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// Finite impulse response (FIR) resampler with adjustable FIR size
// Game_Music_Emu 0.6-pre
#ifndef FIR_RESAMPLER_H
#define FIR_RESAMPLER_H
#include "Resampler.h"
template<int width>
class Fir_Resampler;
// Use one of these typedefs
typedef Fir_Resampler< 8> Fir_Resampler_Fast;
typedef Fir_Resampler<16> Fir_Resampler_Norm;
typedef Fir_Resampler<24> Fir_Resampler_Good;
// Implementation
class Fir_Resampler_ : public Resampler {
protected:
virtual blargg_err_t set_rate_( double );
virtual void clear_();
protected:
enum { stereo = 2 };
enum { max_res = 32 }; // TODO: eliminate and keep impulses on freestore?
sample_t const* imp;
int const width_;
sample_t* impulses;
Fir_Resampler_( int width, sample_t [] );
};
// Width is number of points in FIR. More points give better quality and
// rolloff effectiveness, and take longer to calculate.
template<int width>
class Fir_Resampler : public Fir_Resampler_ {
enum { min_width = (width < 4 ? 4 : width) };
enum { adj_width = min_width / 4 * 4 + 2 };
enum { write_offset = adj_width * stereo };
short impulses [max_res * (adj_width + 2)];
public:
Fir_Resampler() : Fir_Resampler_( adj_width, impulses ) { }
protected:
virtual sample_t const* resample_( sample_t**, sample_t const*, sample_t const [], int );
};
template<int width>
Resampler::sample_t const* Fir_Resampler<width>::resample_( sample_t** out_,
sample_t const* out_end, sample_t const in [], int in_size )
{
in_size -= write_offset;
if ( in_size > 0 )
{
sample_t* BLARGG_RESTRICT out = *out_;
sample_t const* const in_end = in + in_size;
sample_t const* imp = this->imp;
do
{
// accumulate in extended precision
int pt = imp [0];
int l = pt * in [0];
int r = pt * in [1];
if ( out >= out_end )
break;
for ( int n = (adj_width - 2) / 2; n; --n )
{
pt = imp [1];
l += pt * in [2];
r += pt * in [3];
// pre-increment more efficient on some RISC processors
imp += 2;
pt = imp [0];
r += pt * in [5];
in += 4;
l += pt * in [0];
}
pt = imp [1];
l += pt * in [2];
r += pt * in [3];
// these two "samples" after the end of the impulse give the
// proper offsets to the next input sample and next impulse
in = (sample_t const*) ((char const*) in + imp [2]); // some negative value
imp = (sample_t const*) ((char const*) imp + imp [3]); // small positive or large negative
out [0] = sample_t (l >> 15);
out [1] = sample_t (r >> 15);
out += 2;
}
while ( in < in_end );
this->imp = imp;
*out_ = out;
}
return in;
}
#endif
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