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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 7f99b8ed30e5
children
line wrap: on
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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             : gc_pred.h
*      Purpose          : codebook gain MA prediction
*
********************************************************************************
*/

#ifndef gc_pred_h
#define gc_pred_h "$Id $"
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "tw_amr.h"
#include "typedef.h"

/*
********************************************************************************
*                         LOCAL VARIABLES AND TABLES
********************************************************************************
*/
 
/*
********************************************************************************
*                         DEFINITION OF DATA TYPES
********************************************************************************
*/
typedef struct {
   Word16 past_qua_en[4];         /* normal MA predictor memory,         Q10 */
                                  /* (contains 20*log10(qua_err))            */
   Word16 past_qua_en_MR122[4];   /* MA predictor memory for MR122 mode, Q10 */
                                  /* (contains log2(qua_err))                */
} gc_predState;
 
/*
********************************************************************************
*                         DECLARATION OF PROTOTYPES
********************************************************************************
*/
 
void gc_pred_reset (gc_predState *st);
/* reset of codebook gain MA predictor state (i.e. set state memory to zero)
   returns 0 on success
 */

void
gc_pred_copy(
    gc_predState *st_src,  /* i : State struct                           */
    gc_predState *st_dest  /* o : State struct                           */
);

/*************************************************************************
 *
 * FUNCTION:  gc_pred()
 *
 * PURPOSE: MA prediction of the innovation energy
 *          (in dB/(20*log10(2))) with mean  removed).
 *
 *************************************************************************/
void gc_pred(
    gc_predState *st,   /* i/o: State struct                           */
    enum Mode mode,     /* i  : AMR mode                               */
    Word16 *code,       /* i  : innovative codebook vector (L_SUBFR)   */
                        /*      MR122: Q12, other modes: Q13           */
    Word16 *exp_gcode0, /* o  : exponent of predicted gain factor, Q0  */
    Word16 *frac_gcode0,/* o  : fraction of predicted gain factor  Q15 */
    Word16 *exp_en,     /* o  : exponent of innovation energy,     Q0  */
                        /*      (only calculated for MR795)            */
    Word16 *frac_en     /* o  : fraction of innovation energy,     Q15 */
                        /*      (only calculated for MR795)            */
);

/*************************************************************************
 *
 * FUNCTION:  gc_pred_update()
 *
 * PURPOSE: update MA predictor with last quantized energy
 *
 *************************************************************************/
void gc_pred_update(
    gc_predState *st,      /* i/o: State struct                     */
    Word16 qua_ener_MR122, /* i  : quantized energy for update, Q10 */
                           /*      (log2(qua_err))                  */
    Word16 qua_ener        /* i  : quantized energy for update, Q10 */
                           /*      (20*log10(qua_err))              */
);

/*************************************************************************
 *
 * FUNCTION:  gc_pred_average_limited()
 *
 * PURPOSE: get average of MA predictor state values (with a lower limit)
 *          [used in error concealment]
 *
 *************************************************************************/
void gc_pred_average_limited(
    gc_predState *st,       /* i: State struct                    */
    Word16 *ener_avg_MR122, /* o: averaged quantized energy,  Q10 */
                            /*    (log2(qua_err))                 */
    Word16 *ener_avg        /* o: averaged quantized energy,  Q10 */
                            /*    (20*log10(qua_err))             */
);

#endif