// file: clpc_cal_9.cc
//
// this function calculates the spectrum of the signal given the lp
// coefficients
//

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

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

// function: calculate_spect_cc
//
// arguments:
//    float**& lp_spect_coeffs_a: (output) spectrum of a signal
//    float** pred_coeffs_a: (input) buffer contains the prediction 
//                            coefficients of the signal
//    float* lp_gain_a: (output) predictor gain
//    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 spectrum of a signal using the coefficients
//
//
int calculate_spect_cc (float**& lp_spect_coeffs_a, float** pred_coeffs_a,
			float* lp_gain_a, int samples_per_win_a,
			int num_chans_a, int lp_order_a, int debug_mode_a) {
  
  for (int chan = 0; chan < num_chans_a; chan++) {
    
    for (int sample = 0; sample < samples_per_win_a; sample++) {
      
      float factor_rl = 1;
      float factor_img = 0;

      for (int coeff = 0; coeff <= lp_order_a; coeff++) {
	
	float expn = (2 * M_PI / samples_per_win_a) *
	  ((coeff * sample) % samples_per_win_a);
	factor_rl -= pred_coeffs_a[chan][coeff] * cos(expn);
	factor_img += pred_coeffs_a[chan][coeff] * sin(expn);
      }
      lp_spect_coeffs_a[chan][sample] += sqrt(lp_gain_a[chan] /
		      (factor_rl * factor_rl + factor_img * factor_img));
    }
  }
  
  if (debug_mode_a > DEBUG_FULL) {
    
    for (int chan = 0; chan < num_chans_a; chan++) {
      for (int coeff = 0; coeff <= lp_order_a; coeff++) {
	fprintf(stdout, "chan %d :: lp coeff [%d] =  %.6f\n",
		chan, coeff, lp_spect_coeffs_a[chan][coeff]);
      }
    }
    fprintf(stdout, "\n");
  }

  // exit gracefully
  //
  return TRUE;
}