CNG.c

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "main.h"
#include "stack_alloc.h"

/* Generates excitation for CNG LPC synthesis */
static OPUS_INLINE void silk_CNG_exc(
    opus_int32                       exc_Q14[],          /* O    CNG excitation signal Q10                   */
    opus_int32                       exc_buf_Q14[],      /* I    Random samples buffer Q10                   */
    opus_int                         length,             /* I    Length                                      */
    opus_int32                       *rand_seed          /* I/O  Seed to random index generator              */
)
{
    opus_int32 seed;
    opus_int   i, idx, exc_mask;

    exc_mask = CNG_BUF_MASK_MAX;
    while( exc_mask > length ) {
        exc_mask = silk_RSHIFT( exc_mask, 1 );
    }

    seed = *rand_seed;
    for( i = 0; i < length; i++ ) {
        seed = silk_RAND( seed );
        idx = (opus_int)( silk_RSHIFT( seed, 24 ) & exc_mask );
        silk_assert( idx >= 0 );
        silk_assert( idx <= CNG_BUF_MASK_MAX );
        exc_Q14[ i ] = exc_buf_Q14[ idx ];
    }
    *rand_seed = seed;
}

void silk_CNG_Reset(
    silk_decoder_state          *psDec                          /* I/O  Decoder state                               */
)
{
    opus_int i, NLSF_step_Q15, NLSF_acc_Q15;

    NLSF_step_Q15 = silk_DIV32_16( silk_int16_MAX, psDec->LPC_order + 1 );
    NLSF_acc_Q15 = 0;
    for( i = 0; i < psDec->LPC_order; i++ ) {
        NLSF_acc_Q15 += NLSF_step_Q15;
        psDec->sCNG.CNG_smth_NLSF_Q15[ i ] = NLSF_acc_Q15;
    }
    psDec->sCNG.CNG_smth_Gain_Q16 = 0;
    psDec->sCNG.rand_seed = 3176576;
}

/* Updates CNG estimate, and applies the CNG when packet was lost   */
void silk_CNG(
    silk_decoder_state          *psDec,                         /* I/O  Decoder state                               */
    silk_decoder_control        *psDecCtrl,                     /* I/O  Decoder control                             */
    opus_int16                  frame[],                        /* I/O  Signal                                      */
    opus_int                    length                          /* I    Length of residual                          */
)
{
    opus_int   i, subfr;
    opus_int32 LPC_pred_Q10, max_Gain_Q16, gain_Q16, gain_Q10;
    opus_int16 A_Q12[ MAX_LPC_ORDER ];
    silk_CNG_struct *psCNG = &psDec->sCNG;
    SAVE_STACK;

    if( psDec->fs_kHz != psCNG->fs_kHz ) {
        /* Reset state */
        silk_CNG_Reset( psDec );

        psCNG->fs_kHz = psDec->fs_kHz;
    }
    if( psDec->lossCnt == 0 && psDec->prevSignalType == TYPE_NO_VOICE_ACTIVITY ) {
        /* Update CNG parameters */

        /* Smoothing of LSF's  */
        for( i = 0; i < psDec->LPC_order; i++ ) {
            psCNG->CNG_smth_NLSF_Q15[ i ] += silk_SMULWB( (opus_int32)psDec->prevNLSF_Q15[ i ] - (opus_int32)psCNG->CNG_smth_NLSF_Q15[ i ], CNG_NLSF_SMTH_Q16 );
        }
        /* Find the subframe with the highest gain */
        max_Gain_Q16 = 0;
        subfr        = 0;
        for( i = 0; i < psDec->nb_subfr; i++ ) {
            if( psDecCtrl->Gains_Q16[ i ] > max_Gain_Q16 ) {
                max_Gain_Q16 = psDecCtrl->Gains_Q16[ i ];
                subfr        = i;
            }
        }
        /* Update CNG excitation buffer with excitation from this subframe */
        silk_memmove( &psCNG->CNG_exc_buf_Q14[ psDec->subfr_length ], psCNG->CNG_exc_buf_Q14, ( psDec->nb_subfr - 1 ) * psDec->subfr_length * sizeof( opus_int32 ) );
        silk_memcpy(   psCNG->CNG_exc_buf_Q14, &psDec->exc_Q14[ subfr * psDec->subfr_length ], psDec->subfr_length * sizeof( opus_int32 ) );

        /* Smooth gains */
        for( i = 0; i < psDec->nb_subfr; i++ ) {
            psCNG->CNG_smth_Gain_Q16 += silk_SMULWB( psDecCtrl->Gains_Q16[ i ] - psCNG->CNG_smth_Gain_Q16, CNG_GAIN_SMTH_Q16 );
            /* If the smoothed gain is 3 dB greater than this subframe's gain, use this subframe's gain to adapt faster. */
            if( silk_SMULWW( psCNG->CNG_smth_Gain_Q16, CNG_GAIN_SMTH_THRESHOLD_Q16 ) > psDecCtrl->Gains_Q16[ i ] ) {
                psCNG->CNG_smth_Gain_Q16 = psDecCtrl->Gains_Q16[ i ];
            }
        }
    }

    /* Add CNG when packet is lost or during DTX */
    if( psDec->lossCnt ) {
        VARDECL( opus_int32, CNG_sig_Q14 );
        ALLOC( CNG_sig_Q14, length + MAX_LPC_ORDER, opus_int32 );

        /* Generate CNG excitation */
        gain_Q16 = silk_SMULWW( psDec->sPLC.randScale_Q14, psDec->sPLC.prevGain_Q16[1] );
        if( gain_Q16 >= (1 << 21) || psCNG->CNG_smth_Gain_Q16 > (1 << 23) ) {
            gain_Q16 = silk_SMULTT( gain_Q16, gain_Q16 );
            gain_Q16 = silk_SUB_LSHIFT32(silk_SMULTT( psCNG->CNG_smth_Gain_Q16, psCNG->CNG_smth_Gain_Q16 ), gain_Q16, 5 );
            gain_Q16 = silk_LSHIFT32( silk_SQRT_APPROX( gain_Q16 ), 16 );
        } else {
            gain_Q16 = silk_SMULWW( gain_Q16, gain_Q16 );
            gain_Q16 = silk_SUB_LSHIFT32(silk_SMULWW( psCNG->CNG_smth_Gain_Q16, psCNG->CNG_smth_Gain_Q16 ), gain_Q16, 5 );
            gain_Q16 = silk_LSHIFT32( silk_SQRT_APPROX( gain_Q16 ), 8 );
        }
        gain_Q10 = silk_RSHIFT( gain_Q16, 6 );

        silk_CNG_exc( CNG_sig_Q14 + MAX_LPC_ORDER, psCNG->CNG_exc_buf_Q14, length, &psCNG->rand_seed );

        /* Convert CNG NLSF to filter representation */
        silk_NLSF2A( A_Q12, psCNG->CNG_smth_NLSF_Q15, psDec->LPC_order, psDec->arch );

        /* Generate CNG signal, by synthesis filtering */
        silk_memcpy( CNG_sig_Q14, psCNG->CNG_synth_state, MAX_LPC_ORDER * sizeof( opus_int32 ) );
        celt_assert( psDec->LPC_order == 10 || psDec->LPC_order == 16 );
        for( i = 0; i < length; i++ ) {
            /* Avoids introducing a bias because silk_SMLAWB() always rounds to -inf */
            LPC_pred_Q10 = silk_RSHIFT( psDec->LPC_order, 1 );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  1 ], A_Q12[ 0 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  2 ], A_Q12[ 1 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  3 ], A_Q12[ 2 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  4 ], A_Q12[ 3 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  5 ], A_Q12[ 4 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  6 ], A_Q12[ 5 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  7 ], A_Q12[ 6 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  8 ], A_Q12[ 7 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i -  9 ], A_Q12[ 8 ] );
            LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 10 ], A_Q12[ 9 ] );
            if( psDec->LPC_order == 16 ) {
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 11 ], A_Q12[ 10 ] );
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 12 ], A_Q12[ 11 ] );
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 13 ], A_Q12[ 12 ] );
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 14 ], A_Q12[ 13 ] );
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 15 ], A_Q12[ 14 ] );
                LPC_pred_Q10 = silk_SMLAWB( LPC_pred_Q10, CNG_sig_Q14[ MAX_LPC_ORDER + i - 16 ], A_Q12[ 15 ] );
            }

            /* Update states */
            CNG_sig_Q14[ MAX_LPC_ORDER + i ] = silk_ADD_SAT32( CNG_sig_Q14[ MAX_LPC_ORDER + i ], silk_LSHIFT_SAT32( LPC_pred_Q10, 4 ) );

            /* Scale with Gain and add to input signal */
            frame[ i ] = (opus_int16)silk_ADD_SAT16( frame[ i ], silk_SAT16( silk_RSHIFT_ROUND( silk_SMULWW( CNG_sig_Q14[ MAX_LPC_ORDER + i ], gain_Q10 ), 8 ) ) );

        }
        silk_memcpy( psCNG->CNG_synth_state, &CNG_sig_Q14[ length ], MAX_LPC_ORDER * sizeof( opus_int32 ) );
    } else {
        silk_memset( psCNG->CNG_synth_state, 0, psDec->LPC_order *  sizeof( opus_int32 ) );
    }
    RESTORE_STACK;
}