freeswitch/libs/silk/src/SKP_Silk_CNG.c

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#include "SKP_Silk_main.h"

/* Generates excitation for CNG LPC synthesis */
SKP_INLINE void SKP_Silk_CNG_exc(
    SKP_int16                       residual[],         /* O    CNG residual signal Q0                      */
    SKP_int32                       exc_buf_Q10[],      /* I    Random samples buffer Q10                   */
    SKP_int32                       Gain_Q16,           /* I    Gain to apply                               */
    SKP_int                         length,             /* I    Length                                      */
    SKP_int32                       *rand_seed          /* I/O  Seed to random index generator              */
)
{
    SKP_int32 seed;
    SKP_int   i, idx, exc_mask;

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

    seed = *rand_seed;
    for( i = 0; i < length; i++ ) {
        seed = SKP_RAND( seed );
        idx = ( SKP_int )( SKP_RSHIFT( seed, 24 ) & exc_mask );
        SKP_assert( idx >= 0 );
        SKP_assert( idx <= CNG_BUF_MASK_MAX );
        residual[ i ] = ( SKP_int16 )SKP_SAT16( SKP_RSHIFT_ROUND( SKP_SMULWW( exc_buf_Q10[ idx ], Gain_Q16 ), 10 ) );
    }
    *rand_seed = seed;
}

void SKP_Silk_CNG_Reset(
    SKP_Silk_decoder_state      *psDec              /* I/O  Decoder state                               */
)
{
    SKP_int i, NLSF_step_Q15, NLSF_acc_Q15;

    NLSF_step_Q15 = SKP_DIV32_16( SKP_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 SKP_Silk_CNG(
    SKP_Silk_decoder_state      *psDec,             /* I/O  Decoder state                               */
    SKP_Silk_decoder_control    *psDecCtrl,         /* I/O  Decoder control                             */
    SKP_int16                   signal[],           /* I/O  Signal                                      */
    SKP_int                     length              /* I    Length of residual                          */
)
{
    SKP_int   i, subfr;
    SKP_int32 tmp_32, Gain_Q26, max_Gain_Q16;
    SKP_int16 LPC_buf[ MAX_LPC_ORDER ];
    SKP_int16 CNG_sig[ MAX_FRAME_LENGTH ];
    SKP_Silk_CNG_struct *psCNG;
    psCNG = &psDec->sCNG;

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

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

        /* Smoothing of LSF's  */
        for( i = 0; i < psDec->LPC_order; i++ ) {
            psCNG->CNG_smth_NLSF_Q15[ i ] += SKP_SMULWB( psDec->prevNLSF_Q15[ i ] - 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 < 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 */
        SKP_memmove( &psCNG->CNG_exc_buf_Q10[ psDec->subfr_length ], psCNG->CNG_exc_buf_Q10, ( NB_SUBFR - 1 ) * psDec->subfr_length * sizeof( SKP_int32 ) );
        SKP_memcpy(   psCNG->CNG_exc_buf_Q10, &psDec->exc_Q10[ subfr * psDec->subfr_length ], psDec->subfr_length * sizeof( SKP_int32 ) );

        /* Smooth gains */
        for( i = 0; i < NB_SUBFR; i++ ) {
            psCNG->CNG_smth_Gain_Q16 += SKP_SMULWB( psDecCtrl->Gains_Q16[ i ] - psCNG->CNG_smth_Gain_Q16, CNG_GAIN_SMTH_Q16 );
        }
    }

    /* Add CNG when packet is lost and / or when low speech activity */
    if( psDec->lossCnt ) {//|| psDec->vadFlag == NO_VOICE_ACTIVITY ) {

        /* Generate CNG excitation */
        SKP_Silk_CNG_exc( CNG_sig, psCNG->CNG_exc_buf_Q10,
                psCNG->CNG_smth_Gain_Q16, length, &psCNG->rand_seed );

        /* Convert CNG NLSF to filter representation */
        SKP_Silk_NLSF2A_stable( LPC_buf, psCNG->CNG_smth_NLSF_Q15, psDec->LPC_order );

        Gain_Q26 = ( SKP_int32 )1 << 26; /* 1.0 */

        /* Generate CNG signal, by synthesis filtering */
        if( psDec->LPC_order == 16 ) {
            SKP_Silk_LPC_synthesis_order16( CNG_sig, LPC_buf,
                Gain_Q26, psCNG->CNG_synth_state, CNG_sig, length );
        } else {
            SKP_Silk_LPC_synthesis_filter( CNG_sig, LPC_buf,
                Gain_Q26, psCNG->CNG_synth_state, CNG_sig, length, psDec->LPC_order );
        }
        /* Mix with signal */
        for( i = 0; i < length; i++ ) {
            tmp_32 = signal[ i ] + CNG_sig[ i ];
            signal[ i ] = SKP_SAT16( tmp_32 );
        }
    } else {
        SKP_memset( psCNG->CNG_synth_state, 0, psDec->LPC_order *  sizeof( SKP_int32 ) );
    }
}