| /* | |
| * LPC utility code | |
| * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> | |
| * | |
| * This file is part of FFmpeg. | |
| * | |
| * FFmpeg is free software; you can redistribute it and/or | |
| * modify it under the terms of the GNU Lesser General Public | |
| * License as published by the Free Software Foundation; either | |
| * version 2.1 of the License, or (at your option) any later version. | |
| * | |
| * FFmpeg 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 | |
| * Lesser General Public License for more details. | |
| * | |
| * You should have received a copy of the GNU Lesser General Public | |
| * License along with FFmpeg; if not, write to the Free Software | |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
| */ | |
| #include "libavutil/common.h" | |
| #include "libavutil/lls.h" | |
| #include "libavutil/mem_internal.h" | |
| #define LPC_USE_DOUBLE | |
| #include "lpc.h" | |
| #include "lpc_functions.h" | |
| #include "libavutil/avassert.h" | |
| /** | |
| * Schur recursion. | |
| * Produces reflection coefficients from autocorrelation data. | |
| */ | |
| static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order, | |
| LPC_TYPE *ref, LPC_TYPE *error) | |
| { | |
| LPC_TYPE err; | |
| LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER]; | |
| for (int i = 0; i < max_order; i++) | |
| gen0[i] = gen1[i] = autoc[i + 1]; | |
| err = autoc[0]; | |
| ref[0] = -gen1[0] / ((LPC_USE_FIXED || err) ? err : 1); | |
| err += gen1[0] * ref[0]; | |
| if (error) | |
| error[0] = err; | |
| for (int i = 1; i < max_order; i++) { | |
| for (int j = 0; j < max_order - i; j++) { | |
| gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j]; | |
| gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j]; | |
| } | |
| ref[i] = -gen1[0] / ((LPC_USE_FIXED || err) ? err : 1); | |
| err += gen1[0] * ref[i]; | |
| if (error) | |
| error[i] = err; | |
| } | |
| } | |
| /** | |
| * Apply Welch window function to audio block | |
| */ | |
| static void lpc_apply_welch_window_c(const int32_t *data, ptrdiff_t len, | |
| double *w_data) | |
| { | |
| int i, n2; | |
| double w; | |
| double c; | |
| if (len == 1) { | |
| w_data[0] = 0.0; | |
| return; | |
| } | |
| n2 = (len >> 1); | |
| c = 2.0 / (len - 1.0); | |
| if (len & 1) { | |
| for(i=0; i<n2; i++) { | |
| w = c - i - 1.0; | |
| w = 1.0 - (w * w); | |
| w_data[i] = data[i] * w; | |
| w_data[len-1-i] = data[len-1-i] * w; | |
| } | |
| w_data[n2] = 0.0; | |
| return; | |
| } | |
| w_data+=n2; | |
| data+=n2; | |
| for(i=0; i<n2; i++) { | |
| w = c - n2 + i; | |
| w = 1.0 - (w * w); | |
| w_data[-i-1] = data[-i-1] * w; | |
| w_data[+i ] = data[+i ] * w; | |
| } | |
| } | |
| /** | |
| * Calculate autocorrelation data from audio samples | |
| * A Welch window function is applied before calculation. | |
| */ | |
| static void lpc_compute_autocorr_c(const double *data, ptrdiff_t len, int lag, | |
| double *autoc) | |
| { | |
| int i, j; | |
| for(j=0; j<lag; j+=2){ | |
| double sum0 = 1.0, sum1 = 1.0; | |
| for(i=j; i<len; i++){ | |
| sum0 += data[i] * data[i-j]; | |
| sum1 += data[i] * data[i-j-1]; | |
| } | |
| autoc[j ] = sum0; | |
| autoc[j+1] = sum1; | |
| } | |
| if(j==lag){ | |
| double sum = 1.0; | |
| for(i=j-1; i<len; i+=2){ | |
| sum += data[i ] * data[i-j ] | |
| + data[i+1] * data[i-j+1]; | |
| } | |
| autoc[j] = sum; | |
| } | |
| } | |
| /** | |
| * Quantize LPC coefficients | |
| */ | |
| static void quantize_lpc_coefs(double *lpc_in, int order, int precision, | |
| int32_t *lpc_out, int *shift, int min_shift, | |
| int max_shift, int zero_shift) | |
| { | |
| int i; | |
| double cmax, error; | |
| int32_t qmax; | |
| int sh; | |
| /* define maximum levels */ | |
| qmax = (1 << (precision - 1)) - 1; | |
| /* find maximum coefficient value */ | |
| cmax = 0.0; | |
| for(i=0; i<order; i++) { | |
| cmax= FFMAX(cmax, fabs(lpc_in[i])); | |
| } | |
| /* if maximum value quantizes to zero, return all zeros */ | |
| if(cmax * (1 << max_shift) < 1.0) { | |
| *shift = zero_shift; | |
| memset(lpc_out, 0, sizeof(int32_t) * order); | |
| return; | |
| } | |
| /* calculate level shift which scales max coeff to available bits */ | |
| sh = max_shift; | |
| while((cmax * (1 << sh) > qmax) && (sh > min_shift)) { | |
| sh--; | |
| } | |
| /* since negative shift values are unsupported in decoder, scale down | |
| coefficients instead */ | |
| if(sh == 0 && cmax > qmax) { | |
| double scale = ((double)qmax) / cmax; | |
| for(i=0; i<order; i++) { | |
| lpc_in[i] *= scale; | |
| } | |
| } | |
| /* output quantized coefficients and level shift */ | |
| error=0; | |
| for(i=0; i<order; i++) { | |
| error -= lpc_in[i] * (1 << sh); | |
| lpc_out[i] = av_clip(lrintf(error), -qmax, qmax); | |
| error -= lpc_out[i]; | |
| } | |
| *shift = sh; | |
| } | |
| static int estimate_best_order(double *ref, int min_order, int max_order) | |
| { | |
| int i, est; | |
| est = min_order; | |
| for(i=max_order-1; i>=min_order-1; i--) { | |
| if(ref[i] > 0.10) { | |
| est = i+1; | |
| break; | |
| } | |
| } | |
| return est; | |
| } | |
| int ff_lpc_calc_ref_coefs(LPCContext *s, | |
| const int32_t *samples, int order, double *ref) | |
| { | |
| double autoc[MAX_LPC_ORDER + 1]; | |
| s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples); | |
| s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc); | |
| compute_ref_coefs(autoc, order, ref, NULL); | |
| return order; | |
| } | |
| double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len, | |
| int order, double *ref) | |
| { | |
| int i; | |
| double signal = 0.0f, avg_err = 0.0f; | |
| double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER+1] = {0}; | |
| const double a = 0.5f, b = 1.0f - a; | |
| /* Apply windowing */ | |
| for (i = 0; i <= len / 2; i++) { | |
| double weight = a - b*cos((2*M_PI*i)/(len - 1)); | |
| s->windowed_samples[i] = weight*samples[i]; | |
| s->windowed_samples[len-1-i] = weight*samples[len-1-i]; | |
| } | |
| s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc); | |
| signal = autoc[0]; | |
| compute_ref_coefs(autoc, order, ref, error); | |
| for (i = 0; i < order; i++) | |
| avg_err = (avg_err + error[i])/2.0f; | |
| return avg_err ? signal/avg_err : NAN; | |
| } | |
| /** | |
| * Calculate LPC coefficients for multiple orders | |
| * | |
| * @param lpc_type LPC method for determining coefficients, | |
| * see #FFLPCType for details | |
| */ | |
| int ff_lpc_calc_coefs(LPCContext *s, | |
| const int32_t *samples, int blocksize, int min_order, | |
| int max_order, int precision, | |
| int32_t coefs[][MAX_LPC_ORDER], int *shift, | |
| enum FFLPCType lpc_type, int lpc_passes, | |
| int omethod, int min_shift, int max_shift, int zero_shift) | |
| { | |
| double autoc[MAX_LPC_ORDER+1]; | |
| double ref[MAX_LPC_ORDER] = { 0 }; | |
| double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER]; | |
| int i, j, pass = 0; | |
| int opt_order; | |
| av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && | |
| lpc_type > FF_LPC_TYPE_FIXED); | |
| av_assert0(lpc_type == FF_LPC_TYPE_CHOLESKY || lpc_type == FF_LPC_TYPE_LEVINSON); | |
| /* reinit LPC context if parameters have changed */ | |
| if (blocksize != s->blocksize || max_order != s->max_order || | |
| lpc_type != s->lpc_type) { | |
| ff_lpc_end(s); | |
| ff_lpc_init(s, blocksize, max_order, lpc_type); | |
| } | |
| if(lpc_passes <= 0) | |
| lpc_passes = 2; | |
| if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) { | |
| s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples); | |
| s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc); | |
| compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1); | |
| for(i=0; i<max_order; i++) | |
| ref[i] = fabs(lpc[i][i]); | |
| pass++; | |
| } | |
| if (lpc_type == FF_LPC_TYPE_CHOLESKY) { | |
| LLSModel *m = s->lls_models; | |
| LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]); | |
| double av_uninit(weight); | |
| memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var)); | |
| /* Avoids initializing with an unused value when lpc_passes == 1 */ | |
| if (lpc_passes > 1) | |
| for(j=0; j<max_order; j++) | |
| m[0].coeff[max_order-1][j] = -lpc[max_order-1][j]; | |
| for(; pass<lpc_passes; pass++){ | |
| avpriv_init_lls(&m[pass&1], max_order); | |
| weight=0; | |
| for(i=max_order; i<blocksize; i++){ | |
| for(j=0; j<=max_order; j++) | |
| var[j]= samples[i-j]; | |
| if(pass){ | |
| double eval, inv, rinv; | |
| eval= m[pass&1].evaluate_lls(&m[(pass-1)&1], var+1, max_order-1); | |
| eval= (512>>pass) + fabs(eval - var[0]); | |
| inv = 1/eval; | |
| rinv = sqrt(inv); | |
| for(j=0; j<=max_order; j++) | |
| var[j] *= rinv; | |
| weight += inv; | |
| }else | |
| weight++; | |
| m[pass&1].update_lls(&m[pass&1], var); | |
| } | |
| avpriv_solve_lls(&m[pass&1], 0.001, 0); | |
| } | |
| for(i=0; i<max_order; i++){ | |
| for(j=0; j<max_order; j++) | |
| lpc[i][j]=-m[(pass-1)&1].coeff[i][j]; | |
| ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000; | |
| } | |
| for(i=max_order-1; i>0; i--) | |
| ref[i] = ref[i-1] - ref[i]; | |
| } | |
| opt_order = max_order; | |
| if(omethod == ORDER_METHOD_EST) { | |
| opt_order = estimate_best_order(ref, min_order, max_order); | |
| i = opt_order-1; | |
| quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], | |
| min_shift, max_shift, zero_shift); | |
| } else { | |
| for(i=min_order-1; i<max_order; i++) { | |
| quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], | |
| min_shift, max_shift, zero_shift); | |
| } | |
| } | |
| return opt_order; | |
| } | |
| av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order, | |
| enum FFLPCType lpc_type) | |
| { | |
| s->blocksize = blocksize; | |
| s->max_order = max_order; | |
| s->lpc_type = lpc_type; | |
| s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) * | |
| sizeof(*s->windowed_samples)); | |
| if (!s->windowed_buffer) | |
| return AVERROR(ENOMEM); | |
| s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4); | |
| s->lpc_apply_welch_window = lpc_apply_welch_window_c; | |
| s->lpc_compute_autocorr = lpc_compute_autocorr_c; | |
| #if ARCH_RISCV | |
| ff_lpc_init_riscv(s); | |
| #elif ARCH_X86 | |
| ff_lpc_init_x86(s); | |
| #endif | |
| return 0; | |
| } | |
| av_cold void ff_lpc_end(LPCContext *s) | |
| { | |
| av_freep(&s->windowed_buffer); | |
| } |