
}
- b->i1 = i1;
- b->i2 = i2;
- b->o1 = o1;
- b->o2 = o2;
+ b->z1 = z1;
+ b->z2 = z2;
}
static int filter_channels(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)