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avfilter/af_aiir: improve response calculation with zp coefficients

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This commit is contained in:
Paul B Mahol 2020-05-30 09:47:12 +02:00
parent e2e8121eaa
commit 3fc7b01c52
1 changed files with 23 additions and 31 deletions
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54
libavfilter/af_aiir.c
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@ -824,9 +824,14 @@ static void draw_line(AVFrame *out, int x0, int y0, int x1, int y1, uint32_t col
}
}
static double distance(double x0, double x1, double y0, double y1)
{
return hypot(x0 - x1, y0 - y1);
}
static void get_response(int channel, int format, double w,
const double *b, const double *a,
int nb_b, int nb_a, double *r, double *i)
int nb_b, int nb_a, double *magnitude, double *phase)
{
double realz, realp;
double imagz, imagp;
@ -849,39 +854,26 @@ static void get_response(int channel, int format, double w,
div = realp * realp + imagp * imagp;
real = (realz * realp + imagz * imagp) / div;
imag = (imagz * realp - imagp * realz) / div;
*magnitude = hypot(real, imag);
*phase = atan2(imag, real);
} else {
real = 1;
imag = 0;
double p = 1., z = 1.;
double acc = 0.;
for (int x = 0; x < nb_a; x++) {
double ore, oim, re, im;
re = cos(w) - a[2 * x];
im = sin(w) - a[2 * x + 1];
ore = real;
oim = imag;
real = ore * re - oim * im;
imag = ore * im + oim * re;
z *= distance(cos(w), a[2 * x], sin(w), a[2 * x + 1]);
acc += atan2(sin(w) - a[2 * x + 1], cos(w) - a[2 * x]);
}
for (int x = 0; x < nb_b; x++) {
double ore, oim, re, im;
re = cos(w) - b[2 * x];
im = sin(w) - b[2 * x + 1];
ore = real;
oim = imag;
div = re * re + im * im;
real = (ore * re + oim * im) / div;
imag = (oim * re - ore * im) / div;
p *= distance(cos(w), b[2 * x], sin(w), b[2 * x + 1]);
acc -= atan2(sin(w) - b[2 * x + 1], cos(w) - b[2 * x]);
}
}
*r = real;
*i = imag;
*magnitude = z / p;
*phase = acc;
}
}
static void draw_response(AVFilterContext *ctx, AVFrame *out, int sample_rate)
@ -909,12 +901,12 @@ static void draw_response(AVFilterContext *ctx, AVFrame *out, int sample_rate)
const int nb_b = s->iir[ch].nb_ab[0];
const int nb_a = s->iir[ch].nb_ab[1];
double w = i * M_PI / (s->w - 1);
double real, imag;
double m, p;
get_response(ch, s->format, w, b, a, nb_b, nb_a, &real, &imag);
get_response(ch, s->format, w, b, a, nb_b, nb_a, &m, &p);
mag[i] = s->iir[ch].g * hypot(real, imag);
phase[i] = atan2(imag, real);
mag[i] = s->iir[ch].g * m;
phase[i] = p;
min = fmin(min, mag[i]);
max = fmax(max, mag[i]);
}