revoice/dep/silk/src/SKP_Silk_find_LTP_FLP.c

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#include "SKP_Silk_main_FLP.h"
#include "SKP_Silk_tuning_parameters.h"

void SKP_Silk_find_LTP_FLP(
          SKP_float b[    NB_SUBFR * LTP_ORDER ],       /* O    LTP coefs                               */
          SKP_float WLTP[NB_SUBFR*LTP_ORDER*LTP_ORDER], /* O    Weight for LTP quantization             */
          SKP_float *LTPredCodGain,                     /* O    LTP coding gain                         */
    const SKP_float r_first[],                          /* I    LPC residual, signal + state for 10 ms  */
    const SKP_float r_last[],                           /* I    LPC residual, signal + state for 10 ms  */
    const SKP_int   lag[  NB_SUBFR ],                   /* I    LTP lags                                */
    const SKP_float Wght[ NB_SUBFR ],                   /* I    Weights                                 */
    const SKP_int   subfr_length,                       /* I    Subframe length                         */
    const SKP_int   mem_offset                          /* I    Number of samples in LTP memory         */
)
{
    SKP_int   i, k;
    SKP_float *b_ptr, temp, *WLTP_ptr;
    SKP_float LPC_res_nrg, LPC_LTP_res_nrg;
    SKP_float d[ NB_SUBFR ], m, g, delta_b[ LTP_ORDER ];
    SKP_float w[ NB_SUBFR ], nrg[ NB_SUBFR ], regu;
    SKP_float Rr[ LTP_ORDER ], rr[ NB_SUBFR ];
    const SKP_float *r_ptr, *lag_ptr;

    b_ptr    = b;
    WLTP_ptr = WLTP;
    r_ptr    = &r_first[ mem_offset ];
    for( k = 0; k < NB_SUBFR; k++ ) {
        if( k == ( NB_SUBFR >> 1 ) ) { /* Shift residual for last 10 ms */
            r_ptr = &r_last[ mem_offset ];
        }
        lag_ptr = r_ptr - ( lag[ k ] + LTP_ORDER / 2 );

        SKP_Silk_corrMatrix_FLP( lag_ptr, subfr_length, LTP_ORDER, WLTP_ptr );
        SKP_Silk_corrVector_FLP( lag_ptr, r_ptr, subfr_length, LTP_ORDER, Rr );

        rr[ k ] = ( SKP_float )SKP_Silk_energy_FLP( r_ptr, subfr_length );
        regu = 1.0f + rr[ k ] + 
            matrix_ptr( WLTP_ptr, 0, 0, LTP_ORDER ) + 
            matrix_ptr( WLTP_ptr, LTP_ORDER-1, LTP_ORDER-1, LTP_ORDER );
        regu *= LTP_DAMPING / 3;
        SKP_Silk_regularize_correlations_FLP( WLTP_ptr, &rr[ k ], regu, LTP_ORDER );
        SKP_Silk_solve_LDL_FLP( WLTP_ptr, LTP_ORDER, Rr, b_ptr );

        /* Calculate residual energy */
        nrg[ k ] = SKP_Silk_residual_energy_covar_FLP( b_ptr, WLTP_ptr, Rr, rr[ k ], LTP_ORDER );

        temp = Wght[ k ] / ( nrg[ k ] * Wght[ k ] + 0.01f * subfr_length );
        SKP_Silk_scale_vector_FLP( WLTP_ptr, temp, LTP_ORDER * LTP_ORDER );
        w[ k ] = matrix_ptr( WLTP_ptr, LTP_ORDER / 2, LTP_ORDER / 2, LTP_ORDER );
    
        r_ptr    += subfr_length;
        b_ptr    += LTP_ORDER;
        WLTP_ptr += LTP_ORDER * LTP_ORDER;
    }

    /* Compute LTP coding gain */
    if( LTPredCodGain != NULL ) {
        LPC_LTP_res_nrg = 1e-6f;
        LPC_res_nrg     = 0.0f;
        for( k = 0; k < NB_SUBFR; k++ ) {
            LPC_res_nrg     += rr[  k ] * Wght[ k ];
            LPC_LTP_res_nrg += nrg[ k ] * Wght[ k ];
        }
        
        SKP_assert( LPC_LTP_res_nrg > 0 );
        *LTPredCodGain = 3.0f * SKP_Silk_log2( LPC_res_nrg / LPC_LTP_res_nrg );
    }

    /* Smoothing */
    /* d = sum( B, 1 ); */
    b_ptr = b;
    for( k = 0; k < NB_SUBFR; k++ ) {
        d[ k ] = 0;
        for( i = 0; i < LTP_ORDER; i++ ) {
            d[ k ] += b_ptr[ i ];
        }
        b_ptr += LTP_ORDER;
    }
    /* m = ( w * d' ) / ( sum( w ) + 1e-3 ); */
    temp = 1e-3f;
    for( k = 0; k < NB_SUBFR; k++ ) {
        temp += w[ k ];
    }
    m = 0;
    for( k = 0; k < NB_SUBFR; k++ ) {
        m += d[ k ] * w[ k ];
    }
    m = m / temp;

    b_ptr = b;
    for( k = 0; k < NB_SUBFR; k++ ) {
        g = LTP_SMOOTHING / ( LTP_SMOOTHING + w[ k ] ) * ( m - d[ k ] );
        temp = 0;
        for( i = 0; i < LTP_ORDER; i++ ) {
            delta_b[ i ] = SKP_max_float( b_ptr[ i ], 0.1f );
            temp += delta_b[ i ];
        }
        temp = g / temp;
        for( i = 0; i < LTP_ORDER; i++ ) {
            b_ptr[ i ] = b_ptr[ i ] + delta_b[ i ] * temp;
        }
        b_ptr += LTP_ORDER;
    }
}