RTL271_1/amrnb/g_adapt.h

/*
********************************************************************************
*
*      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             : g_adapt.h
*      Purpose          : gain adaptation for MR795 gain quantization
*
********************************************************************************
*/

/*
********************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
********************************************************************************
*/
#ifndef g_adapt_h
#define g_adapt_h "$Id $"

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

#define LTPG_MEM_SIZE 5 /* number of stored past LTP coding gains + 1 */

/*
********************************************************************************
*                         DEFINITION OF DATA TYPES
********************************************************************************
*/
typedef struct {
    Word16 onset;                   /* onset state,                   Q0  */
    Word16 prev_alpha;              /* previous adaptor output,       Q15 */
    Word16 prev_gc;                 /* previous code gain,            Q1  */

    Word16 ltpg_mem[LTPG_MEM_SIZE]; /* LTP coding gain history,       Q13 */
                                    /* (ltpg_mem[0] not used for history) */
} GainAdaptState;
 
/*
********************************************************************************
*                         DECLARATION OF PROTOTYPES
********************************************************************************
*/
int gain_adapt_init (GainAdaptState **st);
/* initialize one instance of the gain adaptor
   Stores pointer to state struct in *st. This pointer has to
   be passed to gain_adapt and gain_adapt_update in each call.
   returns 0 on success
 */
 
int gain_adapt_reset (GainAdaptState *st);
/* reset of gain adaptor state (i.e. set state memory to zero)
   returns 0 on success
 */

void gain_adapt_exit (GainAdaptState **st);
/* de-initialize gain adaptor state (i.e. free state struct)
   stores NULL in *st
 */

/*************************************************************************
 *
 *  Function:   gain_adapt()
 *  Purpose:    calculate pitch/codebook gain adaptation factor alpha
 *              (and update the adaptor state)
 *
 **************************************************************************
 */
void gain_adapt(
    GainAdaptState *st,  /* i  : state struct                  */
    Word16 ltpg,         /* i  : ltp coding gain (log2()), Q   */
    Word16 gain_cod,     /* i  : code gain,                Q13 */
    Word16 *alpha        /* o  : gain adaptation factor,   Q15 */
);


#endif