rockbox/apps/codecs/libgme/resampler.h

// Combination of Downsampler and Blip_Buffer mixing. Used by Sega FM emulators.

// Game_Music_Emu 0.5.5
#ifndef RESAMPLER_H
#define RESAMPLER_H

#include "blargg_common.h"
#include "multi_buffer.h"

typedef short sample_t;

enum { stereo = 2 };
enum { max_buf_size = 3960 };
enum { max_resampler_size = 5942 };
enum { write_offset = 8 * stereo };
enum { gain_bits = 14 };

struct Resampler {
    int (*callback)( void*, blip_time_t, int, sample_t* );
    void* callback_data;

    int sample_buffer_size;
    int sample_buf_size;
    int oversamples_per_frame;
    int buf_pos;
    int resampler_size;
    int gain_;

    int buffer_size;
    int write_pos;

    int pos;
    int step;

    int rate_;

    sample_t sample_buf [max_buf_size];
    sample_t buf [max_resampler_size];   // Internal resampler
};

static inline void Resampler_init( struct Resampler* this )
{
    this->pos = 0;
    this->write_pos = 0;
    this->rate_     = 0;
    this->sample_buf_size = 0;
    this->sample_buffer_size = 0;
    this->oversamples_per_frame = 0;
}

blargg_err_t Resampler_reset( struct Resampler* this, int max_pairs );
void Resampler_resize( struct Resampler* this, int pairs_per_frame );
void Resampler_play( struct Resampler* this, int count, sample_t* out, struct Blip_Buffer* );

static inline void Resampler_set_callback(struct Resampler* this, int (*func)( void*, blip_time_t, int, sample_t* ), void* user_data )
{
    this->callback = func;
    this->callback_data = user_data;
}

blargg_err_t Resampler_setup( struct Resampler* this, int fm_rate, int fm_gain, int rate, int gain );

static inline void Resampler_clear( struct Resampler* this )
{
    this->buf_pos = this->sample_buf_size;

    this->pos = 0;
    this->write_pos = 0;
}

static inline int Resampler_rate( struct Resampler* this )
{
    return this->rate_;
}

#endif