+
−/*
+
−********************************************************************************
+
−*
+
−*      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             : levinson.h
+
−*      Purpose          : Levinson-Durbin algorithm in double precision.
+
−*                       : To compute the LP filter parameters from the
+
−*                       : speech autocorrelations.
+
−*
+
−********************************************************************************
+
−*/
+
−#ifndef levinson_h
+
−#define levinson_h "$Id $"
+
− 
+
−/*
+
−********************************************************************************
+
−*                         INCLUDE FILES
+
−********************************************************************************
+
−*/
+
−#include "typedef.h"
+
−#include "cnst.h"
+
− 
+
−/*
+
−********************************************************************************
+
−*                         LOCAL VARIABLES AND TABLES
+
−********************************************************************************
+
−*/
+
− 
+
−/*
+
−********************************************************************************
+
−*                         DEFINITION OF DATA TYPES
+
−********************************************************************************
+
−*/
+
−typedef struct {
+
−  Word16 old_A[M + 1];     /* Last A(z) for case of unstable filter */
+
−} LevinsonState;
+
− 
+
−/*
+
−********************************************************************************
+
−*                         DECLARATION OF PROTOTYPES
+
−********************************************************************************
+
−*/
+
− 
+
−void Levinson_reset (LevinsonState *st);
+
−/* reset of pre processing state (i.e. set state memory to zero)
+
−   returns 0 on success
+
− */
+
−
+
−int Levinson (
+
−    LevinsonState *st,
+
−    Word16 Rh[],       /* i : Rh[m+1] Vector of autocorrelations (msb) */
+
−    Word16 Rl[],       /* i : Rl[m+1] Vector of autocorrelations (lsb) */
+
−    Word16 A[],        /* o : A[m]    LPC coefficients  (m = 10)       */
+
−    Word16 rc[]        /* o : rc[4]   First 4 reflection coefficients  */
+
−);
+
− 
+
−#endif