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 #ifdef HAVE_CONFIG_H

 #include "config.h"

 #endif

 #include "define.h"

 #include "main_FLP.h"

 #include "tuning_parameters.h"

 /* LPC analysis */

 void silk_find_LPC_FLP(

     silk_encoder_state              *psEncC,                            /* I/O  Encoder state                               */

     opus_int16                      NLSF_Q15[],                         /* O    NLSFs                                       */

     const silk_float                x[],                                /* I    Input signal                                */

     const silk_float                minInvGain                          /* I    Inverse of max prediction gain              */

 )

 {

     opus_int    k, subfr_length;

     silk_float  a[ MAX_LPC_ORDER ];

     /* Used only for NLSF interpolation */

     silk_float  res_nrg, res_nrg_2nd, res_nrg_interp;

     opus_int16  NLSF0_Q15[ MAX_LPC_ORDER ];

     silk_float  a_tmp[ MAX_LPC_ORDER ];

     silk_float  LPC_res[ MAX_FRAME_LENGTH + MAX_NB_SUBFR * MAX_LPC_ORDER ];

     subfr_length = psEncC->subfr_length + psEncC->predictLPCOrder;

     /* Default: No interpolation */

     psEncC->indices.NLSFInterpCoef_Q2 = 4;

     /* Burg AR analysis for the full frame */

     res_nrg = silk_burg_modified_FLP( a, x, minInvGain, subfr_length, psEncC->nb_subfr, psEncC->predictLPCOrder );

     if( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) {

         /* Optimal solution for last 10 ms; subtract residual energy here, as that's easier than        */

         /* adding it to the residual energy of the first 10 ms in each iteration of the search below    */

         res_nrg -= silk_burg_modified_FLP( a_tmp, x + ( MAX_NB_SUBFR / 2 ) * subfr_length, minInvGain, subfr_length, MAX_NB_SUBFR / 2, psEncC->predictLPCOrder );

         /* Convert to NLSFs */

         silk_A2NLSF_FLP( NLSF_Q15, a_tmp, psEncC->predictLPCOrder );

         /* Search over interpolation indices to find the one with lowest residual energy */

         res_nrg_2nd = silk_float_MAX;

         for( k = 3; k >= 0; k-- ) {

             /* Interpolate NLSFs for first half */

             silk_interpolate( NLSF0_Q15, psEncC->prev_NLSFq_Q15, NLSF_Q15, k, psEncC->predictLPCOrder );

             /* Convert to LPC for residual energy evaluation */

             silk_NLSF2A_FLP( a_tmp, NLSF0_Q15, psEncC->predictLPCOrder );

             /* Calculate residual energy with LSF interpolation */

             silk_LPC_analysis_filter_FLP( LPC_res, a_tmp, x, 2 * subfr_length, psEncC->predictLPCOrder );

             res_nrg_interp = (silk_float)(

                 silk_energy_FLP( LPC_res + psEncC->predictLPCOrder,                subfr_length - psEncC->predictLPCOrder ) +

                 silk_energy_FLP( LPC_res + psEncC->predictLPCOrder + subfr_length, subfr_length - psEncC->predictLPCOrder ) );

             /* Determine whether current interpolated NLSFs are best so far */

             if( res_nrg_interp < res_nrg ) {

                 /* Interpolation has lower residual energy */

                 res_nrg = res_nrg_interp;

                 psEncC->indices.NLSFInterpCoef_Q2 = (opus_int8)k;

             } else if( res_nrg_interp > res_nrg_2nd ) {

                 /* No reason to continue iterating - residual energies will continue to climb */

                 break;

             }

             res_nrg_2nd = res_nrg_interp;

         }

     }

     if( psEncC->indices.NLSFInterpCoef_Q2 == 4 ) {

         /* NLSF interpolation is currently inactive, calculate NLSFs from full frame AR coefficients */

         silk_A2NLSF_FLP( NLSF_Q15, a, psEncC->predictLPCOrder );

     }

     silk_assert( psEncC->indices.NLSFInterpCoef_Q2 == 4 || 

         ( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) );

 }