silk/NLSF_VQ.c

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

#include "main.h"

/* Compute quantization errors for an LPC_order element input vector for a VQ codebook */
void silk_NLSF_VQ(
    opus_int32                   err_Q26[],              /* O    Quantization errors [K]                     */
    const opus_int16             in_Q15[],               /* I    Input vectors to be quantized [LPC_order]   */
    const opus_uint8             pCB_Q8[],               /* I    Codebook vectors [K*LPC_order]              */
    const opus_int               K,                      /* I    Number of codebook vectors                  */
    const opus_int               LPC_order               /* I    Number of LPCs                              */
)
{
    opus_int        i, m;
    opus_int32      diff_Q15, sum_error_Q30, sum_error_Q26;

    silk_assert( LPC_order <= 16 );
    silk_assert( ( LPC_order & 1 ) == 0 );

    /* Loop over codebook */
    for( i = 0; i < K; i++ ) {
        sum_error_Q26 = 0;
        for( m = 0; m < LPC_order; m += 2 ) {
            /* Compute weighted squared quantization error for index m */
            diff_Q15 = silk_SUB_LSHIFT32( in_Q15[ m ], ( opus_int32 )*pCB_Q8++, 7 ); /* range: [ -32767 : 32767 ]*/
            sum_error_Q30 = silk_SMULBB( diff_Q15, diff_Q15 );

            /* Compute weighted squared quantization error for index m + 1 */
            diff_Q15 = silk_SUB_LSHIFT32( in_Q15[m + 1], ( opus_int32 )*pCB_Q8++, 7 ); /* range: [ -32767 : 32767 ]*/
            sum_error_Q30 = silk_SMLABB( sum_error_Q30, diff_Q15, diff_Q15 );

            sum_error_Q26 = silk_ADD_RSHIFT32( sum_error_Q26, sum_error_Q30, 4 );

            silk_assert( sum_error_Q26 >= 0 );
            silk_assert( sum_error_Q30 >= 0 );
        }
        err_Q26[ i ] = sum_error_Q26;
    }
}