/**
  * 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/lls.h"

 #define LPC_USE_DOUBLE
 #include "lpc.h"

 
 
 /**

  * Apply Welch window function to audio block
  */

 static void lpc_apply_welch_window_c(const int32_t *data, int len,
                                      double *w_data)

 {
     int i, n2;
     double w;
     double c;
 
     assert(!(len&1)); //the optimization in r11881 does not support odd len
                       //if someone wants odd len extend the change in r11881
 
     n2 = (len >> 1);
     c = 2.0 / (len - 1.0);
 
     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, int 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 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 > 0)) {
         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;
 }
 
 /**
  * Calculate LPC coefficients for multiple orders

  *
  * @param use_lpc LPC method for determining coefficients
  * 0  = LPC with fixed pre-defined coeffs
  * 1  = LPC with coeffs determined by Levinson-Durbin recursion
  * 2+ = LPC with coeffs determined by Cholesky factorization using (use_lpc-1) passes.

  */

 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 max_shift, int zero_shift)

 {
     double autoc[MAX_LPC_ORDER+1];
     double ref[MAX_LPC_ORDER];
     double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
     int i, j, pass;
     int opt_order;
 

     assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&

            lpc_type > FF_LPC_TYPE_FIXED);

     /* 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_type == FF_LPC_TYPE_LEVINSON) {

         double *windowed_samples = s->windowed_samples + max_order;
 
         s->lpc_apply_welch_window(samples, blocksize, windowed_samples);
 
         s->lpc_compute_autocorr(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]);

     } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {

         LLSModel m[2];

         double var[MAX_LPC_ORDER+1], av_uninit(weight);

         for(pass=0; pass<lpc_passes; pass++){

             av_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= av_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++;
 
                 av_update_lls(&m[pass&1], var, 1.0);
             }
             av_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], 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], 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;
 

     if (lpc_type == FF_LPC_TYPE_LEVINSON) {

         s->windowed_samples = av_mallocz((blocksize + max_order + 2) *
                                          sizeof(*s->windowed_samples));
         if (!s->windowed_samples)
             return AVERROR(ENOMEM);
     } else {
         s->windowed_samples = NULL;
     }
 

     s->lpc_apply_welch_window = lpc_apply_welch_window_c;
     s->lpc_compute_autocorr   = lpc_compute_autocorr_c;

 
     if (HAVE_MMX)
         ff_lpc_init_x86(s);

 
     return 0;
 }
 
 av_cold void ff_lpc_end(LPCContext *s)
 {
     av_freep(&s->windowed_samples);

 }