// file: $ECE_8993/util/calculate_lpc/v1.0/clpc_comp_2.cc
//
// computes the magnitude dft coefficients of the input data
//

// isip include files
//
#include <integral.h>
#include <integral_constants.h>

// local include files
//
#include "calculate_lpc.h"

#include "calculate_lpc_constants.h"

// function: compute_dft_cc
//
// arguments:
//
//  float_4* data: (input) a single channel of sampled data
//  float_4* dft_data: (output) magnitude of the dft coefficients
//  int_4 num_samples: (input) number of samples in the data stream
//  
// return value: a logical_1 indicating status
//
// this function computes the dft of the input data and stores the
// magnitude coefficients in the dft_data array
//
logical_1 compute_dft_cc(float_4* data_a, float_4* dft_data_a,
			 int_4 num_samples_a) {

  // loop over all frequency bins
  //
  for (int_4 k = (int_4)0; k < num_samples_a; k++) {

    // declare local accumulators
    //
    float_4 sumr = (float_4)0.0;
    float_4 sumi = (float_4)0.0;

    // loop over all time samples
    //
    for (int_4 n = (int_4)0; n < num_samples_a; n++) {

      // compute the argument
      //
      float_4 arg = ISIP_TWOPI * (float_4)n * (float_4)k /
	(float_4)num_samples_a;

      // compute the real part
      //
      sumr += data_a[n] * cos(arg);

      // compute the imaginary part
      //
      sumi += -data_a[n] * sin(arg);
    }

    // store the frequency value in magnitude form
    //
    dft_data_a[k] = sqrt((sumr * sumr) + (sumi * sumi));
  }

  // exit gracefully
  //
  return ISIP_TRUE;
}