freeswitch/libs/silk/src/SKP_Silk_residual_energy_FIX.c

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#include "SKP_Silk_main_FIX.h"

/* Calculates residual energies of input subframes where all subframes have LPC_order   */
/* of preceeding samples                                                                */
void SKP_Silk_residual_energy_FIX(
          SKP_int32 nrgs[ NB_SUBFR ],           /* O    Residual energy per subframe    */
          SKP_int   nrgsQ[ NB_SUBFR ],          /* O    Q value per subframe            */
    const SKP_int16 x[],                        /* I    Input signal                    */
          SKP_int16 a_Q12[ 2 ][ MAX_LPC_ORDER ],/* I    AR coefs for each frame half    */
    const SKP_int32 gains[ NB_SUBFR ],          /* I    Quantization gains              */
    const SKP_int   subfr_length,               /* I    Subframe length                 */
    const SKP_int   LPC_order                   /* I    LPC order                       */
)
{
    SKP_int         offset, i, j, rshift, lz1, lz2;
    SKP_int16       *LPC_res_ptr, LPC_res[ ( MAX_FRAME_LENGTH + NB_SUBFR * MAX_LPC_ORDER ) / 2 ];
    const SKP_int16 *x_ptr;
    SKP_int16       S[ MAX_LPC_ORDER ];
    SKP_int32       tmp32;

    x_ptr  = x;
    offset = LPC_order + subfr_length;

    /* Filter input to create the LPC residual for each frame half, and measure subframe energies */
    for( i = 0; i < 2; i++ ) {
        /* Calculate half frame LPC residual signal including preceeding samples */
        SKP_memset( S, 0, LPC_order * sizeof( SKP_int16 ) );
        SKP_Silk_LPC_analysis_filter( x_ptr, a_Q12[ i ], S, LPC_res, ( NB_SUBFR >> 1 ) * offset, LPC_order );

        /* Point to first subframe of the just calculated LPC residual signal */
        LPC_res_ptr = LPC_res + LPC_order;
        for( j = 0; j < ( NB_SUBFR >> 1 ); j++ ) {
            /* Measure subframe energy */
            SKP_Silk_sum_sqr_shift( &nrgs[ i * ( NB_SUBFR >> 1 ) + j ], &rshift, LPC_res_ptr, subfr_length );

            /* Set Q values for the measured energy */
            nrgsQ[ i * ( NB_SUBFR >> 1 ) + j ] = -rshift;

            /* Move to next subframe */
            LPC_res_ptr += offset;
        }
        /* Move to next frame half */
        x_ptr += ( NB_SUBFR >> 1 ) * offset;
    }

    /* Apply the squared subframe gains */
    for( i = 0; i < NB_SUBFR; i++ ) {
        /* Fully upscale gains and energies */
        lz1 = SKP_Silk_CLZ32( nrgs[  i ] ) - 1;
        lz2 = SKP_Silk_CLZ32( gains[ i ] ) - 1;

        tmp32 = SKP_LSHIFT32( gains[ i ], lz2 );

        /* Find squared gains */
        tmp32 = SKP_SMMUL( tmp32, tmp32 ); // Q( 2 * lz2 - 32 )

        /* Scale energies */
        nrgs[ i ] = SKP_SMMUL( tmp32, SKP_LSHIFT32( nrgs[ i ], lz1 ) ); // Q( nrgsQ[ i ] + lz1 + 2 * lz2 - 32 - 32 )
        nrgsQ[ i ] += lz1 + 2 * lz2 - 32 - 32;
    }
}