// file: $SPEECH_HOMEWORK4/hw4/class/snr_ratio/v1.0/snr_lp_2.cc
//

// isip include files
//
#include <string.h>
#include "signal_noise_ratio.h"
#include "signal_noise_ratio_constants.h"

// method: calculate_lp_spectrum_cc
//
// arguments:
//
// return: a logical_1 indicating status
//
logical_1 Signal::calculate_lp_spectrum_cc(float_4** lp_pred_a,
					   float_4**& lp_values_a,
					   int_4 samples_per_window_a,
					   float_4* lp_gain_a) {

  // loop over channels
  //
  for (int_4 i=0; i<num_chans_d; i++) {

    // loop over samples
    //
    for (int_4 j=0; j<samples_per_window_a; j++) {

      // declare useful variables
      //
      float_4 real = 1;
      float_4 imaginary = 0;

      // loop over coefficients
      //
      for (int_4 k=0; k<= lp_order_d; k++) {

	float_4 expn = (ISIP_TWOPI / samples_per_window_a) *
	  ((k * j) % samples_per_window_a);
	real -= lp_pred_a[i][k] * cos(expn);
	imaginary += lp_pred_a[i][k] * sin(expn);
	}
      
      lp_values_a[i][j] += sqrt(lp_gain_a[i] /
				(real * real + imaginary * imaginary));
    }
  }

  if (debug_level_d > 1) {
    for (int_4 i = 0; i < num_chans_d; i++) {
      for (int_4 j = 0; j < samples_per_window_a; j++) {
        fprintf(stdout, "chan %ld :: lp values [%ld] =  %.6f\n",
                i, j, lp_values_a[i][j]);
      }
    }
    fprintf(stdout, "\n");
  }

  // exit gracefully
  //
  return ISIP_TRUE;
  
}