ref: 9edde42690a11afea6681275411d2c5f16484ea4
dir: /silk/SKP_Silk_NLSF_decode.c/
/***********************************************************************
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***********************************************************************/
#include "SKP_Silk_main.h"
/* Predictive dequantizer for NLSF residuals */
void SKP_Silk_NLSF_residual_dequant( /* O Returns RD value in Q30 */
SKP_int16 x_Q10[], /* O Output [ order ] */
const SKP_int8 indices[], /* I Quantization indices [ order ] */
const SKP_uint8 pred_coef_Q8[], /* I Backward predictor coefs [ order ] */
const SKP_int quant_step_size_Q16, /* I Quantization step size */
const SKP_int16 order /* I Number of input values */
)
{
SKP_int i, out_Q10, pred_Q10;
out_Q10 = 0;
for( i = order-1; i >= 0; i-- ) {
pred_Q10 = SKP_RSHIFT( SKP_SMULBB( out_Q10, (SKP_int16)pred_coef_Q8[ i ] ), 8 );
out_Q10 = SKP_LSHIFT( indices[ i ], 10 );
if( out_Q10 > 0 ) {
out_Q10 = SKP_SUB16( out_Q10, SKP_FIX_CONST( NLSF_QUANT_LEVEL_ADJ, 10 ) );
} else if( out_Q10 < 0 ) {
out_Q10 = SKP_ADD16( out_Q10, SKP_FIX_CONST( NLSF_QUANT_LEVEL_ADJ, 10 ) );
}
out_Q10 = SKP_SMLAWB( pred_Q10, out_Q10, quant_step_size_Q16 );
x_Q10[ i ] = out_Q10;
}
}
/***********************/
/* NLSF vector decoder */
/***********************/
void SKP_Silk_NLSF_decode(
SKP_int16 *pNLSF_Q15, /* O Quantized NLSF vector [ LPC_ORDER ] */
SKP_int8 *NLSFIndices, /* I Codebook path vector [ LPC_ORDER + 1 ] */
const SKP_Silk_NLSF_CB_struct *psNLSF_CB /* I Codebook object */
)
{
SKP_int i;
SKP_uint8 pred_Q8[ MAX_LPC_ORDER ];
SKP_int16 ec_ix[ MAX_LPC_ORDER ];
SKP_int16 res_Q10[ MAX_LPC_ORDER ];
SKP_int16 W_tmp_Q5[ MAX_LPC_ORDER ];
SKP_int32 W_tmp_Q9;
const SKP_uint8 *pCB_element;
/* Decode first stage */
pCB_element = &psNLSF_CB->CB1_NLSF_Q8[ NLSFIndices[ 0 ] * psNLSF_CB->order ];
for( i = 0; i < psNLSF_CB->order; i++ ) {
pNLSF_Q15[ i ] = SKP_LSHIFT( ( SKP_int16 )pCB_element[ i ], 7 );
}
/* Unpack entropy table indices and predictor for current CB1 index */
SKP_Silk_NLSF_unpack( ec_ix, pred_Q8, psNLSF_CB, NLSFIndices[ 0 ] );
/* Trellis dequantizer */
SKP_Silk_NLSF_residual_dequant( res_Q10, &NLSFIndices[ 1 ], pred_Q8, psNLSF_CB->quantStepSize_Q16, psNLSF_CB->order );
/* Weights from codebook vector */
SKP_Silk_NLSF_VQ_weights_laroia( W_tmp_Q5, pNLSF_Q15, psNLSF_CB->order );
/* Apply inverse square-rooted weights and add to output */
for( i = 0; i < psNLSF_CB->order; i++ ) {
W_tmp_Q9 = SKP_Silk_SQRT_APPROX( SKP_LSHIFT( ( SKP_int32 )W_tmp_Q5[ i ], 13 ) );
pNLSF_Q15[ i ] = SKP_ADD16( pNLSF_Q15[ i ], (SKP_int16)SKP_DIV32_16( SKP_LSHIFT( ( SKP_int32 )res_Q10[ i ], 14 ), W_tmp_Q9 ) );
}
/* NLSF stabilization */
SKP_Silk_NLSF_stabilize( pNLSF_Q15, psNLSF_CB->deltaMin_Q15, psNLSF_CB->order );
}