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     11 - Neither the name of Internet Society, IETF or IETF Trust, nor the
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     13 products derived from this software without specific prior written
     14 permission.
     15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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     18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
     19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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     23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     25 POSSIBILITY OF SUCH DAMAGE.
     26 ***********************************************************************/
     27 
     28 #ifdef HAVE_CONFIG_H
     29 #include "config.h"
     30 #endif
     31 
     32 #include "main_FIX.h"
     33 #include "stack_alloc.h"
     34 #include "tuning_parameters.h"
     35 
     36 /* Finds LPC vector from correlations, and converts to NLSF */
     37 void silk_find_LPC_FIX(
     38     silk_encoder_state              *psEncC,                                /* I/O  Encoder state                                                               */
     39     opus_int16                      NLSF_Q15[],                             /* O    NLSFs                                                                       */
     40     const opus_int16                x[],                                    /* I    Input signal                                                                */
     41     const opus_int32                minInvGain_Q30                          /* I    Inverse of max prediction gain                                              */
     42 )
     43 {
     44     opus_int     k, subfr_length;
     45     opus_int32   a_Q16[ MAX_LPC_ORDER ];
     46     opus_int     isInterpLower, shift;
     47     opus_int32   res_nrg0, res_nrg1;
     48     opus_int     rshift0, rshift1;
     49 
     50     /* Used only for LSF interpolation */
     51     opus_int32   a_tmp_Q16[ MAX_LPC_ORDER ], res_nrg_interp, res_nrg, res_tmp_nrg;
     52     opus_int     res_nrg_interp_Q, res_nrg_Q, res_tmp_nrg_Q;
     53     opus_int16   a_tmp_Q12[ MAX_LPC_ORDER ];
     54     opus_int16   NLSF0_Q15[ MAX_LPC_ORDER ];
     55     SAVE_STACK;
     56 
     57     subfr_length = psEncC->subfr_length + psEncC->predictLPCOrder;
     58 
     59     /* Default: no interpolation */
     60     psEncC->indices.NLSFInterpCoef_Q2 = 4;
     61 
     62     /* Burg AR analysis for the full frame */
     63     silk_burg_modified( &res_nrg, &res_nrg_Q, a_Q16, x, minInvGain_Q30, subfr_length, psEncC->nb_subfr, psEncC->predictLPCOrder, psEncC->arch );
     64 
     65     if( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) {
     66         VARDECL( opus_int16, LPC_res );
     67 
     68         /* Optimal solution for last 10 ms */
     69         silk_burg_modified( &res_tmp_nrg, &res_tmp_nrg_Q, a_tmp_Q16, x + 2 * subfr_length, minInvGain_Q30, subfr_length, 2, psEncC->predictLPCOrder, psEncC->arch );
     70 
     71         /* subtract residual energy here, as that's easier than adding it to the    */
     72         /* residual energy of the first 10 ms in each iteration of the search below */
     73         shift = res_tmp_nrg_Q - res_nrg_Q;
     74         if( shift >= 0 ) {
     75             if( shift < 32 ) {
     76                 res_nrg = res_nrg - silk_RSHIFT( res_tmp_nrg, shift );
     77             }
     78         } else {
     79             silk_assert( shift > -32 );
     80             res_nrg   = silk_RSHIFT( res_nrg, -shift ) - res_tmp_nrg;
     81             res_nrg_Q = res_tmp_nrg_Q;
     82         }
     83 
     84         /* Convert to NLSFs */
     85         silk_A2NLSF( NLSF_Q15, a_tmp_Q16, psEncC->predictLPCOrder );
     86 
     87         ALLOC( LPC_res, 2 * subfr_length, opus_int16 );
     88 
     89         /* Search over interpolation indices to find the one with lowest residual energy */
     90         for( k = 3; k >= 0; k-- ) {
     91             /* Interpolate NLSFs for first half */
     92             silk_interpolate( NLSF0_Q15, psEncC->prev_NLSFq_Q15, NLSF_Q15, k, psEncC->predictLPCOrder );
     93 
     94             /* Convert to LPC for residual energy evaluation */
     95             silk_NLSF2A( a_tmp_Q12, NLSF0_Q15, psEncC->predictLPCOrder );
     96 
     97             /* Calculate residual energy with NLSF interpolation */
     98             silk_LPC_analysis_filter( LPC_res, x, a_tmp_Q12, 2 * subfr_length, psEncC->predictLPCOrder, psEncC->arch );
     99 
    100             silk_sum_sqr_shift( &res_nrg0, &rshift0, LPC_res + psEncC->predictLPCOrder,                subfr_length - psEncC->predictLPCOrder );
    101             silk_sum_sqr_shift( &res_nrg1, &rshift1, LPC_res + psEncC->predictLPCOrder + subfr_length, subfr_length - psEncC->predictLPCOrder );
    102 
    103             /* Add subframe energies from first half frame */
    104             shift = rshift0 - rshift1;
    105             if( shift >= 0 ) {
    106                 res_nrg1         = silk_RSHIFT( res_nrg1, shift );
    107                 res_nrg_interp_Q = -rshift0;
    108             } else {
    109                 res_nrg0         = silk_RSHIFT( res_nrg0, -shift );
    110                 res_nrg_interp_Q = -rshift1;
    111             }
    112             res_nrg_interp = silk_ADD32( res_nrg0, res_nrg1 );
    113 
    114             /* Compare with first half energy without NLSF interpolation, or best interpolated value so far */
    115             shift = res_nrg_interp_Q - res_nrg_Q;
    116             if( shift >= 0 ) {
    117                 if( silk_RSHIFT( res_nrg_interp, shift ) < res_nrg ) {
    118                     isInterpLower = silk_TRUE;
    119                 } else {
    120                     isInterpLower = silk_FALSE;
    121                 }
    122             } else {
    123                 if( -shift < 32 ) {
    124                     if( res_nrg_interp < silk_RSHIFT( res_nrg, -shift ) ) {
    125                         isInterpLower = silk_TRUE;
    126                     } else {
    127                         isInterpLower = silk_FALSE;
    128                     }
    129                 } else {
    130                     isInterpLower = silk_FALSE;
    131                 }
    132             }
    133 
    134             /* Determine whether current interpolated NLSFs are best so far */
    135             if( isInterpLower == silk_TRUE ) {
    136                 /* Interpolation has lower residual energy */
    137                 res_nrg   = res_nrg_interp;
    138                 res_nrg_Q = res_nrg_interp_Q;
    139                 psEncC->indices.NLSFInterpCoef_Q2 = (opus_int8)k;
    140             }
    141         }
    142     }
    143 
    144     if( psEncC->indices.NLSFInterpCoef_Q2 == 4 ) {
    145         /* NLSF interpolation is currently inactive, calculate NLSFs from full frame AR coefficients */
    146         silk_A2NLSF( NLSF_Q15, a_Q16, psEncC->predictLPCOrder );
    147     }
    148 
    149     silk_assert( psEncC->indices.NLSFInterpCoef_Q2 == 4 || ( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) );
    150     RESTORE_STACK;
    151 }
    152