// file: clpc_cal_7.cc
//
// this function computes the autocorrelation coefficients of a signal
//

// system include file
//
#include <stdio.h>

// local include file
//
#include "global_constants.h"
#include "calculate_lpc_constants.h"
#include "calculate_lpc.h"

// function: calculate_autocorr_cc
//
// arguments:
//    float**& autocorr_coeffs_a: (output) buffer contains the autocorrelation
//                                coefficients of the signal
//    float* signal_window_a: (input) buffer of signal
//    int samples_per_win_a: (input) number of samples per window
//    int num_chans_a: (input) number of channels
//    int lp_order_a: (input) type of window
//    int debug_mode_a: (input) debug level
//
// return: an int to indicate status
//
// this function calculates the autocorrelation coefficients of a signal using
// the equation:
//
//   r(k) = sum ( x(n) * x(n-k) ) n = 0 .. N-1 where
//
//   N is the number of samples in each channel and
//   k ranges from 0 - order of lpc
//
//
int calculate_autocorr_cc (float**& autocorr_coeffs_a, float* signal_window_a,
			   int samples_per_win_a, int num_chans_a,
			   int lp_order_a, int debug_mode_a) {

  // total number of autocorrelation coefficients for all channels
  //
  int autocorr_coeffs = lp_order_a + 1;

  // total number of samples for all channels
  //
  int num_samples = samples_per_win_a * num_chans_a;
  
  for (int chan = 0; chan < num_chans_a; chan++) {
    for (int coeff = 0; coeff < autocorr_coeffs; coeff++) {
      autocorr_coeffs_a[chan][coeff] = 0;
      for (int sample = chan; sample < (num_samples - coeff * num_chans_a);
	   sample += num_chans_a) {
	autocorr_coeffs_a[chan][coeff] += signal_window_a[sample] *
	  signal_window_a[sample + coeff * num_chans_a];
      }
    }
  }

  if (debug_mode_a > DEBUG_FULL) {
    for (int chan = 0; chan < num_chans_a; chan++) {
      for (int sample = 0; sample < autocorr_coeffs;
	   sample += num_chans_a) {
	fprintf(stdout, "chan %d :: autocorrelation coeff [%d] =  %.6f\n",
		chan, sample, autocorr_coeffs_a[chan][sample]);
      }
    }
    fprintf(stdout, "\n");
  }

  // exit gracefully
  //
  return TRUE;
}