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https://github.com/libretro/RetroArch
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Rework SINC resampler. Use Kaiser window.
This commit is contained in:
Themaister
parent
252a917b7e
commit
578a47d73d
103
audio/sinc.c
103
audio/sinc.c
@ -14,7 +14,7 @@
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*/
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// Bog-standard windowed SINC implementation.
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// Only suitable as an upsampler, as there is no low-pass filter stage.
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// Only suitable as an upsampler, as cutoff frequency isn't dynamically configurable (yet).
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#include "resampler.h"
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#include "../performance.h"
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@ -33,16 +33,45 @@
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#include <xmmintrin.h>
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#endif
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#ifdef SINC_LOWER_QUALITY
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// Rough SNR values for upsampling:
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// LOWEST: 40 dB
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// LOWER: 55 dB
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// NORMAL: 70 dB
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// HIGHER: 110 dB
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// HIGHEST: 140 dB
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// TODO, make all this more configurable.
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#if defined(SINC_LOWEST_QUALITY)
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#define SINC_WINDOW_LANCZOS
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#define CUTOFF 0.98
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#define PHASE_BITS 11
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#define SIDELOBES 2
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#define ENABLE_AVX 0
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#elif defined(SINC_LOWER_QUALITY)
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#define SINC_WINDOW_LANCZOS
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#define CUTOFF 0.98
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#define PHASE_BITS 12
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#define SIDELOBES 4
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#define ENABLE_AVX 0
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#elif defined(SINC_HIGHER_QUALITY)
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#define SINC_WINDOW_KAISER
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#define SINC_WINDOW_KAISER_BETA 10.5
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#define CUTOFF 0.90
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#define PHASE_BITS 16
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#define SIDELOBES 32
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#define ENABLE_AVX 1
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#else
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#elif defined(SINC_HIGHEST_QUALITY)
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#define SINC_WINDOW_KAISER
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#define SINC_WINDOW_KAISER_BETA 14.5
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#define CUTOFF 0.95
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#define PHASE_BITS 16
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#define SIDELOBES 128
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#define ENABLE_AVX 1
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#else
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#define SINC_WINDOW_KAISER
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#define SINC_WINDOW_KAISER_BETA 5.5
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#define CUTOFF 0.825
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#define PHASE_BITS 14
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#define SIDELOBES 8
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#define ENABLE_AVX 0
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#endif
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@ -60,7 +89,6 @@
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#define PHASES (1 << (PHASE_BITS + SUBPHASE_BITS))
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#define TAPS (SIDELOBES * 2)
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#define CUTOFF 0.98
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typedef struct rarch_sinc_resampler
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{
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@ -80,23 +108,62 @@ static inline double sinc(double val)
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return sin(val) / val;
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}
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static inline double lanzcos(double index)
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#if defined(SINC_WINDOW_LANCZOS)
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static inline double window_function(double index)
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{
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return sinc(index);
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return sinc(M_PI * index);
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}
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#elif defined(SINC_WINDOW_KAISER)
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// Modified Bessel function of first order.
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// Check Wiki for mathematical definition ...
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static inline double besseli0(double x)
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{
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double sum = 0.0;
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double factorial = 1.0;
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double factorial_mult = 0.0;
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double x_pow = 1.0;
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double two_div_pow = 1.0;
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// Approximate. This is an infinite sum.
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// Luckily, it converges rather fast.
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for (unsigned i = 0; i < 12; i++)
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{
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sum += x_pow * two_div_pow / (factorial * factorial);
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factorial_mult += 1.0;
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x_pow *= x * x;
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two_div_pow *= 0.25;
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factorial *= factorial_mult;
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}
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return sum;
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}
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static void init_sinc_table(rarch_sinc_resampler_t *resamp)
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static inline double window_function(double index)
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{
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// Sinc phases: [..., p + 3, p + 2, p + 1, p + 0, p - 1, p - 2, p - 3, p - 4, ...]
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for (int i = 0; i < (1 << PHASE_BITS); i++)
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{
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for (int j = 0; j < TAPS; j++)
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{
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double p = (double)i / (1 << PHASE_BITS);
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double sinc_phase = M_PI * (p + (SIDELOBES - 1 - j));
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return besseli0(SINC_WINDOW_KAISER_BETA * sqrt(1 - index * index));
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}
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#else
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#error "No SINC window function defined."
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#endif
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float val = CUTOFF * sinc(CUTOFF * sinc_phase) * lanzcos(sinc_phase / SIDELOBES);
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resamp->phase_table[i][j] = val;
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static void init_sinc_table(rarch_sinc_resampler_t *resamp, double cutoff,
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float *phase_table, int phases, int taps)
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{
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double window_mod = window_function(0.0); // Need to normalize w(0) to 1.0.
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for (int i = 0; i < phases; i++)
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{
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for (int j = 0; j < taps; j++)
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{
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int n = j * phases + i;
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double window_phase = (double)n / (((1 << PHASE_BITS) * TAPS) - 1.0); // [0, 1].
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window_phase = 2.0 * window_phase - 1.0; // [-1, 1]
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double sinc_phase = SIDELOBES * window_phase;
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float val = cutoff * sinc(M_PI * sinc_phase * cutoff) * window_function(window_phase) / window_mod;
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phase_table[i * taps + j] = val;
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}
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}
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}
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@ -263,9 +330,9 @@ static void resampler_sinc_process(void *re_, struct resampler_data *data)
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{
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while (frames && re->time >= PHASES)
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{
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re->ptr = (re->ptr - 1) & (TAPS - 1);
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re->buffer_l[re->ptr + TAPS] = re->buffer_l[re->ptr] = *input++;
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re->buffer_r[re->ptr + TAPS] = re->buffer_r[re->ptr] = *input++;
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re->ptr = (re->ptr + 1) & (TAPS - 1);
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re->time -= PHASES;
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frames--;
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@ -296,7 +363,7 @@ static void *resampler_sinc_new(void)
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memset(re, 0, sizeof(*re));
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init_sinc_table(re);
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init_sinc_table(re, CUTOFF, &re->phase_table[0][0], 1 << PHASE_BITS, TAPS);
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#if defined(__AVX__) && ENABLE_AVX
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RARCH_LOG("Sinc resampler [AVX]\n");
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@ -1,4 +1,15 @@
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TESTS := test-hermite test-sinc test-snr-sinc test-snr-hermite
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TESTS := test-hermite \
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test-snr-hermite \
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test-sinc-lowest \
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test-snr-sinc-lowest \
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test-sinc-lower \
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test-snr-sinc-lower \
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test-sinc \
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test-snr-sinc \
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test-sinc-higher \
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test-snr-sinc-higher \
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test-sinc-highest \
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test-snr-sinc-highest
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CFLAGS += -O3 -g -Wall -pedantic -std=gnu99 -DRESAMPLER_TEST
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LDFLAGS += -lm
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@ -8,12 +19,6 @@ all: $(TESTS)
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test-hermite: ../hermite.o ../utils.o main.o resampler-hermite.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-sinc: ../sinc.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc: ../sinc.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-hermite: ../hermite.o ../utils.o snr.o resampler-hermite.o
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$(CC) -o $@ $^ $(LDFLAGS)
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@ -23,6 +28,51 @@ resampler-sinc.o: ../resampler.c
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resampler-hermite.o: ../resampler.c
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$(CC) -c -o $@ $< $(CFLAGS)
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sinc-lowest.o: ../sinc.c
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$(CC) -c -o $@ $< $(CFLAGS) -DHAVE_SINC -DSINC_LOWEST_QUALITY
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sinc-lower.o: ../sinc.c
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$(CC) -c -o $@ $< $(CFLAGS) -DHAVE_SINC -DSINC_LOWER_QUALITY
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sinc.o: ../sinc.c
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$(CC) -c -o $@ $< $(CFLAGS) -DHAVE_SINC
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sinc-higher.o: ../sinc.c
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$(CC) -c -o $@ $< $(CFLAGS) -DHAVE_SINC -DSINC_HIGHER_QUALITY
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sinc-highest.o: ../sinc.c
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$(CC) -c -o $@ $< $(CFLAGS) -DHAVE_SINC -DSINC_HIGHEST_QUALITY
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test-sinc-lowest: sinc-lowest.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc-lowest: sinc-lowest.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-sinc-lower: sinc-lower.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc-lower: sinc-lower.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-sinc: sinc.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc: sinc.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-sinc-higher: sinc-higher.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc-higher: sinc-higher.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-sinc-highest: sinc-highest.o ../utils.o main.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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test-snr-sinc-highest: sinc-highest.o ../utils.o snr.o ../hermite.o resampler-sinc.o
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$(CC) -o $@ $^ $(LDFLAGS)
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%.o: %.c
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$(CC) -c -o $@ $< $(CFLAGS)
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38
audio/test/sinc_test.m
Normal file
38
audio/test/sinc_test.m
Normal file
@ -0,0 +1,38 @@
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% MATLAB test case for RetroArch SINC upsampler.
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close all;
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% 4-tap and 8-tap are Lanczos windowed, but include here for completeness.
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sidelobes = [2 4 8 32 128];
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taps = sidelobes * 2;
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phases = 256;
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cutoffs = [0.65 0.75 0.825 0.90 0.95];
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betas = [2.0 3.0 5.5 10.5 14.5];
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freqs = 0.05 : 0.05 : 0.99;
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filters = length(taps);
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for i = 1 : filters
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filter_length = taps(i) * phases;
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% Generate SINC.
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sinc_indices = 2 * ((0 : (filter_length - 1)) / (filter_length - 1)) - 1;
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s = cutoffs(i) * sinc(cutoffs(i) * sinc_indices * sidelobes(i));
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win = kaiser(filter_length, betas(i))';
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filter = s .* win;
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impulse_response_half = 0.5 * upfirdn(1, filter, phases, phases / 2);
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figure('name', sprintf('Response SINC: %d taps', taps(i)));
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freqz(impulse_response_half);
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ylim([-200 0]);
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signal = zeros(1, 4001);
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for freq = freqs
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signal = signal + sin(pi * freq * (0 : 4000));
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end
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resampled = upfirdn(signal, filter, phases, round(phases * 44100 / 48000));
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figure('name', sprintf('Kaiser SINC: %d taps, w = %.f', taps(i), freq));
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freqz(resampled .* kaiser(length(resampled), 40.0)');
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ylim([-80 70]);
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end
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