/* Convert AR filter coefficients to NLSF parameters */
void silk_A2NLSF_FLP(
opus_int16 *NLSF_Q15, /* O NLSF vector [ LPC_order ] */
const silk_float *pAR, /* I LPC coefficients [ LPC_order ] */
const opus_int LPC_order /* I LPC order */
)
{
opus_int i;
opus_int32 a_fix_Q16[ MAX_LPC_ORDER ];
for( i = 0; i < LPC_order; i++ ) {
a_fix_Q16[ i ] = silk_float2int( pAR[ i ] * 65536.0f );
}
silk_A2NLSF( NLSF_Q15, a_fix_Q16, LPC_order );
}
/* Finds LPC vector from correlations, and converts to NLSF */
void silk_find_LPC_FIX(
silk_encoder_state *psEncC, /* I/O Encoder state */
opus_int16 NLSF_Q15[], /* O NLSFs */
const opus_int16 x[], /* I Input signal */
const opus_int32 minInvGain_Q30 /* I Inverse of max prediction gain */
)
{
opus_int k, subfr_length;
opus_int32 a_Q16[ MAX_LPC_ORDER ];
opus_int isInterpLower, shift;
opus_int32 res_nrg0, res_nrg1;
opus_int rshift0, rshift1;
/* Used only for LSF interpolation */
opus_int32 a_tmp_Q16[ MAX_LPC_ORDER ], res_nrg_interp, res_nrg, res_tmp_nrg;
opus_int res_nrg_interp_Q, res_nrg_Q, res_tmp_nrg_Q;
opus_int16 a_tmp_Q12[ MAX_LPC_ORDER ];
opus_int16 NLSF0_Q15[ MAX_LPC_ORDER ];
SAVE_STACK;
subfr_length = psEncC->subfr_length + psEncC->predictLPCOrder;
/* Default: no interpolation */
psEncC->indices.NLSFInterpCoef_Q2 = 4;
/* Burg AR analysis for the full frame */
silk_burg_modified( &res_nrg, &res_nrg_Q, a_Q16, x, minInvGain_Q30, subfr_length, psEncC->nb_subfr, psEncC->predictLPCOrder, psEncC->arch );
if( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) {
VARDECL( opus_int16, LPC_res );
/* Optimal solution for last 10 ms */
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 );
/* 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 */
shift = res_tmp_nrg_Q - res_nrg_Q;
if( shift >= 0 ) {
if( shift < 32 ) {
res_nrg = res_nrg - silk_RSHIFT( res_tmp_nrg, shift );
}
} else {
silk_assert( shift > -32 );
res_nrg = silk_RSHIFT( res_nrg, -shift ) - res_tmp_nrg;
res_nrg_Q = res_tmp_nrg_Q;
}
/* Convert to NLSFs */
silk_A2NLSF( NLSF_Q15, a_tmp_Q16, psEncC->predictLPCOrder );
ALLOC( LPC_res, 2 * subfr_length, opus_int16 );
/* Search over interpolation indices to find the one with lowest residual energy */
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( a_tmp_Q12, NLSF0_Q15, psEncC->predictLPCOrder );
/* Calculate residual energy with NLSF interpolation */
silk_LPC_analysis_filter( LPC_res, x, a_tmp_Q12, 2 * subfr_length, psEncC->predictLPCOrder );
silk_sum_sqr_shift( &res_nrg0, &rshift0, LPC_res + psEncC->predictLPCOrder, subfr_length - psEncC->predictLPCOrder );
silk_sum_sqr_shift( &res_nrg1, &rshift1, LPC_res + psEncC->predictLPCOrder + subfr_length, subfr_length - psEncC->predictLPCOrder );
/* Add subframe energies from first half frame */
shift = rshift0 - rshift1;
if( shift >= 0 ) {
res_nrg1 = silk_RSHIFT( res_nrg1, shift );
res_nrg_interp_Q = -rshift0;
} else {
res_nrg0 = silk_RSHIFT( res_nrg0, -shift );
res_nrg_interp_Q = -rshift1;
}
res_nrg_interp = silk_ADD32( res_nrg0, res_nrg1 );
/* Compare with first half energy without NLSF interpolation, or best interpolated value so far */
shift = res_nrg_interp_Q - res_nrg_Q;
if( shift >= 0 ) {
if( silk_RSHIFT( res_nrg_interp, shift ) < res_nrg ) {
isInterpLower = silk_TRUE;
} else {
isInterpLower = silk_FALSE;
}
} else {
if( -shift < 32 ) {
if( res_nrg_interp < silk_RSHIFT( res_nrg, -shift ) ) {
isInterpLower = silk_TRUE;
} else {
isInterpLower = silk_FALSE;
}
} else {
isInterpLower = silk_FALSE;
}
}
/* Determine whether current interpolated NLSFs are best so far */
if( isInterpLower == silk_TRUE ) {
/* Interpolation has lower residual energy */
res_nrg = res_nrg_interp;
res_nrg_Q = res_nrg_interp_Q;
psEncC->indices.NLSFInterpCoef_Q2 = (opus_int8)k;
}
}
}
if( psEncC->indices.NLSFInterpCoef_Q2 == 4 ) {
/* NLSF interpolation is currently inactive, calculate NLSFs from full frame AR coefficients */
silk_A2NLSF( NLSF_Q15, a_Q16, psEncC->predictLPCOrder );
}
silk_assert( psEncC->indices.NLSFInterpCoef_Q2 == 4 || ( psEncC->useInterpolatedNLSFs && !psEncC->first_frame_after_reset && psEncC->nb_subfr == MAX_NB_SUBFR ) );
RESTORE_STACK;
}
