src/GSM610/code.c

/*
 * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
 * Universitaet Berlin.  See the accompanying file "COPYRIGHT" for
 * details.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
 */


#include	<stdlib.h>
#include	<string.h>

#include	"gsm610_priv.h"

/*
 *  4.2 FIXED POINT IMPLEMENTATION OF THE RPE-LTP CODER
 */

void Gsm_Coder (

	struct gsm_state	* State,

	int16_t	* s,	/* [0..159] samples		  	IN	*/

/*
 * The RPE-LTD coder works on a frame by frame basis.  The length of
 * the frame is equal to 160 samples.  Some computations are done
 * once per frame to produce at the output of the coder the
 * LARc [1..8] parameters which are the coded LAR coefficients and
 * also to realize the inverse filtering operation for the entire
 * frame (160 samples of signal d [0..159]).  These parts produce at
 * the output of the coder:
 */

	int16_t	* LARc,	/* [0..7] LAR coefficients		OUT	*/

/*
 * Procedure 4.2.11 to 4.2.18 are to be executed four times per
 * frame.  That means once for each sub-segment RPE-LTP analysis of
 * 40 samples.  These parts produce at the output of the coder:
 */

	int16_t	*Nc,	/* [0..3] LTP lag			OUT 	*/
	int16_t	*bc,	/* [0..3] coded LTP gain		OUT 	*/
	int16_t	*Mc,	/* [0..3] RPE grid selection		OUT     */
	int16_t	*xmaxc,	/* [0..3] Coded maximum amplitude	OUT	*/
	int16_t	*xMc	/* [13*4] normalized RPE samples	OUT	*/
)
{
	int	k ;
	int16_t	*dp = State->dp0 + 120 ;	/* [-120...-1] */
	int16_t	*dpp = dp ;					/* [0...39]	 */

	int16_t	so [160] ;

	Gsm_Preprocess (State, s, so) ;
	Gsm_LPC_Analysis (State, so, LARc) ;
	Gsm_Short_Term_Analysis_Filter (State, LARc, so) ;

	for (k = 0 ; k <= 3 ; k++, xMc += 13)
	{	Gsm_Long_Term_Predictor	(State,
					so+k*40,		/* d      [0..39] IN	*/
					dp,				/* dp  [-120..-1] IN	*/
					State->e + 5,	/* e      [0..39] OUT	*/
					dpp,			/* dpp    [0..39] OUT */
					Nc++,
					bc++) ;

		Gsm_RPE_Encoding (/*-S,-*/
					State->e + 5,	/* e	 ][0..39][IN/OUT */
					xmaxc++, Mc++, xMc) ;
		/*
		 * Gsm_Update_of_reconstructed_short_time_residual_signal
		 *			(dpp, State->e + 5, dp) ;
		 */

		{
			register int i ;
			for (i = 0 ; i <= 39 ; i++)
				dp [i] = GSM_ADD (State->e [5 + i], dpp [i]) ;
		}
		dp += 40 ;
		dpp += 40 ;

	}
	memcpy ((char *) State->dp0, (char *) (State->dp0 + 160),
		120 * sizeof (*State->dp0)) ;
}