/* Interpolate two vectors */
void silk_interpolate(
opus_int16 xi[ MAX_LPC_ORDER ], /* O interpolated vector */
const opus_int16 x0[ MAX_LPC_ORDER ], /* I first vector */
const opus_int16 x1[ MAX_LPC_ORDER ], /* I second vector */
const opus_int ifact_Q2, /* I interp. factor, weight on 2nd vector */
const opus_int d /* I number of parameters */
)
{
opus_int i;
silk_assert( ifact_Q2 >= 0 );
silk_assert( ifact_Q2 <= 4 );
for( i = 0; i < d; i++ ) {
xi[ i ] = (opus_int16)silk_ADD_RSHIFT( x0[ i ], silk_SMULBB( x1[ i ] - x0[ i ], ifact_Q2 ), 2 );
}
}
/* Limit, stabilize, convert and quantize NLSFs */
void silk_process_NLSFs(
silk_encoder_state *psEncC, /* I/O Encoder state */
opus_int16 PredCoef_Q12[ 2 ][ MAX_LPC_ORDER ], /* O Prediction coefficients */
opus_int16 pNLSF_Q15[ MAX_LPC_ORDER ], /* I/O Normalized LSFs (quant out) (0 - (2^15-1)) */
const opus_int16 prev_NLSFq_Q15[ MAX_LPC_ORDER ] /* I Previous Normalized LSFs (0 - (2^15-1)) */
)
{
opus_int i, doInterpolate;
opus_int NLSF_mu_Q20;
opus_int32 i_sqr_Q15;
opus_int16 pNLSF0_temp_Q15[ MAX_LPC_ORDER ];
opus_int16 pNLSFW_QW[ MAX_LPC_ORDER ];
opus_int16 pNLSFW0_temp_QW[ MAX_LPC_ORDER ];
silk_assert(psEncC->speech_activity_Q8 >= 0);
silk_assert(psEncC->speech_activity_Q8 <= SILK_FIX_CONST(1.0, 8));
silk_assert(psEncC->useInterpolatedNLSFs == 1 || psEncC->indices.NLSFInterpCoef_Q2 == (1 << 2));
/***********************/
/* Calculate mu values */
/***********************/
/* NLSF_mu = 0.003 - 0.0015 * psEnc->speech_activity; */
NLSF_mu_Q20 = silk_SMLAWB(SILK_FIX_CONST(0.003, 20), SILK_FIX_CONST(-0.001, 28), psEncC->speech_activity_Q8);
if(psEncC->nb_subfr == 2) {
/* Multiply by 1.5 for 10 ms packets */
NLSF_mu_Q20 = silk_ADD_RSHIFT(NLSF_mu_Q20, NLSF_mu_Q20, 1);
}
silk_assert(NLSF_mu_Q20 > 0);
silk_assert(NLSF_mu_Q20 <= SILK_FIX_CONST(0.005, 20));
/* Calculate NLSF weights */
silk_NLSF_VQ_weights_laroia(pNLSFW_QW, pNLSF_Q15, psEncC->predictLPCOrder);
/* Update NLSF weights for interpolated NLSFs */
doInterpolate = (psEncC->useInterpolatedNLSFs == 1) && (psEncC->indices.NLSFInterpCoef_Q2 < 4);
if(doInterpolate) {
/* Calculate the interpolated NLSF vector for the first half */
silk_interpolate(pNLSF0_temp_Q15, prev_NLSFq_Q15, pNLSF_Q15,
psEncC->indices.NLSFInterpCoef_Q2, psEncC->predictLPCOrder);
/* Calculate first half NLSF weights for the interpolated NLSFs */
silk_NLSF_VQ_weights_laroia(pNLSFW0_temp_QW, pNLSF0_temp_Q15, psEncC->predictLPCOrder);
/* Update NLSF weights with contribution from first half */
i_sqr_Q15 = silk_LSHIFT(silk_SMULBB(psEncC->indices.NLSFInterpCoef_Q2, psEncC->indices.NLSFInterpCoef_Q2), 11);
for(i = 0; i < psEncC->predictLPCOrder; i++) {
pNLSFW_QW[ i ] = silk_SMLAWB(silk_RSHIFT(pNLSFW_QW[ i ], 1), (opus_int32)pNLSFW0_temp_QW[ i ], i_sqr_Q15);
silk_assert(pNLSFW_QW[ i ] >= 1);
}
}
silk_NLSF_encode(psEncC->indices.NLSFIndices, pNLSF_Q15, psEncC->psNLSF_CB, pNLSFW_QW,
NLSF_mu_Q20, psEncC->NLSF_MSVQ_Survivors, psEncC->indices.signalType);
/* Convert quantized NLSFs back to LPC coefficients */
silk_NLSF2A(PredCoef_Q12[ 1 ], pNLSF_Q15, psEncC->predictLPCOrder);
if(doInterpolate) {
/* Calculate the interpolated, quantized LSF vector for the first half */
silk_interpolate(pNLSF0_temp_Q15, prev_NLSFq_Q15, pNLSF_Q15,
psEncC->indices.NLSFInterpCoef_Q2, psEncC->predictLPCOrder);
/* Convert back to LPC coefficients */
silk_NLSF2A(PredCoef_Q12[ 0 ], pNLSF0_temp_Q15, psEncC->predictLPCOrder);
} else {
/* Copy LPC coefficients for first half from second half */
silk_memcpy(PredCoef_Q12[ 0 ], PredCoef_Q12[ 1 ], psEncC->predictLPCOrder * sizeof(opus_int16));
}
}
/* If not all roots are found, the a_Q16 coefficients are bandwidth expanded until convergence. */
void silk_A2NLSF(
opus_int16 *NLSF, /* O Normalized Line Spectral Frequencies in Q15 (0..2^15-1) [d] */
opus_int32 *a_Q16, /* I/O Monic whitening filter coefficients in Q16 [d] */
const opus_int d /* I Filter order (must be even) */
)
{
opus_int i, k, m, dd, root_ix, ffrac;
opus_int32 xlo, xhi, xmid;
opus_int32 ylo, yhi, ymid, thr;
opus_int32 nom, den;
opus_int32 P[ SILK_MAX_ORDER_LPC / 2 + 1 ];
opus_int32 Q[ SILK_MAX_ORDER_LPC / 2 + 1 ];
opus_int32 *PQ[ 2 ];
opus_int32 *p;
/* Store pointers to array */
PQ[ 0 ] = P;
PQ[ 1 ] = Q;
dd = silk_RSHIFT( d, 1 );
silk_A2NLSF_init( a_Q16, P, Q, dd );
/* Find roots, alternating between P and Q */
p = P; /* Pointer to polynomial */
xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/
ylo = silk_A2NLSF_eval_poly( p, xlo, dd );
if( ylo < 0 ) {
/* Set the first NLSF to zero and move on to the next */
NLSF[ 0 ] = 0;
p = Q; /* Pointer to polynomial */
ylo = silk_A2NLSF_eval_poly( p, xlo, dd );
root_ix = 1; /* Index of current root */
} else {
root_ix = 0; /* Index of current root */
}
k = 1; /* Loop counter */
i = 0; /* Counter for bandwidth expansions applied */
thr = 0;
while( 1 ) {
/* Evaluate polynomial */
xhi = silk_LSFCosTab_FIX_Q12[ k ]; /* Q12 */
yhi = silk_A2NLSF_eval_poly( p, xhi, dd );
/* Detect zero crossing */
if( ( ylo <= 0 && yhi >= thr ) || ( ylo >= 0 && yhi <= -thr ) ) {
if( yhi == 0 ) {
/* If the root lies exactly at the end of the current */
/* interval, look for the next root in the next interval */
thr = 1;
} else {
thr = 0;
}
/* Binary division */
ffrac = -256;
for( m = 0; m < BIN_DIV_STEPS_A2NLSF_FIX; m++ ) {
/* Evaluate polynomial */
xmid = silk_RSHIFT_ROUND( xlo + xhi, 1 );
ymid = silk_A2NLSF_eval_poly( p, xmid, dd );
/* Detect zero crossing */
if( ( ylo <= 0 && ymid >= 0 ) || ( ylo >= 0 && ymid <= 0 ) ) {
/* Reduce frequency */
xhi = xmid;
yhi = ymid;
} else {
/* Increase frequency */
xlo = xmid;
ylo = ymid;
ffrac = silk_ADD_RSHIFT( ffrac, 128, m );
}
}
/* Interpolate */
if( silk_abs( ylo ) < 65536 ) {
/* Avoid dividing by zero */
den = ylo - yhi;
nom = silk_LSHIFT( ylo, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) + silk_RSHIFT( den, 1 );
if( den != 0 ) {
ffrac += silk_DIV32( nom, den );
}
} else {
/* No risk of dividing by zero because abs(ylo - yhi) >= abs(ylo) >= 65536 */
ffrac += silk_DIV32( ylo, silk_RSHIFT( ylo - yhi, 8 - BIN_DIV_STEPS_A2NLSF_FIX ) );
}
NLSF[ root_ix ] = (opus_int16)silk_min_32( silk_LSHIFT( (opus_int32)k, 8 ) + ffrac, silk_int16_MAX );
silk_assert( NLSF[ root_ix ] >= 0 );
root_ix++; /* Next root */
if( root_ix >= d ) {
/* Found all roots */
break;
}
/* Alternate pointer to polynomial */
p = PQ[ root_ix & 1 ];
/* Evaluate polynomial */
xlo = silk_LSFCosTab_FIX_Q12[ k - 1 ]; /* Q12*/
ylo = silk_LSHIFT( 1 - ( root_ix & 2 ), 12 );
} else {
/* Increment loop counter */
k++;
xlo = xhi;
ylo = yhi;
thr = 0;
if( k > LSF_COS_TAB_SZ_FIX ) {
i++;
if( i > MAX_ITERATIONS_A2NLSF_FIX ) {
/* Set NLSFs to white spectrum and exit */
NLSF[ 0 ] = (opus_int16)silk_DIV32_16( 1 << 15, d + 1 );
for( k = 1; k < d; k++ ) {
NLSF[ k ] = (opus_int16)silk_SMULBB( k + 1, NLSF[ 0 ] );
}
return;
}
/* Error: Apply progressively more bandwidth expansion and run again */
silk_bwexpander_32( a_Q16, d, 65536 - silk_SMULBB( 10 + i, i ) ); /* 10_Q16 = 0.00015*/
silk_A2NLSF_init( a_Q16, P, Q, dd );
p = P; /* Pointer to polynomial */
xlo = silk_LSFCosTab_FIX_Q12[ 0 ]; /* Q12*/
ylo = silk_A2NLSF_eval_poly( p, xlo, dd );
if( ylo < 0 ) {
/* Set the first NLSF to zero and move on to the next */
NLSF[ 0 ] = 0;
p = Q; /* Pointer to polynomial */
ylo = silk_A2NLSF_eval_poly( p, xlo, dd );
root_ix = 1; /* Index of current root */
} else {
root_ix = 0; /* Index of current root */
}
k = 1; /* Reset loop counter */
}
}
}
}