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view libtwamr/residu.c @ 604:54f0f1b74c25

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libgsmhr1 TFO: require BFI=0 and SID=0 for homing In order for a received frame to be recognized as DHF, we need not only the correct bit pattern, but also BFI=0 and SID=0. The BFI=0 requirement should be obvious, while the SID=0 requirement is needed only for HR codec. With FR and EFR, SID classification comes from the payload bits and no separate check is needed - but in HR we get an out-of-band SID ternary flag. When SID=1, no payload bits are used at all; when SID=2, we use only the first 33 bits of the payload. Therefore, it is proper to conditionalize DHF acceptance on SID=0. We already implemented this logic in the just finished full decoder; now bring TFO code into agreement.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 04 Dec 2025 19:40:35 +0000
parents a2351f2ad4f8
children
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/*
********************************************************************************
*
*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
*                                R99   Version 3.3.0                
*                                REL-4 Version 4.1.0                
*
********************************************************************************
*
*      File             : residu.c
*      Purpose          : Computes the LP residual.
*      Description      : The LP residual is computed by filtering the input
*                       : speech through the LP inverse filter A(z).
*
********************************************************************************
*/
/*
********************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
********************************************************************************
*/
#include "namespace.h"
#include "residu.h"

/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "typedef.h"
#include "basic_op.h"
#include "no_count.h"
#include "cnst.h"

/*
********************************************************************************
*                         LOCAL VARIABLES AND TABLES
********************************************************************************
*/
/*
*--------------------------------------*
* Constants (defined in cnst.h         *
*--------------------------------------*
*  M         : LPC order               *
*--------------------------------------*
*/

/*
********************************************************************************
*                         PUBLIC PROGRAM CODE
********************************************************************************
*/
void Residu (
    Word16 a[], /* (i)     : prediction coefficients                      */
    Word16 x[], /* (i)     : speech signal                                */
    Word16 y[], /* (o)     : residual signal                              */
    Word16 lg   /* (i)     : size of filtering                            */
)
{
    Word16 i, j;
    Word32 s;

    for (i = 0; i < lg; i++)
    {
        s = L_mult (x[i], a[0]);
        for (j = 1; j <= M; j++)
        {
            s = L_mac (s, a[j], x[i - j]);
        }
        s = L_shl (s, 3);
        y[i] = round (s);       move16 (); 
    }
    return;
}