--- a/libgsmfr2/Makefile	Sun Apr 14 00:36:16 2024 +0000
+++ b/libgsmfr2/Makefile	Sun Apr 14 01:01:19 2024 +0000
@@ -1,8 +1,8 @@
 CC=	gcc
 CFLAGS=	-O2
-OBJS=	add.o comfort_noise.o dec_main.o ed_state.o enc_main.o pack_frame.o \
-	pack_frame2.o pp_bad.o pp_good.o pp_state.o prng.o sidclass.o \
-	silence_frame.o unpack_frame.o unpack_frame2.o xmaxc_mean.o
+OBJS=	add.o comfort_noise.o dec_main.o ed_state.o enc_main.o long_term.o \
+	pack_frame.o pack_frame2.o pp_bad.o pp_good.o pp_state.o prng.o \
+	sidclass.o silence_frame.o unpack_frame.o unpack_frame2.o xmaxc_mean.o
 HDRS=	ed_internal.h ed_state.h pp_internal.h pp_state.h tw_gsmfr.h typedef.h
 LIB=	libgsmfr2.a
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmfr2/long_term.c	Sun Apr 14 01:01:19 2024 +0000
@@ -0,0 +1,266 @@
+/*
+ * This C source file has been adapted from TU-Berlin libgsm source,
+ * original notice follows:
+ *
+ * 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 <stdint.h>
+#include <assert.h>
+#include "tw_gsmfr.h"
+#include "typedef.h"
+#include "ed_state.h"
+#include "ed_internal.h"
+
+/*
+ *  4.2.11 .. 4.2.12 LONG TERM PREDICTOR (LTP) SECTION
+ */
+
+
+/*
+ * This module computes the LTP gain (bc) and the LTP lag (Nc)
+ * for the long term analysis filter.   This is done by calculating a
+ * maximum of the cross-correlation function between the current
+ * sub-segment short term residual signal d[0..39] (output of
+ * the short term analysis filter; for simplification the index
+ * of this array begins at 0 and ends at 39 for each sub-segment of the
+ * RPE-LTP analysis) and the previous reconstructed short term
+ * residual signal dp[ -120 .. -1 ].  A dynamic scaling must be
+ * performed to avoid overflow.
+ */
+
+static void Calculation_of_the_LTP_parameters (
+	register word	* d,		/* [0..39]	IN	*/
+	register word	* dp,		/* [-120..-1]	IN	*/
+	word		* bc_out,	/* 		OUT	*/
+	word		* Nc_out	/* 		OUT	*/
+)
+{
+	register int  	k, lambda;
+	word		Nc, bc;
+	word		wt[40];
+
+	longword	L_max, L_power;
+	word		R, S, dmax, scal;
+	register word	temp;
+
+	/*  Search of the optimum scaling of d[0..39].
+	 */
+	dmax = 0;
+
+	for (k = 0; k <= 39; k++) {
+		temp = d[k];
+		temp = GSM_ABS( temp );
+		if (temp > dmax) dmax = temp;
+	}
+
+	temp = 0;
+	if (dmax == 0) scal = 0;
+	else {
+		assert(dmax > 0);
+		temp = gsm_norm( (longword)dmax << 16 );
+	}
+
+	if (temp > 6) scal = 0;
+	else scal = 6 - temp;
+
+	assert(scal >= 0);
+
+	/*  Initialization of a working array wt
+	 */
+
+	for (k = 0; k <= 39; k++) wt[k] = SASR( d[k], scal );
+
+	/* Search for the maximum cross-correlation and coding of the LTP lag
+	 */
+	L_max = 0;
+	Nc    = 40;	/* index for the maximum cross-correlation */
+
+	for (lambda = 40; lambda <= 120; lambda++) {
+
+# undef STEP
+#		define STEP(k) 	(longword)wt[k] * dp[k - lambda]
+
+		register longword L_result;
+
+		L_result  = STEP(0)  ; L_result += STEP(1) ;
+		L_result += STEP(2)  ; L_result += STEP(3) ;
+		L_result += STEP(4)  ; L_result += STEP(5)  ;
+		L_result += STEP(6)  ; L_result += STEP(7)  ;
+		L_result += STEP(8)  ; L_result += STEP(9)  ;
+		L_result += STEP(10) ; L_result += STEP(11) ;
+		L_result += STEP(12) ; L_result += STEP(13) ;
+		L_result += STEP(14) ; L_result += STEP(15) ;
+		L_result += STEP(16) ; L_result += STEP(17) ;
+		L_result += STEP(18) ; L_result += STEP(19) ;
+		L_result += STEP(20) ; L_result += STEP(21) ;
+		L_result += STEP(22) ; L_result += STEP(23) ;
+		L_result += STEP(24) ; L_result += STEP(25) ;
+		L_result += STEP(26) ; L_result += STEP(27) ;
+		L_result += STEP(28) ; L_result += STEP(29) ;
+		L_result += STEP(30) ; L_result += STEP(31) ;
+		L_result += STEP(32) ; L_result += STEP(33) ;
+		L_result += STEP(34) ; L_result += STEP(35) ;
+		L_result += STEP(36) ; L_result += STEP(37) ;
+		L_result += STEP(38) ; L_result += STEP(39) ;
+
+		if (L_result > L_max) {
+
+			Nc    = lambda;
+			L_max = L_result;
+		}
+	}
+
+	*Nc_out = Nc;
+
+	L_max <<= 1;
+
+	/*  Rescaling of L_max
+	 */
+	assert(scal <= 100 && scal >=  -100);
+	L_max = L_max >> (6 - scal);	/* sub(6, scal) */
+
+	assert( Nc <= 120 && Nc >= 40);
+
+	/*   Compute the power of the reconstructed short term residual
+	 *   signal dp[..]
+	 */
+	L_power = 0;
+	for (k = 0; k <= 39; k++) {
+
+		register longword L_temp;
+
+		L_temp   = SASR( dp[k - Nc], 3 );
+		L_power += L_temp * L_temp;
+	}
+	L_power <<= 1;	/* from L_MULT */
+
+	/*  Normalization of L_max and L_power
+	 */
+
+	if (L_max <= 0)  {
+		*bc_out = 0;
+		return;
+	}
+	if (L_max >= L_power) {
+		*bc_out = 3;
+		return;
+	}
+
+	temp = gsm_norm( L_power );
+
+	R = SASR( L_max   << temp, 16 );
+	S = SASR( L_power << temp, 16 );
+
+	/*  Coding of the LTP gain
+	 */
+
+	/*  Table 4.3a must be used to obtain the level DLB[i] for the
+	 *  quantization of the LTP gain b to get the coded version bc.
+	 */
+	for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break;
+	*bc_out = bc;
+}
+
+/* 4.2.12 */
+
+static void Long_term_analysis_filtering (
+	word		bc,	/* 					IN  */
+	word		Nc,	/* 					IN  */
+	register word	* dp,	/* previous d	[-120..-1]		IN  */
+	register word	* d,	/* d		[0..39]			IN  */
+	register word	* dpp,	/* estimate	[0..39]			OUT */
+	register word	* e	/* long term res. signal [0..39]	OUT */
+)
+/*
+ *  In this part, we have to decode the bc parameter to compute
+ *  the samples of the estimate dpp[0..39].  The decoding of bc needs the
+ *  use of table 4.3b.  The long term residual signal e[0..39]
+ *  is then calculated to be fed to the RPE encoding section.
+ */
+{
+	register int      k;
+	register longword ltmp;
+
+#	undef STEP
+#	define STEP(BP)					\
+	for (k = 0; k <= 39; k++) {			\
+		dpp[k]  = GSM_MULT_R( BP, dp[k - Nc]);	\
+		e[k]	= GSM_SUB( d[k], dpp[k] );	\
+	}
+
+	switch (bc) {
+	case 0:	STEP(  3277 ); break;
+	case 1:	STEP( 11469 ); break;
+	case 2: STEP( 21299 ); break;
+	case 3: STEP( 32767 ); break;
+	}
+}
+
+void Gsm_Long_Term_Predictor (		/* 4x for 160 samples */
+	struct gsmfr_0610_state	* S,
+
+	word	* d,	/* [0..39]   residual signal	IN	*/
+	word	* dp,	/* [-120..-1] d'		IN	*/
+
+	word	* e,	/* [0..39] 			OUT	*/
+	word	* dpp,	/* [0..39] 			OUT	*/
+	word	* Nc,	/* correlation lag		OUT	*/
+	word	* bc	/* gain factor			OUT	*/
+)
+{
+	assert( d  ); assert( dp ); assert( e  );
+	assert( dpp); assert( Nc ); assert( bc );
+
+	Calculation_of_the_LTP_parameters(d, dp, bc, Nc);
+	Long_term_analysis_filtering( *bc, *Nc, dp, d, dpp, e );
+}
+
+/* 4.3.2 */
+void Gsm_Long_Term_Synthesis_Filtering (
+	struct gsmfr_0610_state	* S,
+
+	word			Ncr,
+	word			bcr,
+	register word		* erp,	   /* [0..39]		  	 IN */
+	register word		* drp	   /* [-120..-1] IN, [-120..40] OUT */
+)
+/*
+ *  This procedure uses the bcr and Ncr parameter to realize the
+ *  long term synthesis filtering.  The decoding of bcr needs
+ *  table 4.3b.
+ */
+{
+	register longword	ltmp;	/* for ADD */
+	register int 		k;
+	word			brp, drpp, Nr;
+
+	/*  Check the limits of Nr.
+	 */
+	Nr = Ncr < 40 || Ncr > 120 ? S->nrp : Ncr;
+	S->nrp = Nr;
+	assert(Nr >= 40 && Nr <= 120);
+
+	/*  Decoding of the LTP gain bcr
+	 */
+	brp = gsm_QLB[ bcr ];
+
+	/*  Computation of the reconstructed short term residual
+	 *  signal drp[0..39]
+	 */
+	assert(brp != MIN_WORD);
+
+	for (k = 0; k <= 39; k++) {
+		drpp   = GSM_MULT_R( brp, drp[ k - Nr ] );
+		drp[k] = GSM_ADD( erp[k], drpp );
+	}
+
+	/*
+	 *  Update of the reconstructed short term residual signal
+	 *  drp[ -1..-120 ]
+	 */
+
+	for (k = 0; k <= 119; k++) drp[ -120 + k ] = drp[ -80 + k ];
+}