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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 a37687c6ff22
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             : subframePostProc.h
*      Purpose          : Subframe post processing
*
********************************************************************************
*/
#ifndef spstproc_h
#define spstproc_h "$Id $"

/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "tw_amr.h"
#include "typedef.h"

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

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

int subframePostProc(
    Word16 *speech,   /* i   : speech segment                        */
    enum Mode mode,   /* i   : coder mode                            */
    Word16 i_subfr,   /* i   : Subframe nr                           */
    Word16 gain_pit,  /* i   : Pitch gain                       Q14  */
    Word16 gain_code, /* i   : Decoded innovation gain               */
    Word16 *Aq,       /* i   : A(z) quantized for the 4 subframes    */
    Word16 synth[],   /* i   : Local snthesis                        */
    Word16 xn[],      /* i   : Target vector for pitch search        */
    Word16 code[],    /* i   : Fixed codebook exitation              */
    Word16 y1[],      /* i   : Filtered adaptive exitation           */
    Word16 y2[],      /* i   : Filtered fixed codebook excitation    */
    Word16 *mem_syn,  /* i/o : memory of synthesis filter            */
    Word16 *mem_err,  /* o   : pointer to error signal               */
    Word16 *mem_w0,   /* o   : memory of weighting filter            */
    Word16 *exc,      /* o   : long term prediction residual         */
    Word16 *sharp     /* o   : pitch sharpening value                */
);

#endif