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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 b02e043dcba0
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             : qua_gain.h
*      Purpose          : Quantization of pitch and codebook gains.
*
********************************************************************************
*/
#ifndef qua_gain_h
#define qua_gain_h "$Id $"
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "tw_amr.h"
#include "typedef.h"

/*
********************************************************************************
*                         DECLARATION OF PROTOTYPES
********************************************************************************
*/
/*************************************************************************
 *
 * FUNCTION:  Qua_gain()
 *
 * PURPOSE: Quantization of pitch and codebook gains.
 *          (using predicted codebook gain)
 *
 *************************************************************************/
Word16
Qua_gain(                   /* o  : index of quantization.                 */   
    enum Mode mode,         /* i  : AMR mode                               */
    Word16 exp_gcode0,      /* i  : predicted CB gain (exponent),      Q0  */
    Word16 frac_gcode0,     /* i  : predicted CB gain (fraction),      Q15 */
    Word16 frac_coeff[],    /* i  : energy coeff. (5), fraction part,  Q15 */
    Word16 exp_coeff[],     /* i  : energy coeff. (5), exponent part,  Q0  */
                            /*      (frac_coeff and exp_coeff computed in  */
                            /*       calc_filt_energies())                 */
    Word16 gp_limit,        /* i  : pitch gain limit                       */
    Word16 *gain_pit,       /* o  : Pitch gain,                        Q14 */
    Word16 *gain_cod,       /* o  : Code gain,                         Q1  */
    Word16 *qua_ener_MR122, /* o  : quantized energy error,            Q10 */
                            /*      (for MR122 MA predictor update)        */
    Word16 *qua_ener        /* o  : quantized energy error,            Q10 */
                            /*      (for other MA predictor update)        */
);
#endif