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172 lines
3.9 KiB
C
172 lines
3.9 KiB
C
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// Finite impulse response (FIR) resampler with adjustable FIR size
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// Game_Music_Emu https://bitbucket.org/mpyne/game-music-emu/
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#ifndef FIR_RESAMPLER_H
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#define FIR_RESAMPLER_H
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#include "blargg_common.h"
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#include <string.h>
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class Fir_Resampler_ {
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public:
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// Use Fir_Resampler<width> (below)
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// Set input/output resampling ratio and optionally low-pass rolloff and gain.
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// Returns actual ratio used (rounded to internal precision).
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double time_ratio( double factor, double rolloff = 0.999, double gain = 1.0 );
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// Current input/output ratio
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double ratio() const { return ratio_; }
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// Input
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typedef short sample_t;
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// Resize and clear input buffer
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blargg_err_t buffer_size( int );
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// Clear input buffer. At least two output samples will be available after
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// two input samples are written.
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void clear();
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// Number of input samples that can be written
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int max_write() const { return buf.end() - write_pos; }
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// Pointer to place to write input samples
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sample_t* buffer() { return write_pos; }
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// Notify resampler that 'count' input samples have been written
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void write( long count );
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// Number of input samples in buffer
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int written() const { return write_pos - &buf [write_offset]; }
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// Skip 'count' input samples. Returns number of samples actually skipped.
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int skip_input( long count );
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// Output
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// Number of extra input samples needed until 'count' output samples are available
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int input_needed( blargg_long count ) const;
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// Number of output samples available
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int avail() const { return avail_( write_pos - &buf [width_ * stereo] ); }
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public:
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~Fir_Resampler_();
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protected:
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enum { stereo = 2 };
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enum { max_res = 32 };
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blargg_vector<sample_t> buf;
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sample_t* write_pos;
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int res;
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int imp_phase;
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int const width_;
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int const write_offset;
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blargg_ulong skip_bits;
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int step;
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int input_per_cycle;
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double ratio_;
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sample_t* impulses;
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Fir_Resampler_( int width, sample_t* );
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int avail_( blargg_long input_count ) const;
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};
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// Width is number of points in FIR. Must be even and 4 or more. More points give
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// better quality and rolloff effectiveness, and take longer to calculate.
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template<int width>
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class Fir_Resampler : public Fir_Resampler_ {
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BOOST_STATIC_ASSERT( width >= 4 && width % 2 == 0 );
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short impulses [max_res] [width];
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public:
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Fir_Resampler() : Fir_Resampler_( width, impulses [0] ) { }
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// Read at most 'count' samples. Returns number of samples actually read.
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typedef short sample_t;
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int read( sample_t* out, blargg_long count );
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};
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// End of public interface
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inline void Fir_Resampler_::write( long count )
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{
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write_pos += count;
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assert( write_pos <= buf.end() );
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}
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template<int width>
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int Fir_Resampler<width>::read( sample_t* out_begin, blargg_long count )
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{
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sample_t* out = out_begin;
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const sample_t* in = buf.begin();
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sample_t* end_pos = write_pos;
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blargg_ulong skip = skip_bits >> imp_phase;
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sample_t const* imp = impulses [imp_phase];
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int remain = res - imp_phase;
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int const step = this->step;
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count >>= 1;
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if ( end_pos - in >= width * stereo )
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{
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end_pos -= width * stereo;
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do
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{
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count--;
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// accumulate in extended precision
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blargg_long l = 0;
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blargg_long r = 0;
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const sample_t* i = in;
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if ( count < 0 )
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break;
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for ( int n = width / 2; n; --n )
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{
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int pt0 = imp [0];
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l += pt0 * i [0];
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r += pt0 * i [1];
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int pt1 = imp [1];
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imp += 2;
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l += pt1 * i [2];
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r += pt1 * i [3];
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i += 4;
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}
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remain--;
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l >>= 15;
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r >>= 15;
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in += (skip * stereo) & stereo;
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skip >>= 1;
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in += step;
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if ( !remain )
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{
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imp = impulses [0];
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skip = skip_bits;
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remain = res;
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}
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out [0] = (sample_t) l;
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out [1] = (sample_t) r;
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out += 2;
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}
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while ( in <= end_pos );
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}
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imp_phase = res - remain;
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int left = write_pos - in;
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write_pos = &buf [left];
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memmove( buf.begin(), in, left * sizeof *in );
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return out - out_begin;
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}
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#endif
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