SDLPAL/resampler.c

#include <stdlib.h>
#include <string.h>
#define _USE_MATH_DEFINES
#include <math.h>
#if !defined(__MINGW32__) && !defined(__EMSCRIPTEN__)
#if (defined(_M_IX86) || defined(__i386__) || defined(_M_X64) || defined(__amd64__))
#include <xmmintrin.h>
#define RESAMPLER_SSE
#endif
#endif

#ifdef _MSC_VER
#define ALIGNED     _declspec(align(16))
#else
#define ALIGNED     __attribute__((aligned(16)))
#endif

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#include "resampler.h"

enum { RESAMPLER_SHIFT = 10 };
enum { RESAMPLER_RESOLUTION = 1 << RESAMPLER_SHIFT };
enum { SINC_WIDTH = 16 };
enum { SINC_SAMPLES = RESAMPLER_RESOLUTION * SINC_WIDTH };
enum { CUBIC_SAMPLES = RESAMPLER_RESOLUTION * 4 };

ALIGNED static float cubic_lut[CUBIC_SAMPLES];

static float sinc_lut[SINC_SAMPLES + 1];
static float window_lut[SINC_SAMPLES + 1];

enum { resampler_buffer_size = SINC_WIDTH * 4 };

typedef struct resampler
{
	int write_pos, write_filled;
	int read_pos, read_filled;
	unsigned int phase;
	unsigned int phase_inc;
	unsigned int inv_phase;
	unsigned int inv_phase_inc;
	unsigned char quality;
	signed char delay_added;
	signed char delay_removed;
	float last_amp;
	float accumulator;
	float buffer_in[resampler_buffer_size * 2];
	float buffer_out[resampler_buffer_size + SINC_WIDTH * 2 - 1];
} resampler;

static int fEqual(const float b, const float a)
{
    return fabs(a - b) < 1.0e-6;
}

static float sinc(float x)
{
    return fEqual(x, 0.0f) ? 1.0f : (float)(sin(x * M_PI) / (x * M_PI));
}

typedef int (*resampler_run)(resampler *, float **, float *);

#ifdef RESAMPLER_SSE
# ifdef _MSC_VER
#  include <intrin.h>
#  pragma warning(disable:4244)
# elif defined(__clang__) || defined(__GNUC__)
static inline void __cpuid(int *data, int selector)
{
#  if defined(__PIC__) && defined(__i386__)
    asm("xchgl %%ebx, %%esi; cpuid; xchgl %%ebx, %%esi"
        : "=a" (data[0]),
        "=S" (data[1]),
        "=c" (data[2]),
        "=d" (data[3])
        : "0" (selector));
#  elif defined(__PIC__) && defined(__amd64__)
    asm("xchg{q} {%%}rbx, %q1; cpuid; xchg{q} {%%}rbx, %q1"
        : "=a" (data[0]),
        "=&r" (data[1]),
        "=c" (data[2]),
        "=d" (data[3])
        : "0" (selector));
#  else
    asm("cpuid"
        : "=a" (data[0]),
        "=b" (data[1]),
        "=c" (data[2]),
        "=d" (data[3])
        : "0" (selector));
#  endif
}
# else
#  define __cpuid(a,b) memset((a), 0, sizeof(int) * 4)
# endif

static int query_cpu_feature_sse() {
    int buffer[4];
    __cpuid(buffer,1);
    if ((buffer[3]&(1<<25)) == 0) return 0;
    return 1;
}

static int resampler_run_blep_sse(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 1;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		float last_amp = r->last_amp;
		int inv_phase = r->inv_phase;
		int inv_phase_inc = r->inv_phase_inc;

		const int step = RESAMPLER_RESOLUTION;

		do
		{
			// accumulate in extended precision
			float kernel_sum = 0.0;
			__m128 kernel[SINC_WIDTH / 2];
			__m128 temp1, temp2;
			__m128 samplex;
			float sample;
			float *kernelf = (float*)(&kernel);
			int i = SINC_WIDTH;

			if (out + SINC_WIDTH * 2 > out_end)
				break;

			for (; i >= -SINC_WIDTH + 1; --i)
			{
				int pos = i * step;
				int abs_pos = abs(inv_phase - pos);
				kernel_sum += kernelf[i + SINC_WIDTH - 1] = sinc_lut[abs_pos] * window_lut[abs_pos];
			}
			sample = *in++ - last_amp;
			last_amp += sample;
			sample /= kernel_sum;
			samplex = _mm_set1_ps(sample);
			for (i = 0; i < SINC_WIDTH / 2; ++i)
			{
				temp1 = _mm_load_ps((const float *)(kernel + i));
				temp1 = _mm_mul_ps(temp1, samplex);
				temp2 = _mm_loadu_ps((const float *)out + i * 4);
				temp1 = _mm_add_ps(temp1, temp2);
				_mm_storeu_ps((float *)out + i * 4, temp1);
			}

			inv_phase += inv_phase_inc;

			out += inv_phase >> RESAMPLER_SHIFT;

			inv_phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->inv_phase = inv_phase;
		r->last_amp = last_amp;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_cubic_sse(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 4;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		do
		{
			__m128 temp1, temp2;
			__m128 samplex = _mm_setzero_ps();

			if (out >= out_end)
				break;

			temp1 = _mm_loadu_ps((const float *)(in));
			temp2 = _mm_load_ps((const float *)(cubic_lut + phase * 4));
			temp1 = _mm_mul_ps(temp1, temp2);
			samplex = _mm_add_ps(samplex, temp1);
			temp1 = _mm_movehl_ps(temp1, samplex);
			samplex = _mm_add_ps(samplex, temp1);
			temp1 = samplex;
			temp1 = _mm_shuffle_ps(temp1, samplex, _MM_SHUFFLE(0, 0, 0, 1));
			samplex = _mm_add_ps(samplex, temp1);
			_mm_store_ss(out, samplex);
			++out;

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_sinc_sse(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= SINC_WIDTH * 2;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		int step = phase_inc > RESAMPLER_RESOLUTION ? RESAMPLER_RESOLUTION * RESAMPLER_RESOLUTION / phase_inc : RESAMPLER_RESOLUTION;
		int window_step = RESAMPLER_RESOLUTION;

		do
		{
			// accumulate in extended precision
			float kernel_sum = 0.0;
			__m128 kernel[SINC_WIDTH / 2];
			__m128 temp1, temp2;
			__m128 samplex = _mm_setzero_ps();
			float *kernelf = (float*)(&kernel);
			int i = SINC_WIDTH;
			int phase_adj = phase * step / RESAMPLER_RESOLUTION;

			if (out >= out_end)
				break;

			for (; i >= -SINC_WIDTH + 1; --i)
			{
				int pos = i * step;
				int window_pos = i * window_step;
				kernel_sum += kernelf[i + SINC_WIDTH - 1] = sinc_lut[abs(phase_adj - pos)] * window_lut[abs(phase - window_pos)];
			}
			for (i = 0; i < SINC_WIDTH / 2; ++i)
			{
				temp1 = _mm_loadu_ps((const float *)(in + i * 4));
				temp2 = _mm_load_ps((const float *)(kernel + i));
				temp1 = _mm_mul_ps(temp1, temp2);
				samplex = _mm_add_ps(samplex, temp1);
			}
			kernel_sum = 1.0f / kernel_sum;
			temp1 = _mm_movehl_ps(temp1, samplex);
			samplex = _mm_add_ps(samplex, temp1);
			temp1 = samplex;
			temp1 = _mm_shuffle_ps(temp1, samplex, _MM_SHUFFLE(0, 0, 0, 1));
			samplex = _mm_add_ps(samplex, temp1);
			temp1 = _mm_set_ss(kernel_sum);
			samplex = _mm_mul_ps(samplex, temp1);
			_mm_store_ss(out, samplex);
			++out;

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

#endif

static int resampler_run_zoh(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 1;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		do
		{
			float sample;

			if (out >= out_end)
				break;

			sample = *in;
			*out++ = sample;

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = (unsigned short)phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_blep_c(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 1;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		float last_amp = r->last_amp;
		int inv_phase = r->inv_phase;
		int inv_phase_inc = r->inv_phase_inc;

		const int step = RESAMPLER_RESOLUTION;

		do
		{
			float kernel[SINC_WIDTH * 2], kernel_sum = 0.0;
			int i = SINC_WIDTH;
			float sample;

			if (out + SINC_WIDTH * 2 > out_end)
				break;

			for (; i >= -SINC_WIDTH + 1; --i)
			{
				int pos = i * step;
				int abs_pos = abs(inv_phase - pos);
				kernel_sum += kernel[i + SINC_WIDTH - 1] = sinc_lut[abs_pos] * window_lut[abs_pos];
			}
			sample = *in++ - last_amp;
			last_amp += sample;
			sample /= kernel_sum;
			for (i = 0; i < SINC_WIDTH * 2; ++i)
				out[i] += sample * kernel[i];

			inv_phase += inv_phase_inc;

			out += inv_phase >> RESAMPLER_SHIFT;

			inv_phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->inv_phase = inv_phase;
		r->last_amp = last_amp;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_linear(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 2;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		do
		{
			float sample;

			if (out >= out_end)
				break;

			sample = in[0] + (in[1] - in[0]) * ((float)phase / RESAMPLER_RESOLUTION);
			*out++ = sample;

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_cubic_c(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= 4;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		do
		{
			float * kernel;
			int i;
			float sample;

			if (out >= out_end)
				break;

			kernel = cubic_lut + phase * 4;

			for (sample = 0, i = 0; i < 4; ++i)
				sample += in[i] * kernel[i];
			*out++ = sample;

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static int resampler_run_sinc_c(resampler * r, float ** out_, float * out_end)
{
	int in_size = r->write_filled;
	float const* in_ = r->buffer_in + resampler_buffer_size + r->write_pos - r->write_filled;
	int used = 0;
	in_size -= SINC_WIDTH * 2;
	if (in_size > 0)
	{
		float* out = *out_;
		float const* in = in_;
		float const* const in_end = in + in_size;
		int phase = r->phase;
		int phase_inc = r->phase_inc;

		int step = phase_inc > RESAMPLER_RESOLUTION ? RESAMPLER_RESOLUTION * RESAMPLER_RESOLUTION / phase_inc : RESAMPLER_RESOLUTION;
		int window_step = RESAMPLER_RESOLUTION;

		do
		{
			float kernel[SINC_WIDTH * 2], kernel_sum = 0.0;
			int i = SINC_WIDTH;
			int phase_adj = phase * step / RESAMPLER_RESOLUTION;
			float sample;

			if (out >= out_end)
				break;

			for (; i >= -SINC_WIDTH + 1; --i)
			{
				int pos = i * step;
				int window_pos = i * window_step;
				kernel_sum += kernel[i + SINC_WIDTH - 1] = sinc_lut[abs(phase_adj - pos)] * window_lut[abs(phase - window_pos)];
			}
			for (sample = 0, i = 0; i < SINC_WIDTH * 2; ++i)
				sample += in[i] * kernel[i];
			*out++ = (float)(sample / kernel_sum);

			phase += phase_inc;

			in += phase >> RESAMPLER_SHIFT;

			phase &= RESAMPLER_RESOLUTION - 1;
		} while (in < in_end);

		r->phase = phase;
		*out_ = out;

		used = (int)(in - in_);

		r->write_filled -= used;
	}

	return used;
}

static resampler_run resampler_run_blep = resampler_run_blep_c;
static resampler_run resampler_run_cubic = resampler_run_cubic_c;
static resampler_run resampler_run_sinc = resampler_run_sinc_c;

void resampler_init(void)
{
    unsigned i;
    double dx = (float)(SINC_WIDTH) / SINC_SAMPLES, x = 0.0;
    for (i = 0; i < SINC_SAMPLES + 1; ++i, x += dx)
    {
        float y = x / SINC_WIDTH;
#if 0
        // Blackman
        float window = 0.42659 - 0.49656 * cos(M_PI + M_PI * y) + 0.076849 * cos(2.0 * M_PI * y);
#elif 1
        // Nuttal 3 term
        float window = 0.40897 + 0.5 * cos(M_PI * y) + 0.09103 * cos(2.0 * M_PI * y);
#elif 0
        // C.R.Helmrich's 2 term window
        float window = 0.79445 * cos(0.5 * M_PI * y) + 0.20555 * cos(1.5 * M_PI * y);
#elif 0
        // Lanczos
        float window = sinc(y);
#endif
        sinc_lut[i] = fabs(x) < SINC_WIDTH ? sinc(x) : 0.0;
        window_lut[i] = window;
    }
    dx = 1.0 / (float)(RESAMPLER_RESOLUTION);
    x = 0.0;
    for (i = 0; i < RESAMPLER_RESOLUTION; ++i, x += dx)
    {
        cubic_lut[i*4]   = (float)(-0.5 * x * x * x +       x * x - 0.5 * x);
        cubic_lut[i*4+1] = (float)( 1.5 * x * x * x - 2.5 * x * x           + 1.0);
        cubic_lut[i*4+2] = (float)(-1.5 * x * x * x + 2.0 * x * x + 0.5 * x);
        cubic_lut[i*4+3] = (float)( 0.5 * x * x * x - 0.5 * x * x);
    }
#ifdef RESAMPLER_SSE
	if (query_cpu_feature_sse())
	{
		resampler_run_blep = resampler_run_blep_sse;
		resampler_run_cubic = resampler_run_cubic_sse;
		resampler_run_sinc = resampler_run_sinc_sse;
	}
#endif
}

void * resampler_create(void)
{
    resampler * r = ( resampler * ) malloc( sizeof(resampler) );
    if ( !r ) return 0;

    r->write_pos = SINC_WIDTH - 1;
    r->write_filled = 0;
    r->read_pos = 0;
    r->read_filled = 0;
    r->phase = 0;
    r->phase_inc = 0;
    r->inv_phase = 0;
    r->inv_phase_inc = 0;
    r->quality = RESAMPLER_QUALITY_MAX;
    r->delay_added = -1;
    r->delay_removed = -1;
    r->last_amp = 0;
    r->accumulator = 0;
    memset( r->buffer_in, 0, sizeof(r->buffer_in) );
    memset( r->buffer_out, 0, sizeof(r->buffer_out) );

    return r;
}

void resampler_delete(void * _r)
{
    free( _r );
}

void * resampler_dup(const void * _r)
{
    const resampler * r_in = ( const resampler * ) _r;
    resampler * r_out = ( resampler * ) malloc( sizeof(resampler) );
    if ( !r_out ) return 0;

    r_out->write_pos = r_in->write_pos;
    r_out->write_filled = r_in->write_filled;
    r_out->read_pos = r_in->read_pos;
    r_out->read_filled = r_in->read_filled;
    r_out->phase = r_in->phase;
    r_out->phase_inc = r_in->phase_inc;
    r_out->inv_phase = r_in->inv_phase;
    r_out->inv_phase_inc = r_in->inv_phase_inc;
    r_out->quality = r_in->quality;
    r_out->delay_added = r_in->delay_added;
    r_out->delay_removed = r_in->delay_removed;
    r_out->last_amp = r_in->last_amp;
    r_out->accumulator = r_in->accumulator;
    memcpy( r_out->buffer_in, r_in->buffer_in, sizeof(r_in->buffer_in) );
    memcpy( r_out->buffer_out, r_in->buffer_out, sizeof(r_in->buffer_out) );

    return r_out;
}

void resampler_dup_inplace(void *_d, const void *_s)
{
    const resampler * r_in = ( const resampler * ) _s;
    resampler * r_out = ( resampler * ) _d;

    r_out->write_pos = r_in->write_pos;
    r_out->write_filled = r_in->write_filled;
    r_out->read_pos = r_in->read_pos;
    r_out->read_filled = r_in->read_filled;
    r_out->phase = r_in->phase;
    r_out->phase_inc = r_in->phase_inc;
    r_out->inv_phase = r_in->inv_phase;
    r_out->inv_phase_inc = r_in->inv_phase_inc;
    r_out->quality = r_in->quality;
    r_out->delay_added = r_in->delay_added;
    r_out->delay_removed = r_in->delay_removed;
    r_out->last_amp = r_in->last_amp;
    r_out->accumulator = r_in->accumulator;
    memcpy( r_out->buffer_in, r_in->buffer_in, sizeof(r_in->buffer_in) );
    memcpy( r_out->buffer_out, r_in->buffer_out, sizeof(r_in->buffer_out) );
}

void resampler_set_quality(void *_r, int quality)
{
    resampler * r = ( resampler * ) _r;
    if (quality < RESAMPLER_QUALITY_MIN)
        quality = RESAMPLER_QUALITY_MIN;
    else if (quality > RESAMPLER_QUALITY_MAX)
        quality = RESAMPLER_QUALITY_MAX;
    if ( r->quality != quality )
    {
        if ( quality == RESAMPLER_QUALITY_BLEP || r->quality == RESAMPLER_QUALITY_BLEP )
        {
            r->read_pos = 0;
            r->read_filled = 0;
            r->last_amp = 0;
            r->accumulator = 0;
            memset( r->buffer_out, 0, sizeof(r->buffer_out) );
        }
        r->delay_added = -1;
        r->delay_removed = -1;
    }
    r->quality = (unsigned char)quality;
}

int resampler_get_free_count(void *_r)
{
    resampler * r = ( resampler * ) _r;
    return resampler_buffer_size - r->write_filled;
}

static int resampler_min_filled(resampler *r)
{
    switch (r->quality)
    {
    default:
    case RESAMPLER_QUALITY_ZOH:
    case RESAMPLER_QUALITY_BLEP:
        return 1;
            
    case RESAMPLER_QUALITY_LINEAR:
        return 2;
            
    case RESAMPLER_QUALITY_CUBIC:
        return 4;
            
    case RESAMPLER_QUALITY_SINC:
        return SINC_WIDTH * 2;
    }
}

static int resampler_input_delay(resampler *r)
{
    switch (r->quality)
    {
    default:
    case RESAMPLER_QUALITY_ZOH:
    case RESAMPLER_QUALITY_BLEP:
    case RESAMPLER_QUALITY_LINEAR:
        return 0;
            
    case RESAMPLER_QUALITY_CUBIC:
        return 1;
            
    case RESAMPLER_QUALITY_SINC:
        return SINC_WIDTH - 1;
    }
}

static int resampler_output_delay(resampler *r)
{
    switch (r->quality)
    {
    default:
    case RESAMPLER_QUALITY_ZOH:
    case RESAMPLER_QUALITY_LINEAR:
    case RESAMPLER_QUALITY_CUBIC:
    case RESAMPLER_QUALITY_SINC:
        return 0;
            
    case RESAMPLER_QUALITY_BLEP:
        return SINC_WIDTH - 1;
    }
}

int resampler_ready(void *_r)
{
    resampler * r = ( resampler * ) _r;
    return r->write_filled > resampler_min_filled(r);
}

void resampler_clear(void *_r)
{
    resampler * r = ( resampler * ) _r;
    r->write_pos = SINC_WIDTH - 1;
    r->write_filled = 0;
    r->read_pos = 0;
    r->read_filled = 0;
    r->phase = 0;
    r->delay_added = -1;
    r->delay_removed = -1;
    memset(r->buffer_in, 0, (SINC_WIDTH - 1) * sizeof(r->buffer_in[0]));
    memset(r->buffer_in + resampler_buffer_size, 0, (SINC_WIDTH - 1) * sizeof(r->buffer_in[0]));
    if (r->quality == RESAMPLER_QUALITY_BLEP)
        memset(r->buffer_out, 0, sizeof(r->buffer_out));
}

void resampler_set_rate(void *_r, double new_factor)
{
    resampler * r = ( resampler * ) _r;
    r->phase_inc = (int)( new_factor * RESAMPLER_RESOLUTION );
    new_factor = 1.0 / new_factor;
    r->inv_phase_inc = (int)( new_factor * RESAMPLER_RESOLUTION );
}

void resampler_write_sample(void *_r, short s)
{
    resampler * r = ( resampler * ) _r;

    if ( r->delay_added < 0 )
    {
        r->delay_added = 0;
        r->write_filled = resampler_input_delay( r );
    }
    
    if ( r->write_filled < resampler_buffer_size )
    {
        float s32 = s;
        s32 *= 256.0;

        r->buffer_in[ r->write_pos ] = s32;
        r->buffer_in[ r->write_pos + resampler_buffer_size ] = s32;

        ++r->write_filled;

        r->write_pos = ( r->write_pos + 1 ) % resampler_buffer_size;
    }
}

void resampler_write_sample_fixed(void *_r, int s, unsigned char depth)
{
    resampler * r = ( resampler * ) _r;
    
    if ( r->delay_added < 0 )
    {
        r->delay_added = 0;
        r->write_filled = resampler_input_delay( r );
    }
    
    if ( r->write_filled < resampler_buffer_size )
    {
        float s32 = s;
        s32 /= (double)(1 << (depth - 1));
        
        r->buffer_in[ r->write_pos ] = s32;
        r->buffer_in[ r->write_pos + resampler_buffer_size ] = s32;
        
        ++r->write_filled;
        
        r->write_pos = ( r->write_pos + 1 ) % resampler_buffer_size;
    }
}

static void resampler_fill(resampler * r)
{
    int min_filled = resampler_min_filled(r);
    int quality = r->quality;
    while ( r->write_filled > min_filled &&
            r->read_filled < resampler_buffer_size )
    {
        int write_pos = ( r->read_pos + r->read_filled ) % resampler_buffer_size;
        int write_size = resampler_buffer_size - write_pos;
        float * out = r->buffer_out + write_pos;
        if ( write_size > ( resampler_buffer_size - r->read_filled ) )
            write_size = resampler_buffer_size - r->read_filled;
        switch (quality)
        {
        case RESAMPLER_QUALITY_ZOH:
            resampler_run_zoh( r, &out, out + write_size );
            break;
                
        case RESAMPLER_QUALITY_BLEP:
        {
            int used;
            int write_extra = 0;
            if ( write_pos >= r->read_pos )
                write_extra = r->read_pos;
            if ( write_extra > SINC_WIDTH * 2 - 1 )
                write_extra = SINC_WIDTH * 2 - 1;
            memcpy( r->buffer_out + resampler_buffer_size, r->buffer_out, write_extra * sizeof(r->buffer_out[0]) );
            used = resampler_run_blep( r, &out, out + write_size + write_extra );
            memcpy( r->buffer_out, r->buffer_out + resampler_buffer_size, write_extra * sizeof(r->buffer_out[0]) );
            if (!used)
                return;
            break;
        }
                
        case RESAMPLER_QUALITY_LINEAR:
            resampler_run_linear( r, &out, out + write_size );
            break;
                
        case RESAMPLER_QUALITY_CUBIC:
            resampler_run_cubic( r, &out, out + write_size );
            break;
                
        case RESAMPLER_QUALITY_SINC:
            resampler_run_sinc( r, &out, out + write_size );
            break;
        }
        r->read_filled += out - r->buffer_out - write_pos;
    }
}

static void resampler_fill_and_remove_delay(resampler * r)
{
    resampler_fill( r );
    if ( r->delay_removed < 0 )
    {
        int delay = resampler_output_delay( r );
        r->delay_removed = 0;
        while ( delay-- )
            resampler_remove_sample( r );
    }
}

int resampler_get_sample_count(void *_r)
{
    resampler * r = ( resampler * ) _r;
    if ( r->read_filled < 1 && (r->quality != RESAMPLER_QUALITY_BLEP || r->inv_phase_inc))
        resampler_fill_and_remove_delay( r );
    return r->read_filled;
}

int resampler_get_sample(void *_r)
{
    resampler * r = ( resampler * ) _r;
    if ( r->read_filled < 1 && r->phase_inc)
        resampler_fill_and_remove_delay( r );
    if ( r->read_filled < 1 )
        return 0;
    if ( r->quality == RESAMPLER_QUALITY_BLEP )
        return (int)(r->buffer_out[ r->read_pos ] + r->accumulator);
    else
        return (int)r->buffer_out[ r->read_pos ];
}

void resampler_remove_sample(void *_r)
{
    resampler * r = ( resampler * ) _r;
    if ( r->read_filled > 0 )
    {
        if ( r->quality == RESAMPLER_QUALITY_BLEP )
        {
            r->accumulator += r->buffer_out[ r->read_pos ];
            r->buffer_out[ r->read_pos ] = 0;
            r->accumulator -= r->accumulator * (1.0 / 8192.0);
            if (fabs(r->accumulator) < 1e-20)
                r->accumulator = 0;
        }
        --r->read_filled;
        r->read_pos = ( r->read_pos + 1 ) % resampler_buffer_size;
    }
}

/* Get a 16-bit sample with saturation */
short resampler_get_and_remove_sample(void *_r)
{
	int sample = resampler_get_sample(_r) >> 8;
	resampler_remove_sample(_r);
	if (sample > 32767)
		return 32767;
	else if (sample < -32768)
		return -32768;
	else
		return (short)sample;
}