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/*                                                                      *
 * SKP_Silk_lowpass_int.c                                             *
 *                                                                      *
 * First order low-pass filter, with input as SKP_int32, running at     *
 * 48 kHz                                                               *
 *                                                                      *
 * Copyright 2006 (c), Skype Limited                                    *
 * Date: 060221                                                         *
 *                                                                      */
#include "SKP_Silk_SigProc_FIX.h"

/* First order low-pass filter, with input as SKP_int32, running at 48 kHz        */
void SKP_Silk_lowpass_int(
    const SKP_int32      *in,            /* I:    Q25 48 kHz signal; length = len */
    SKP_int32            *S,             /* I/O: Q25 state; length = 1            */
    SKP_int32            *out,           /* O:    Q25 48 kHz signal; length = len */
    const SKP_int32      len             /* I:    Number of samples               */
)
{
    SKP_int        k;
    SKP_int32    in_tmp, out_tmp, state;
    
    state = S[ 0 ];
    for( k = len; k > 0; k-- ) {    
        in_tmp  = *in++;
        in_tmp -= SKP_RSHIFT( in_tmp, 2 );              /* multiply by 0.75 */
        out_tmp = state + in_tmp;                       /* zero at nyquist  */
        state   = in_tmp - SKP_RSHIFT( out_tmp, 1 );    /* pole             */
        *out++  = out_tmp;
    }
    S[ 0 ] = state;
}


