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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 57b4053559ff
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             : cnst.h
*      Purpose          : Speech codec constant parameters
*                       :  (encoder, decoder, and postfilter)
*
*****************************************************************************
*/
#ifndef cnst_h
#define cnst_h "$Id $"

#define L_TOTAL      320       /* Total size of speech buffer.             */
#define L_WINDOW     240       /* Window size in LP analysis               */
#define L_FRAME      160       /* Frame size                               */
#define L_FRAME_BY2  80        /* Frame size divided by 2                  */
#define L_SUBFR      40        /* Subframe size                            */
#define L_CODE       40        /* codevector length                        */
#define NB_TRACK     5         /* number of tracks                         */
#define STEP         5         /* codebook step size                       */
#define NB_TRACK_MR102  4      /* number of tracks mode mr102              */
#define STEP_MR102      4      /* codebook step size mode mr102            */
#define M            10        /* Order of LP filter                       */
#define MP1          (M+1)     /* Order of LP filter + 1                   */
#define LSF_GAP      205       /* Minimum distance between LSF after quan-
                                  tization; 50 Hz = 205                    */
#define LSP_PRED_FAC_MR122 21299 /* MR122 LSP prediction factor (0.65 Q15) */
#define AZ_SIZE       (4*M+4)  /* Size of array of LP filters in 4 subfr.s */
#define PIT_MIN_MR122 18       /* Minimum pitch lag (MR122 mode)           */
#define PIT_MIN       20       /* Minimum pitch lag (all other modes)      */
#define PIT_MAX       143      /* Maximum pitch lag                        */
#define L_INTERPOL    (10+1)   /* Length of filter for interpolation       */
#define L_INTER_SRCH  4        /* Length of filter for CL LTP search
                                  interpolation                            */
        
#define MU       26214         /* Factor for tilt compensation filter 0.8  */
#define AGC_FAC  29491         /* Factor for automatic gain control 0.9    */
        
#define L_NEXT       40        /* Overhead in LP analysis                  */
#define SHARPMAX  13017        /* Maximum value of pitch sharpening        */
#define SHARPMIN  0            /* Minimum value of pitch sharpening        */
                                                                          
                                                                          
#define MAX_PRM_SIZE    57     /* max. num. of params                      */
#define MAX_SERIAL_SIZE 244    /* max. num. of serial bits                 */
                                                                          
#define GP_CLIP   15565        /* Pitch gain clipping = 0.95               */
#define N_FRAME   7            /* old pitch gains in average calculation   */

#define EHF_MASK 0x0008        /* encoder homing frame pattern             */

#endif