// file: $SPEECH_HOMEWORK4/hw4/class/snr_ratio/v1.0/snr_dft_0.cc
//

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

// method: perform_dft_cc
//
// arguments:
//  float_4* buffer (input/output) signal to perform hamming window on
//  int_4 samples_per_window (input) the number of samples in one window
//
// return: a logical_1 indicating status
//
logical_1 Signal::perform_dft_cc(float_4* buffer_a, float_4**& dft_values_a,
				 int_4 samples_per_window_a) {

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

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

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

      for (int_4 k=0; k<samples_per_window_a; k++) {

	// get x(n)
	//
	float_4 n = buffer_a[k*num_chans_d+i];
      
	// calculate the real and imaginary parts of the dft
	//
	float_4 expn = ISIP_TWOPI * k * j / samples_per_window_a;
	real += n * cos(expn);
	imaginary -= n * sin(expn);
      }

      // store the value
      //
      dft_values_a[i][j] = sqrt((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 :: dft values [%ld] =  %.6f\n",
		i, j, dft_values_a[i][j*num_chans_d+i]);
      }
    }
    fprintf(stdout, "\n");
  }
  
  // exit gracefully
  //
  return ISIP_TRUE;
  
}