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https://github.com/dborth/snes9xgx.git
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145 lines
4.2 KiB
C++
145 lines
4.2 KiB
C++
/* Simple resampler based on bsnes's ruby audio library */
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#ifndef __HERMITE_RESAMPLER_H
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#define __HERMITE_RESAMPLER_H
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#include "resampler.h"
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#undef CLAMP
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#undef SHORT_CLAMP
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#define CLAMP(x, low, high) (((x) > (high)) ? (high) : (((x) < (low)) ? (low) : (x)))
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#define SHORT_CLAMP(n) ((short) CLAMP((n), -32768, 32767))
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class HermiteResampler : public Resampler
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{
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protected:
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double r_step;
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double r_frac;
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int r_left[4], r_right[4];
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double
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hermite (double mu1, double a, double b, double c, double d)
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{
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const double tension = 0.0; //-1 = low, 0 = normal, 1 = high
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const double bias = 0.0; //-1 = left, 0 = even, 1 = right
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double mu2, mu3, m0, m1, a0, a1, a2, a3;
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mu2 = mu1 * mu1;
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mu3 = mu2 * mu1;
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m0 = (b - a) * (1 + bias) * (1 - tension) / 2;
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m0 += (c - b) * (1 - bias) * (1 - tension) / 2;
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m1 = (c - b) * (1 + bias) * (1 - tension) / 2;
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m1 += (d - c) * (1 - bias) * (1 - tension) / 2;
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a0 = +2 * mu3 - 3 * mu2 + 1;
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a1 = mu3 - 2 * mu2 + mu1;
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a2 = mu3 - mu2;
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a3 = -2 * mu3 + 3 * mu2;
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return (a0 * b) + (a1 * m0) + (a2 * m1) + (a3 * c);
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}
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public:
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HermiteResampler (int num_samples) : Resampler (num_samples)
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{
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clear ();
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}
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~HermiteResampler ()
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{
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}
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void
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time_ratio (double ratio)
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{
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r_step = ratio;
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clear ();
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}
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void
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clear (void)
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{
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ring_buffer::clear ();
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r_frac = 1.0;
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r_left [0] = r_left [1] = r_left [2] = r_left [3] = 0;
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r_right[0] = r_right[1] = r_right[2] = r_right[3] = 0;
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}
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void
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read (short *data, int num_samples)
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{
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int i_position = start >> 1;
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short *internal_buffer = (short *) buffer;
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int o_position = 0;
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int consumed = 0;
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while (o_position < num_samples && consumed < buffer_size)
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{
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int s_left = internal_buffer[i_position];
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int s_right = internal_buffer[i_position + 1];
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int max_samples = buffer_size >> 1;
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const double margin_of_error = 1.0e-10;
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if (fabs(r_step - 1.0) < margin_of_error)
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{
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data[o_position] = (short) s_left;
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data[o_position + 1] = (short) s_right;
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o_position += 2;
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i_position += 2;
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if (i_position >= max_samples)
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i_position -= max_samples;
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consumed += 2;
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continue;
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}
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while (r_frac <= 1.0 && o_position < num_samples)
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{
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data[o_position] = SHORT_CLAMP (hermite (r_frac, r_left [0], r_left [1], r_left [2], r_left [3]));
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data[o_position + 1] = SHORT_CLAMP (hermite (r_frac, r_right[0], r_right[1], r_right[2], r_right[3]));
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o_position += 2;
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r_frac += r_step;
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}
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if (r_frac > 1.0)
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{
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r_left [0] = r_left [1];
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r_left [1] = r_left [2];
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r_left [2] = r_left [3];
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r_left [3] = s_left;
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r_right[0] = r_right[1];
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r_right[1] = r_right[2];
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r_right[2] = r_right[3];
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r_right[3] = s_right;
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r_frac -= 1.0;
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i_position += 2;
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if (i_position >= max_samples)
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i_position -= max_samples;
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consumed += 2;
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}
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}
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size -= consumed << 1;
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start += consumed << 1;
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if (start >= buffer_size)
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start -= buffer_size;
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}
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inline int
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avail (void)
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{
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return (int) floor (((size >> 2) - r_frac) / r_step) * 2;
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}
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};
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#endif /* __HERMITE_RESAMPLER_H */
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