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view libgsmefr/cnst.h @ 242:f081a6850fb5

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libgsmfrp: new refined implementation The previous implementation exhibited the following defects, which are now fixed: 1) The last received valid SID was cached forever for the purpose of handling future invalid SIDs - we could have received some valid SID ages ago, then lots of speech or NO_DATA, and if we then get an invalid SID, we would resurrect the last valid SID from ancient history - a bad design. In our new design, we handle invalid SID based on the current state, much like BFI. 2) GSM 06.11 spec says clearly that after the second lost SID (received BFI=1 && TAF=1 in CN state) we need to gradually decrease the output level, rather than jump directly to emitting silence frames - we previously failed to implement such logic. 3) Per GSM 06.12 section 5.2, Xmaxc should be the same in all 4 subframes in a SID frame. What should we do if we receive an otherwise valid SID frame with different Xmaxc? Our previous approach would replicate this Xmaxc oddity in every subsequent generated CN frame, which is rather bad. In our new design, the very first CN frame (which can be seen as a transformation of the SID frame itself) retains the original 4 distinct Xmaxc, but all subsequent CN frames are based on the Xmaxc from the last subframe of the most recent SID.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 09 May 2023 05:16:31 +0000
parents f9c9dd458d55
children
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/*--------------------------------------------------------------------------*
*       Codec constant parameters (coder, decoder, and postfilter)          *
*---------------------------------------------------------------------------*/

#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  M            10        /* Order of LP filter                       */
#define  MP1          (M+1)     /* Order of LP filter + 1                   */
#define  AZ_SIZE      (4*M+4)   /* Size of array of LP filters in 4 subfr.s */
#define  PIT_MIN      18        /* Minimum pitch lag                        */
#define  PIT_MAX      143       /* Maximum pitch lag                        */
#define  L_INTERPOL   (10+1)    /* Length of filter for interpolation       */

#define  PRM_SIZE     57        /* Size of vector of analysis parameters    */

#define  MU       26214         /* Factor for tilt compensation filter 0.8  */
#define  AGC_FAC  29491         /* Factor for automatic gain control 0.9    */

#define DTX_HANGOVER 7                /* Period when SP=1 although VAD=0.
                                         Used for comfort noise averaging */