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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 */
37void 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 );
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