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resample: use cosh window function

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Seem to produce a little sharper cutoff.

Fixes #2483
This commit is contained in:
Wim Taymans 2022-06-29 18:03:40 +02:00
parent 9b37142ef6
commit a44c600ade
1 changed files with 12 additions and 3 deletions
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15
spa/plugins/audioconvert/resample-native.c
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@ -58,14 +58,23 @@ static inline double sinc(double x)
return sin(x) / x; return sin(x) / x;
} }
static inline double blackman(double x, double n_taps) #if 0
static inline double window_blackman(double x, double n_taps)
{ {
double alpha = 0.232; double alpha = 0.232;
x = 2.0 * M_PI * x / n_taps; x = 2.0 * M_PI * x / n_taps;
return (1.0 - alpha) / 2.0 + (1.0 / 2.0) * cos(x) + return (1.0 - alpha) / 2.0 + (1.0 / 2.0) * cos(x) +
(alpha / 2.0) * cos(2 * x); (alpha / 2.0) * cos(2 * x);
} }
#else
static inline double window_cosh(double x, double n_taps)
{
double R = 95.0;
double A = -325.1E-6 * (R * R) + 0.1677 * R - 3.149;
x = 2.0 * M_PI * x / n_taps;
return cosh(A * sqrt(1 - pow(x / M_PI, 2))) / cosh(A);
}
#endif
static int build_filter(float *taps, uint32_t stride, uint32_t n_taps, uint32_t n_phases, double cutoff) static int build_filter(float *taps, uint32_t stride, uint32_t n_taps, uint32_t n_phases, double cutoff)
{ {
@ -77,7 +86,7 @@ static int build_filter(float *taps, uint32_t stride, uint32_t n_taps, uint32_t
/* exploit symmetry in filter taps */ /* exploit symmetry in filter taps */
taps[(n_phases - i) * stride + n_taps12 + j] = taps[(n_phases - i) * stride + n_taps12 + j] =
taps[i * stride + (n_taps12 - j - 1)] = taps[i * stride + (n_taps12 - j - 1)] =
cutoff * sinc(t * cutoff) * blackman(t, n_taps); cutoff * sinc(t * cutoff) * window_cosh(t, n_taps);
} }
} }
return 0; return 0;