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view libtwamr/sid_sync.c @ 605:63f774192906

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gsmhr_decoder_twts002_in(): set BFI=1 SID=1 for invalid SID When a received TW-TS-002 RTP payload indicates invalid SID, which of the 3 possible BFI/SID combinations should we pass to our internal ETSI-based speech decoder or TFO engine? Our original code passed BFI=0 SID=1, but upon further reflection, BFI=1 SID=1 is a better choice. In the corner case where received invalid SID is fed to a full decoder in homed state, setting BFI=1 allows that decoder to emit zeros on PCM and stay homed, instead of launching into full decoding.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 04 Dec 2025 21:01:46 +0000
parents a8b73b1c5b19
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             : sid_sync.c
*
*****************************************************************************
*/
/*
*****************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
*****************************************************************************
*/
#include "namespace.h"
#include "sid_sync.h"
 
/*
*****************************************************************************
*                         INCLUDE FILES
*****************************************************************************
*/
#include "tw_amr.h"
#include "typedef.h"
#include "basic_op.h"
#include "no_count.h"

/*
*****************************************************************************
*                         LOCAL VARIABLES AND TABLES
*****************************************************************************
*/

/*
*****************************************************************************
*                         PUBLIC PROGRAM CODE
*****************************************************************************
*/

void sid_sync_reset (sid_syncState *st)
{
    st->sid_update_rate = 8;
    st->sid_update_counter = 3;
    st->sid_handover_debt = 0;
    st->prev_ft = TX_SPEECH_GOOD;
}

int sid_sync_set_handover_debt (sid_syncState *st,
                                Word16 debtFrames) 
{
   /* debtFrames >= 0 */ 
   st->sid_handover_debt = debtFrames;
   return 0;
}

void sid_sync (sid_syncState *st, enum Mode mode,
               enum TXFrameType *tx_frame_type)
{
    if (mode == MRDTX)
    {
        st->sid_update_counter--;
        if (st->prev_ft == TX_SPEECH_GOOD) 
        {
           *tx_frame_type = TX_SID_FIRST;
           st->sid_update_counter = 3;
        } 
        else 
        {
           /* TX_SID_UPDATE or TX_NO_DATA */
           if ((st->sid_handover_debt > 0) &&
               (st->sid_update_counter > 2) )
           {
              /* ensure extra updates are  properly delayed after 
                 a possible SID_FIRST */
              *tx_frame_type = TX_SID_UPDATE;
              st->sid_handover_debt--;
           }
           else 
           {
              if (st->sid_update_counter == 0)
              {
                 *tx_frame_type = TX_SID_UPDATE;
                 st->sid_update_counter = st->sid_update_rate;
              } else {
                 *tx_frame_type = TX_NO_DATA;
              }
           }
        }
    }
    else
    {
       st->sid_update_counter = st->sid_update_rate ;
       *tx_frame_type = TX_SPEECH_GOOD;
    }
    st->prev_ft = *tx_frame_type;
}