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sinc.c
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sinc.c
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/* RetroArch - A frontend for libretro.
* Copyright (C) 2010-2013 - Hans-Kristian Arntzen
*
* RetroArch is free software: you can redistribute it and/or modify it under the terms
* of the GNU General Public License as published by the Free Software Found-
* ation, either version 3 of the License, or (at your option) any later version.
*
* RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with RetroArch.
* If not, see <http://www.gnu.org/licenses/>.
*/
// Bog-standard windowed SINC implementation.
// Only suitable as an upsampler, as there is no low-pass filter stage.
#include "resampler.h"
#include <math.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#ifndef RESAMPLER_TEST
#include "../general.h"
#else
#define RARCH_LOG(...)
#endif
#ifdef __SSE__
#include <xmmintrin.h>
#endif
// For the little amount of taps we're using,
// SSE1 is faster than AVX for some reason.
// AVX code is kept here though as by increasing number
// of sinc taps, the AVX code is clearly faster than SSE1.
#define ENABLE_AVX 0
#if defined(__AVX__) && ENABLE_AVX
#include <immintrin.h>
#endif
#define PHASE_BITS 16
#define SUBPHASE_BITS 10
#define PHASES (1 << (PHASE_BITS + SUBPHASE_BITS))
#define SIDELOBES 8
#define TAPS (SIDELOBES * 2)
#define CUTOFF 0.98
struct rarch_resampler
{
sample_t phase_table[1 << PHASE_BITS][TAPS];
sample_t buffer_l[2 * TAPS];
sample_t buffer_r[2 * TAPS];
unsigned ptr;
uint32_t time;
};
static inline double sinc(double val)
{
if (fabs(val) < 0.00001)
return 1.0;
else
return sin(val) / val;
}
static inline double lanzcos(double index)
{
return sinc(index);
}
static void init_sinc_table(rarch_resampler_t *resamp)
{
// Sinc phases: [..., p + 3, p + 2, p + 1, p + 0, p - 1, p - 2, p - 3, p - 4, ...]
for (int i = 0; i < (1 << PHASE_BITS); i++)
{
for (int j = 0; j < TAPS; j++)
{
double p = (double)i / (1 << PHASE_BITS);
double sinc_phase = M_PI * (p + (SIDELOBES - 1 - j));
float val = CUTOFF * sinc(CUTOFF * sinc_phase) * lanzcos(sinc_phase / SIDELOBES);
resamp->phase_table[i][j] = val;
}
}
}
// No memalign() for us on Win32 ...
static void *aligned_alloc__(size_t boundary, size_t size)
{
void *ptr = malloc(boundary + size + sizeof(uintptr_t));
if (!ptr)
return NULL;
uintptr_t addr = ((uintptr_t)ptr + sizeof(uintptr_t) + boundary) & ~(boundary - 1);
void **place = (void**)addr;
place[-1] = ptr;
return (void*)addr;
}
static void aligned_free__(void *ptr)
{
void **p = (void**)ptr;
free(p[-1]);
}
rarch_resampler_t *resampler_new(void)
{
rarch_resampler_t *re = (rarch_resampler_t*)aligned_alloc__(1024, sizeof(*re));
if (!re)
return NULL;
memset(re, 0, sizeof(*re));
init_sinc_table(re);
#if defined(__AVX__) && ENABLE_AVX
RARCH_LOG("Sinc resampler [AVX]\n");
#elif defined(__SSE__)
RARCH_LOG("Sinc resampler [SSE]\n");
#elif defined(HAVE_NEON)
RARCH_LOG("Sinc resampler [NEON]\n");
#else
RARCH_LOG("Sinc resampler [C]\n");
#endif
return re;
}
#if defined(__AVX__) && ENABLE_AVX
static void process_sinc(rarch_resampler_t *resamp, float *out_buffer)
{
__m256 sum_l = _mm256_setzero_ps();
__m256 sum_r = _mm256_setzero_ps();
const float *buffer_l = resamp->buffer_l + resamp->ptr;
const float *buffer_r = resamp->buffer_r + resamp->ptr;
unsigned phase = resamp->time >> SUBPHASE_BITS;
const float *phase_table = resamp->phase_table[phase];
for (unsigned i = 0; i < TAPS; i += 8)
{
__m256 buf_l = _mm256_loadu_ps(buffer_l + i);
__m256 buf_r = _mm256_loadu_ps(buffer_r + i);
__m256 sinc = _mm256_load_ps(phase_table + i);
sum_l = _mm256_add_ps(sum_l, _mm256_mul_ps(buf_l, sinc));
sum_r = _mm256_add_ps(sum_r, _mm256_mul_ps(buf_r, sinc));
}
// hadd on AVX is weird, and acts on low-lanes and high-lanes separately.
__m256 res_l = _mm256_hadd_ps(sum_l, sum_l);
__m256 res_r = _mm256_hadd_ps(sum_r, sum_r);
res_l = _mm256_hadd_ps(res_l, res_l);
res_r = _mm256_hadd_ps(res_r, res_r);
res_l = _mm256_add_ps(_mm256_permute2f128_ps(res_l, res_l, 1), res_l);
res_r = _mm256_add_ps(_mm256_permute2f128_ps(res_r, res_r, 1), res_r);
// This is optimized to mov %xmmN, [mem].
// There doesn't seem to be any _mm256_store_ss intrinsic.
_mm_store_ss(out_buffer + 0, _mm256_extractf128_ps(res_l, 0));
_mm_store_ss(out_buffer + 1, _mm256_extractf128_ps(res_r, 0));
}
#elif defined(__SSE__)
static void process_sinc(rarch_resampler_t *resamp, float *out_buffer)
{
__m128 sum_l = _mm_setzero_ps();
__m128 sum_r = _mm_setzero_ps();
const float *buffer_l = resamp->buffer_l + resamp->ptr;
const float *buffer_r = resamp->buffer_r + resamp->ptr;
unsigned phase = resamp->time >> SUBPHASE_BITS;
const float *phase_table = resamp->phase_table[phase];
for (unsigned i = 0; i < TAPS; i += 4)
{
__m128 buf_l = _mm_loadu_ps(buffer_l + i);
__m128 buf_r = _mm_loadu_ps(buffer_r + i);
__m128 sinc = _mm_load_ps(phase_table + i);
sum_l = _mm_add_ps(sum_l, _mm_mul_ps(buf_l, sinc));
sum_r = _mm_add_ps(sum_r, _mm_mul_ps(buf_r, sinc));
}
// Them annoying shuffles :V
// sum_l = { l3, l2, l1, l0 }
// sum_r = { r3, r2, r1, r0 }
__m128 sum = _mm_add_ps(_mm_shuffle_ps(sum_l, sum_r, _MM_SHUFFLE(1, 0, 1, 0)),
_mm_shuffle_ps(sum_l, sum_r, _MM_SHUFFLE(3, 2, 3, 2)));
// sum = { r1, r0, l1, l0 } + { r3, r2, l3, l2 }
// sum = { R1, R0, L1, L0 }
sum = _mm_add_ps(_mm_shuffle_ps(sum, sum, _MM_SHUFFLE(3, 3, 1, 1)), sum);
// sum = {R1, R1, L1, L1 } + { R1, R0, L1, L0 }
// sum = { X, R, X, L }
// Store L
_mm_store_ss(out_buffer + 0, sum);
// movehl { X, R, X, L } == { X, R, X, R }
_mm_store_ss(out_buffer + 1, _mm_movehl_ps(sum, sum));
}
#elif defined(HAVE_NEON)
void process_sinc_neon_asm(float *out, const float *left, const float *right, const float *coeff);
static void process_sinc(rarch_resampler_t *resamp, float *out_buffer)
{
const float *buffer_l = resamp->buffer_l + resamp->ptr;
const float *buffer_r = resamp->buffer_r + resamp->ptr;
unsigned phase = resamp->time >> SUBPHASE_BITS;
const float *phase_table = resamp->phase_table[phase];
process_sinc_neon_asm(out_buffer, buffer_l, buffer_r, phase_table);
}
#else // Plain ol' C99
static void process_sinc(rarch_resampler_t *resamp, float *out_buffer)
{
float sum_l = 0.0f;
float sum_r = 0.0f;
const float *buffer_l = resamp->buffer_l + resamp->ptr;
const float *buffer_r = resamp->buffer_r + resamp->ptr;
unsigned phase = resamp->time >> SUBPHASE_BITS;
const float *phase_table = resamp->phase_table[phase];
for (unsigned i = 0; i < TAPS; i++)
{
float sinc_val = phase_table[i];
sum_l += buffer_l[i] * sinc_val;
sum_r += buffer_r[i] * sinc_val;
}
out_buffer[0] = sum_l;
out_buffer[1] = sum_r;
}
#endif
void resampler_process(rarch_resampler_t *re, struct resampler_data *data)
{
// If data->ratio is < 1, we are downsampling.
// The sinc table is not set up for this, as it always assumes upsampling.
// Downsampling will work, but with some added noise due to aliasing might be present.
uint32_t ratio = PHASES / data->ratio;
const sample_t *input = data->data_in;
sample_t *output = data->data_out;
size_t frames = data->input_frames;
size_t out_frames = 0;
while (frames)
{
while (frames && re->time >= PHASES)
{
re->buffer_l[re->ptr + TAPS] = re->buffer_l[re->ptr] = *input++;
re->buffer_r[re->ptr + TAPS] = re->buffer_r[re->ptr] = *input++;
re->ptr = (re->ptr + 1) & (TAPS - 1);
re->time -= PHASES;
frames--;
}
while (re->time < PHASES)
{
process_sinc(re, output);
output += 2;
out_frames++;
re->time += ratio;
}
}
data->output_frames = out_frames;
}
void resampler_free(rarch_resampler_t *re)
{
aligned_free__(re);
}