yading@10: /*
yading@10:  * LPC utility code
yading@10:  * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: #include "libavutil/common.h"
yading@10: #include "libavutil/lls.h"
yading@10: 
yading@10: #define LPC_USE_DOUBLE
yading@10: #include "lpc.h"
yading@10: #include "libavutil/avassert.h"
yading@10: 
yading@10: 
yading@10: /**
yading@10:  * Apply Welch window function to audio block
yading@10:  */
yading@10: static void lpc_apply_welch_window_c(const int32_t *data, int len,
yading@10:                                      double *w_data)
yading@10: {
yading@10:     int i, n2;
yading@10:     double w;
yading@10:     double c;
yading@10: 
yading@10:     /* The optimization in commit fa4ed8c does not support odd len.
yading@10:      * If someone wants odd len extend that change. */
yading@10:     av_assert2(!(len & 1));
yading@10: 
yading@10:     n2 = (len >> 1);
yading@10:     c = 2.0 / (len - 1.0);
yading@10: 
yading@10:     w_data+=n2;
yading@10:       data+=n2;
yading@10:     for(i=0; i<n2; i++) {
yading@10:         w = c - n2 + i;
yading@10:         w = 1.0 - (w * w);
yading@10:         w_data[-i-1] = data[-i-1] * w;
yading@10:         w_data[+i  ] = data[+i  ] * w;
yading@10:     }
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Calculate autocorrelation data from audio samples
yading@10:  * A Welch window function is applied before calculation.
yading@10:  */
yading@10: static void lpc_compute_autocorr_c(const double *data, int len, int lag,
yading@10:                                    double *autoc)
yading@10: {
yading@10:     int i, j;
yading@10: 
yading@10:     for(j=0; j<lag; j+=2){
yading@10:         double sum0 = 1.0, sum1 = 1.0;
yading@10:         for(i=j; i<len; i++){
yading@10:             sum0 += data[i] * data[i-j];
yading@10:             sum1 += data[i] * data[i-j-1];
yading@10:         }
yading@10:         autoc[j  ] = sum0;
yading@10:         autoc[j+1] = sum1;
yading@10:     }
yading@10: 
yading@10:     if(j==lag){
yading@10:         double sum = 1.0;
yading@10:         for(i=j-1; i<len; i+=2){
yading@10:             sum += data[i  ] * data[i-j  ]
yading@10:                  + data[i+1] * data[i-j+1];
yading@10:         }
yading@10:         autoc[j] = sum;
yading@10:     }
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Quantize LPC coefficients
yading@10:  */
yading@10: static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
yading@10:                                int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
yading@10: {
yading@10:     int i;
yading@10:     double cmax, error;
yading@10:     int32_t qmax;
yading@10:     int sh;
yading@10: 
yading@10:     /* define maximum levels */
yading@10:     qmax = (1 << (precision - 1)) - 1;
yading@10: 
yading@10:     /* find maximum coefficient value */
yading@10:     cmax = 0.0;
yading@10:     for(i=0; i<order; i++) {
yading@10:         cmax= FFMAX(cmax, fabs(lpc_in[i]));
yading@10:     }
yading@10: 
yading@10:     /* if maximum value quantizes to zero, return all zeros */
yading@10:     if(cmax * (1 << max_shift) < 1.0) {
yading@10:         *shift = zero_shift;
yading@10:         memset(lpc_out, 0, sizeof(int32_t) * order);
yading@10:         return;
yading@10:     }
yading@10: 
yading@10:     /* calculate level shift which scales max coeff to available bits */
yading@10:     sh = max_shift;
yading@10:     while((cmax * (1 << sh) > qmax) && (sh > 0)) {
yading@10:         sh--;
yading@10:     }
yading@10: 
yading@10:     /* since negative shift values are unsupported in decoder, scale down
yading@10:        coefficients instead */
yading@10:     if(sh == 0 && cmax > qmax) {
yading@10:         double scale = ((double)qmax) / cmax;
yading@10:         for(i=0; i<order; i++) {
yading@10:             lpc_in[i] *= scale;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     /* output quantized coefficients and level shift */
yading@10:     error=0;
yading@10:     for(i=0; i<order; i++) {
yading@10:         error -= lpc_in[i] * (1 << sh);
yading@10:         lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
yading@10:         error -= lpc_out[i];
yading@10:     }
yading@10:     *shift = sh;
yading@10: }
yading@10: 
yading@10: static int estimate_best_order(double *ref, int min_order, int max_order)
yading@10: {
yading@10:     int i, est;
yading@10: 
yading@10:     est = min_order;
yading@10:     for(i=max_order-1; i>=min_order-1; i--) {
yading@10:         if(ref[i] > 0.10) {
yading@10:             est = i+1;
yading@10:             break;
yading@10:         }
yading@10:     }
yading@10:     return est;
yading@10: }
yading@10: 
yading@10: int ff_lpc_calc_ref_coefs(LPCContext *s,
yading@10:                           const int32_t *samples, int order, double *ref)
yading@10: {
yading@10:     double autoc[MAX_LPC_ORDER + 1];
yading@10: 
yading@10:     s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples);
yading@10:     s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
yading@10:     compute_ref_coefs(autoc, order, ref, NULL);
yading@10: 
yading@10:     return order;
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Calculate LPC coefficients for multiple orders
yading@10:  *
yading@10:  * @param lpc_type LPC method for determining coefficients,
yading@10:  *                 see #FFLPCType for details
yading@10:  */
yading@10: int ff_lpc_calc_coefs(LPCContext *s,
yading@10:                       const int32_t *samples, int blocksize, int min_order,
yading@10:                       int max_order, int precision,
yading@10:                       int32_t coefs[][MAX_LPC_ORDER], int *shift,
yading@10:                       enum FFLPCType lpc_type, int lpc_passes,
yading@10:                       int omethod, int max_shift, int zero_shift)
yading@10: {
yading@10:     double autoc[MAX_LPC_ORDER+1];
yading@10:     double ref[MAX_LPC_ORDER];
yading@10:     double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
yading@10:     int i, j, pass;
yading@10:     int opt_order;
yading@10: 
yading@10:     av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
yading@10:            lpc_type > FF_LPC_TYPE_FIXED);
yading@10: 
yading@10:     /* reinit LPC context if parameters have changed */
yading@10:     if (blocksize != s->blocksize || max_order != s->max_order ||
yading@10:         lpc_type  != s->lpc_type) {
yading@10:         ff_lpc_end(s);
yading@10:         ff_lpc_init(s, blocksize, max_order, lpc_type);
yading@10:     }
yading@10: 
yading@10:     if (lpc_type == FF_LPC_TYPE_LEVINSON) {
yading@10:         s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);
yading@10: 
yading@10:         s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
yading@10: 
yading@10:         compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
yading@10: 
yading@10:         for(i=0; i<max_order; i++)
yading@10:             ref[i] = fabs(lpc[i][i]);
yading@10:     } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
yading@10:         LLSModel m[2];
yading@10:         double var[MAX_LPC_ORDER+1], av_uninit(weight);
yading@10: 
yading@10:         if(lpc_passes <= 0)
yading@10:             lpc_passes = 2;
yading@10: 
yading@10:         for(pass=0; pass<lpc_passes; pass++){
yading@10:             avpriv_init_lls(&m[pass&1], max_order);
yading@10: 
yading@10:             weight=0;
yading@10:             for(i=max_order; i<blocksize; i++){
yading@10:                 for(j=0; j<=max_order; j++)
yading@10:                     var[j]= samples[i-j];
yading@10: 
yading@10:                 if(pass){
yading@10:                     double eval, inv, rinv;
yading@10:                     eval= avpriv_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
yading@10:                     eval= (512>>pass) + fabs(eval - var[0]);
yading@10:                     inv = 1/eval;
yading@10:                     rinv = sqrt(inv);
yading@10:                     for(j=0; j<=max_order; j++)
yading@10:                         var[j] *= rinv;
yading@10:                     weight += inv;
yading@10:                 }else
yading@10:                     weight++;
yading@10: 
yading@10:                 avpriv_update_lls(&m[pass&1], var, 1.0);
yading@10:             }
yading@10:             avpriv_solve_lls(&m[pass&1], 0.001, 0);
yading@10:         }
yading@10: 
yading@10:         for(i=0; i<max_order; i++){
yading@10:             for(j=0; j<max_order; j++)
yading@10:                 lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
yading@10:             ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
yading@10:         }
yading@10:         for(i=max_order-1; i>0; i--)
yading@10:             ref[i] = ref[i-1] - ref[i];
yading@10:     } else
yading@10:         av_assert0(0);
yading@10:     opt_order = max_order;
yading@10: 
yading@10:     if(omethod == ORDER_METHOD_EST) {
yading@10:         opt_order = estimate_best_order(ref, min_order, max_order);
yading@10:         i = opt_order-1;
yading@10:         quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
yading@10:     } else {
yading@10:         for(i=min_order-1; i<max_order; i++) {
yading@10:             quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     return opt_order;
yading@10: }
yading@10: 
yading@10: av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
yading@10:                         enum FFLPCType lpc_type)
yading@10: {
yading@10:     s->blocksize = blocksize;
yading@10:     s->max_order = max_order;
yading@10:     s->lpc_type  = lpc_type;
yading@10: 
yading@10:     if (lpc_type == FF_LPC_TYPE_LEVINSON) {
yading@10:         s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
yading@10:                                         sizeof(*s->windowed_samples));
yading@10:         if (!s->windowed_buffer)
yading@10:             return AVERROR(ENOMEM);
yading@10:         s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);
yading@10:     } else {
yading@10:         s->windowed_samples = NULL;
yading@10:     }
yading@10: 
yading@10:     s->lpc_apply_welch_window = lpc_apply_welch_window_c;
yading@10:     s->lpc_compute_autocorr   = lpc_compute_autocorr_c;
yading@10: 
yading@10:     if (ARCH_X86)
yading@10:         ff_lpc_init_x86(s);
yading@10: 
yading@10:     return 0;
yading@10: }
yading@10: 
yading@10: av_cold void ff_lpc_end(LPCContext *s)
yading@10: {
yading@10:     av_freep(&s->windowed_buffer);
yading@10: }