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libgsmhr1 RxFE: store CN R0+LPC separately from speech In the original GSM 06.06 code the ECU for speech mode is entirely separate from the CN generator, maintaining separate state. (The main intertie between them is the speech vs CN state variable, distinguishing between speech and CN BFIs, in addition to the CN-specific function of distinguishing between initial and update SIDs.) In the present RxFE implementation I initially thought that we could use the same saved_frame buffer for both ECU and CN, overwriting just the first 4 params (R0 and LPC) when a valid SID comes in. However, I now realize it was a bad idea: the original code has a corner case (long sequence of speech-mode BFIs to put the ECU in state 6, then SID and CN-mode BFIs, then a good speech frame) that would be broken by that buffer reuse approach. We could eliminate this corner case by resetting the ECU state when passing through a CN insertion period, but doing so would needlessly increase the behavioral diffs between GSM 06.06 and our version. Solution: use a separate CN-specific buffer for CN R0+LPC parameters, and match the behavior of GSM 06.06 code in this regard.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 13 Feb 2025 10:02:45 +0000
parents 7bef001cd8b8
children
line wrap: on
line source

/*
*****************************************************************************
*
*      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             : dec_amr.h
*      Purpose          : Speech decoder routine.
*
*****************************************************************************
*/
#ifndef dec_amr_h
#define dec_amr_h "$Id $"
 
/*
*****************************************************************************
*                         INCLUDE FILES
*****************************************************************************
*/
#include "tw_amr.h"
#include "typedef.h"
#include "cnst.h"
#include "dtx_dec.h"
#include "d_plsf.h"
#include "gc_pred.h"
#include "ec_gains.h"
#include "ph_disp.h"
#include "c_g_aver.h"
#include "bgnscd.h"
#include "lsp_avg.h"

/*
*****************************************************************************
*                         LOCAL VARIABLES AND TABLES
*****************************************************************************
*/
/*---------------------------------------------------------------*
 *    Postfilter constant parameters (defined in "cnst.h")       *
 *---------------------------------------------------------------*
 *   L_FRAME     : Frame size.                                   *
 *   PIT_MAX     : Maximum pitch lag.                            *
 *   L_INTERPOL  : Length of filter for interpolation.           *
 *   M           : LPC order.                                    *
 *---------------------------------------------------------------*/

/*
*****************************************************************************
*                         DEFINITION OF DATA TYPES
*****************************************************************************
*/
typedef struct{
  /* Excitation vector */
  Word16 old_exc[L_SUBFR + PIT_MAX + L_INTERPOL];
  Word16 *exc;
    
  /* Lsp (Line spectral pairs) */
   /* Word16 lsp[M]; */      /* Used by CN codec */
  Word16 lsp_old[M];
 
  /* Filter's memory */
  Word16 mem_syn[M];

  /* pitch sharpening */
  Word16 sharp;
  Word16 old_T0;

  /* Memories for bad frame handling */
  Word16 prev_bf;
  Word16 prev_pdf;   
  Word16 state;
  Word16 excEnergyHist[9];

  /* Variable holding received ltpLag, used in background noise and BFI */
  Word16 T0_lagBuff;

  /* Variables for the source characteristic detector (SCD) */
  Word16 inBackgroundNoise;
  Word16 voicedHangover;
  Word16 ltpGainHistory[9];

  Bgn_scdState background_state;
  Word16 nodataSeed;

  Cb_gain_averageState Cb_gain_averState;
  lsp_avgState lsp_avg_st;

  D_plsfState lsfState;
  ec_gain_pitchState ec_gain_p_st;
  ec_gain_codeState ec_gain_c_st;  
  gc_predState pred_state;
  ph_dispState ph_disp_st;
  dtx_decState dtxDecoderState;
} Decoder_amrState;
 

/*
*****************************************************************************
*                         DECLARATION OF PROTOTYPES
*****************************************************************************
*/
 
/*
**************************************************************************
*
*  Function    : Decoder_amr_reset
*  Purpose     : Resets state memory
*  Returns     : 0 on success
*
**************************************************************************
*/
void Decoder_amr_reset (Decoder_amrState *st, Flag dtx_partial_reset);
 
/*
**************************************************************************
*
*  Function    : Decoder_amr
*  Purpose     : Speech decoder routine.
*  Returns     : 0
*
**************************************************************************
*/
int Decoder_amr (
    Decoder_amrState *st,  /* i/o : State variables                       */
    enum Mode mode,        /* i   : AMR mode                              */
    Word16 parm[],         /* i   : vector of synthesis parameters
                                    (PRM_SIZE)                            */
    enum RXFrameType frame_type, /* i   : received frame type               */
    Word16 synth[],        /* o   : synthesis speech (L_FRAME)            */
    Word16 A_t[]           /* o   : decoded LP filter in 4 subframes
                                    (AZ_SIZE)                             */
);

#endif