RTL271_1/amrnb/int_lsf.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             : int_lsf.h
*      Purpose          : Interpolates the LSFs
*
********************************************************************************
*/
#ifndef int_lsf_h
#define int_lsf_h "$Id $"
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "typedef.h"
 
/*
********************************************************************************
*                         DEFINITION OF DATA TYPES
********************************************************************************
*/
 
/*
********************************************************************************
*                         DECLARATION OF PROTOTYPES
********************************************************************************
*/

/*
**************************************************************************
*
*  Function    : Int_lsf
*  Purpose     : Interpolates the LSFs for selected subframe
*  Description : The 20 ms speech frame is divided into 4 subframes.
*                The LSFs are interpolated at the 1st, 2nd and 3rd
*                subframe and only forwarded at the 4th subframe.
*
*                      |------|------|------|------|
*                         sf1    sf2    sf3    sf4
*                   F0                          F1
*      
*                 sf1:   3/4 F0 + 1/4 F1         sf3:   1/4 F0 + 3/4 F1
*                 sf2:   1/2 F0 + 1/2 F1         sf4:       F1
*  Returns     : void
*
**************************************************************************
*/
void Int_lsf (
    Word16 lsf_old[], /* i : LSF vector at the 4th SF of past frame          */
    Word16 lsf_new[], /* i : LSF vector at the 4th SF of present frame       */
    Word16 i_subfr,   /* i : Pointer to current sf (equal to 0,40,80 or 120) */
    Word16 lsf_out[]  /* o : interpolated LSF parameters for current sf      */
);
 
#endif