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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 5401aaf7acb0
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             : cor_h.h                                     
*      Purpose          : correlation functions for codebook search   
*                                                                     
*****************************************************************************
*/                                                                    
/*                                                                    
*****************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID          
*****************************************************************************
*/
#ifndef cor_h_h
#define cor_h_h "@(#)$Id $"
/*
*****************************************************************************
*                         INCLUDE FILES                                      
*****************************************************************************
*/                                                                           
#include "typedef.h"                                                         
#include "cnst.h"                                                            
                                                                             
/*                                                                           
*****************************************************************************
*                         DECLARATION OF PROTOTYPES                          
*****************************************************************************
*/
void cor_h_x (
    Word16 h[],     /* (i) : impulse response of weighted synthesis filter */
    Word16 x[],     /* (i) : target                                        */
    Word16 dn[],    /* (o) : correlation between target and h[]            */
    Word16 sf       /* (i) : scaling factor: 2 for 12.2, 1 for 7.4         */
);

void cor_h_x2 (
    Word16 h[],     /* (i) : impulse response of weighted synthesis filter */
    Word16 x[],     /* (i) : target                                        */
    Word16 dn[],    /* (o) : correlation between target and h[]            */
    Word16 sf,      /* (i) : scaling factor: 2 for 12.2, 1 for 7.4         */
    Word16 nb_track,/* (i) : the number of ACB tracks                      */
    Word16 step     /* (i) : step size from one pulse position to the next
                             in one track                                  */
);

void cor_h (
    Word16 h[],     /* (i) : impulse response of weighted synthesis filter */
    Word16 sign[],      /* (i) : sign of d[n]                              */
    Word16 rr[][L_CODE] /* (o) : matrix of autocorrelation                 */
);

#endif