/*

  * 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"

 #define LPC_USE_DOUBLE
 #include "lpc.h"

 #include "libavutil/avassert.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;
 
     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;
         }
         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, 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 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 signal/avg_err;
 }
 

 /**
  * 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));

         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_X86)

         ff_lpc_init_x86(s);

 
     return 0;
 }
 
 av_cold void ff_lpc_end(LPCContext *s)
 {

     av_freep(&s->windowed_buffer);

 }