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/* Simple resampler based on bsnes's ruby audio library */
#ifndef __HERMITE_RESAMPLER_H
#define __HERMITE_RESAMPLER_H
#include "resampler.h"
#undef CLAMP
#undef SHORT_CLAMP
#define CLAMP(x, low, high) (((x) > (high)) ? (high) : (((x) < (low)) ? (low) : (x)))
#define SHORT_CLAMP(n) ((short) CLAMP((n), -32768, 32767))
class HermiteResampler : public Resampler
{
protected:
float r_step;
float r_frac;
int r_left[4], r_right[4];
static inline float
hermite (float mu1, float a, float b, float c, float d)
{
float mu2, mu3, m0, m1, a0, a1, a2, a3;
mu2 = mu1 * mu1;
mu3 = mu2 * mu1;
m0 = (c - a) * 0.5;
m1 = (d - b) * 0.5;
a0 = +2 * mu3 - 3 * mu2 + 1;
a1 = mu3 - 2 * mu2 + mu1;
a2 = mu3 - mu2;
a3 = -2 * mu3 + 3 * mu2;
return (a0 * b) + (a1 * m0) + (a2 * m1) + (a3 * c);
}
public:
HermiteResampler (int num_samples) : Resampler (num_samples)
{
clear ();
}
~HermiteResampler ()
{
}
void
time_ratio (double ratio)
{
r_step = ratio;
clear ();
}
void
clear (void)
{
ring_buffer::clear ();
r_frac = 1.0;
r_left [0] = r_left [1] = r_left [2] = r_left [3] = 0;
r_right[0] = r_right[1] = r_right[2] = r_right[3] = 0;
}
void
read (short *data, int num_samples)
{
int i_position = start >> 1;
int max_samples = buffer_size >> 1;
short *internal_buffer = (short *) buffer;
int o_position = 0;
int consumed = 0;
while (o_position < num_samples && consumed < buffer_size)
{
int s_left = internal_buffer[i_position];
int s_right = internal_buffer[i_position + 1];
float hermite_val[2];
while (r_frac <= 1.0 && o_position < num_samples)
{
hermite_val[0] = hermite (r_frac, r_left [0], r_left [1], r_left [2], r_left [3]);
hermite_val[1] = hermite (r_frac, r_right[0], r_right[1], r_right[2], r_right[3]);
data[o_position] = SHORT_CLAMP (hermite_val[0]);
data[o_position + 1] = SHORT_CLAMP (hermite_val[1]);
o_position += 2;
r_frac += r_step;
}
if (r_frac > 1.0)
{
r_left [0] = r_left [1];
r_left [1] = r_left [2];
r_left [2] = r_left [3];
r_left [3] = s_left;
r_right[0] = r_right[1];
r_right[1] = r_right[2];
r_right[2] = r_right[3];
r_right[3] = s_right;
r_frac -= 1.0;
i_position += 2;
if (i_position >= max_samples)
i_position -= max_samples;
consumed += 2;
}
}
size -= consumed << 1;
start += consumed << 1;
if (start >= buffer_size)
start -= buffer_size;
}
inline int
avail (void)
{
return (int) floor (((size >> 2) - r_frac) / r_step) * 2;
}
};
#endif /* __HERMITE_RESAMPLER_H */
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