// file: $ECE_8993/util/calculate_lpc/v1.0/clpc_comp_5.cc
//
// computes the autocorrelation 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_autocorrelation_cc
//
// arguments:
//
//  float_4* data: (input) a single channel of sampled data
//  float_4* autocor_coeffs: (output) autocorrelation coefficients
//  int_4 num_samples: (input) number of samples in the data stream
//  int_4 lp_order: (input) order of the lp model
//  
// return value: a logical_1 indicating status
//
// this function computes the autocorrelation coefficients of a signal
//
logical_1 compute_autocorrelation_cc(float_4* data_a,
				     float_4* autocor_coeffs_a,
				     int_4 num_samples_a, int_4 lp_order_a) {

  // find each autocorrelation coefficient
  //
  for (int_4 i = (int_4)0; i <= lp_order_a; i++) {

    // initialize the coefficient
    //
    autocor_coeffs_a[i] = (float_4)0.0;

    // loop over each sample in the data
    //
    for (int_4 k = (int_4)0; k < (num_samples_a - i); k++) {

      autocor_coeffs_a[i] += (data_a[k] * data_a[k+i]);
    }
  }
  
  // exit gracefully
  //
  return ISIP_TRUE;
}