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/**
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 * LPC utility code
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 * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "libavutil/lls.h"
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#define LPC_USE_DOUBLE
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#include "lpc.h"
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/**
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 * Apply Welch window function to audio block
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 */
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static void apply_welch_window_c(const int32_t *data, int len, double *w_data)
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{
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    int i, n2;
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    double w;
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    double c;
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    assert(!(len&1)); //the optimization in r11881 does not support odd len
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                      //if someone wants odd len extend the change in r11881
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    n2 = (len >> 1);
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    c = 2.0 / (len - 1.0);
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    w_data+=n2;
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      data+=n2;
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    for(i=0; i<n2; i++) {
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        w = c - n2 + i;
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        w = 1.0 - (w * w);
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        w_data[-i-1] = data[-i-1] * w;
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        w_data[+i  ] = data[+i  ] * w;
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    }
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}
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/**
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 * Calculate autocorrelation data from audio samples
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 * A Welch window function is applied before calculation.
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 */
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static void lpc_compute_autocorr_c(const double *data, int len, int lag,
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                             double *autoc)
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{
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    int i, j;
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    for(j=0; j<lag; j+=2){
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        double sum0 = 1.0, sum1 = 1.0;
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        for(i=j; i<len; i++){
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            sum0 += data[i] * data[i-j];
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            sum1 += data[i] * data[i-j-1];
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        }
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        autoc[j  ] = sum0;
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        autoc[j+1] = sum1;
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    }
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    if(j==lag){
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        double sum = 1.0;
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        for(i=j-1; i<len; i+=2){
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            sum += data[i  ] * data[i-j  ]
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                 + data[i+1] * data[i-j+1];
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        }
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        autoc[j] = sum;
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    }
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}
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/**
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 * Quantize LPC coefficients
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 */
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static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
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                               int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
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{
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    int i;
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    double cmax, error;
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    int32_t qmax;
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    int sh;
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    /* define maximum levels */
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    qmax = (1 << (precision - 1)) - 1;
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    /* find maximum coefficient value */
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    cmax = 0.0;
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    for(i=0; i<order; i++) {
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        cmax= FFMAX(cmax, fabs(lpc_in[i]));
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    }
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    /* if maximum value quantizes to zero, return all zeros */
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    if(cmax * (1 << max_shift) < 1.0) {
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        *shift = zero_shift;
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        memset(lpc_out, 0, sizeof(int32_t) * order);
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        return;
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    }
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    /* calculate level shift which scales max coeff to available bits */
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    sh = max_shift;
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    while((cmax * (1 << sh) > qmax) && (sh > 0)) {
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        sh--;
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    }
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    /* since negative shift values are unsupported in decoder, scale down
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       coefficients instead */
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    if(sh == 0 && cmax > qmax) {
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        double scale = ((double)qmax) / cmax;
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        for(i=0; i<order; i++) {
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            lpc_in[i] *= scale;
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        }
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    }
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    /* output quantized coefficients and level shift */
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    error=0;
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    for(i=0; i<order; i++) {
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        error -= lpc_in[i] * (1 << sh);
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        lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
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        error -= lpc_out[i];
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    }
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    *shift = sh;
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}
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static int estimate_best_order(double *ref, int min_order, int max_order)
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{
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    int i, est;
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    est = min_order;
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    for(i=max_order-1; i>=min_order-1; i--) {
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        if(ref[i] > 0.10) {
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            est = i+1;
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            break;
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        }
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    }
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    return est;
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}
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/**
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 * Calculate LPC coefficients for multiple orders
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 *
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 * @param use_lpc LPC method for determining coefficients
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 * 0  = LPC with fixed pre-defined coeffs
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 * 1  = LPC with coeffs determined by Levinson-Durbin recursion
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 * 2+ = LPC with coeffs determined by Cholesky factorization using (use_lpc-1) passes.
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 */
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int ff_lpc_calc_coefs(LPCContext *s,
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                      const int32_t *samples, int blocksize, int min_order,
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                      int max_order, int precision,
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                      int32_t coefs[][MAX_LPC_ORDER], int *shift,
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                      enum AVLPCType lpc_type, int lpc_passes,
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                      int omethod, int max_shift, int zero_shift)
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{
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    double autoc[MAX_LPC_ORDER+1];
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    double ref[MAX_LPC_ORDER];
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    double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
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    int i, j, pass;
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    int opt_order;
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    assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
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           lpc_type > AV_LPC_TYPE_FIXED);
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    /* reinit LPC context if parameters have changed */
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    if (blocksize != s->blocksize || max_order != s->max_order ||
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        lpc_type  != s->lpc_type) {
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        ff_lpc_end(s);
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        ff_lpc_init(s, blocksize, max_order, lpc_type);
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    }
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    if (lpc_type == AV_LPC_TYPE_LEVINSON) {
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        double *windowed_samples = s->windowed_samples + max_order;
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        s->lpc_apply_welch_window(samples, blocksize, windowed_samples);
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        s->lpc_compute_autocorr(windowed_samples, blocksize, max_order, autoc);
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        compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
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        for(i=0; i<max_order; i++)
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            ref[i] = fabs(lpc[i][i]);
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    } else if (lpc_type == AV_LPC_TYPE_CHOLESKY) {
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        LLSModel m[2];
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        double var[MAX_LPC_ORDER+1], av_uninit(weight);
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        for(pass=0; pass<lpc_passes; pass++){
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            av_init_lls(&m[pass&1], max_order);
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            weight=0;
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            for(i=max_order; i<blocksize; i++){
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                for(j=0; j<=max_order; j++)
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                    var[j]= samples[i-j];
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                if(pass){
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                    double eval, inv, rinv;
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                    eval= av_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
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                    eval= (512>>pass) + fabs(eval - var[0]);
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                    inv = 1/eval;
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                    rinv = sqrt(inv);
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                    for(j=0; j<=max_order; j++)
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                        var[j] *= rinv;
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                    weight += inv;
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                }else
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                    weight++;
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                av_update_lls(&m[pass&1], var, 1.0);
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            }
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            av_solve_lls(&m[pass&1], 0.001, 0);
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        }
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        for(i=0; i<max_order; i++){
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            for(j=0; j<max_order; j++)
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                lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
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            ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
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        }
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        for(i=max_order-1; i>0; i--)
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            ref[i] = ref[i-1] - ref[i];
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    }
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    opt_order = max_order;
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    if(omethod == ORDER_METHOD_EST) {
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        opt_order = estimate_best_order(ref, min_order, max_order);
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        i = opt_order-1;
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        quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
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    } else {
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        for(i=min_order-1; i<max_order; i++) {
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            quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
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        }
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    }
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    return opt_order;
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}
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av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
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                        enum AVLPCType lpc_type)
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{
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    s->blocksize = blocksize;
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    s->max_order = max_order;
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    s->lpc_type  = lpc_type;
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    if (lpc_type == AV_LPC_TYPE_LEVINSON) {
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        s->windowed_samples = av_mallocz((blocksize + max_order + 2) *
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                                         sizeof(*s->windowed_samples));
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        if (!s->windowed_samples)
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            return AVERROR(ENOMEM);
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    } else {
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        s->windowed_samples = NULL;
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    }
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    s->lpc_apply_welch_window = apply_welch_window_c;
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    s->lpc_compute_autocorr = lpc_compute_autocorr_c;
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    if (HAVE_MMX)
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        ff_lpc_init_x86(s);
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    return 0;
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}
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av_cold void ff_lpc_end(LPCContext *s)
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{
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    av_freep(&s->windowed_samples);
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}