diff --git a/third_party/gsm/src/rpe.c b/third_party/gsm/src/rpe.c
new file mode 100644
index 0000000..eda4f18
--- /dev/null
+++ b/third_party/gsm/src/rpe.c
@@ -0,0 +1,488 @@
+/*
+ * 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.
+ */
+
+/* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/rpe.c,v 1.3 1994/05/10 20:18:46 jutta Exp $ */
+
+#include <stdio.h>
+#include <assert.h>
+
+#include "private.h"
+
+#include "gsm.h"
+#include "proto.h"
+
+/*  4.2.13 .. 4.2.17  RPE ENCODING SECTION
+ */
+
+/* 4.2.13 */
+
+static void Weighting_filter P2((e, x),
+	register word	* e,		/* signal [-5..0.39.44]	IN  */
+	word		* x		/* signal [0..39]	OUT */
+)
+/*
+ *  The coefficients of the weighting filter are stored in a table
+ *  (see table 4.4).  The following scaling is used:
+ *
+ *	H[0..10] = integer( real_H[ 0..10] * 8192 ); 
+ */
+{
+	/* word			wt[ 50 ]; */
+
+	register longword	L_result;
+	register int		k /* , i */ ;
+
+	/*  Initialization of a temporary working array wt[0...49]
+	 */
+
+	/* for (k =  0; k <=  4; k++) wt[k] = 0;
+	 * for (k =  5; k <= 44; k++) wt[k] = *e++;
+	 * for (k = 45; k <= 49; k++) wt[k] = 0;
+	 *
+	 *  (e[-5..-1] and e[40..44] are allocated by the caller,
+	 *  are initially zero and are not written anywhere.)
+	 */
+	e -= 5;
+
+	/*  Compute the signal x[0..39]
+	 */ 
+	for (k = 0; k <= 39; k++) {
+
+		L_result = 8192 >> 1;
+
+		/* for (i = 0; i <= 10; i++) {
+		 *	L_temp   = GSM_L_MULT( wt[k+i], gsm_H[i] );
+		 *	L_result = GSM_L_ADD( L_result, L_temp );
+		 * }
+		 */
+
+#undef	STEP
+#define	STEP( i, H )	(e[ k + i ] * (longword)H)
+
+		/*  Every one of these multiplications is done twice --
+		 *  but I don't see an elegant way to optimize this. 
+		 *  Do you?
+		 */
+
+#ifdef	STUPID_COMPILER
+		L_result += STEP(	0, 	-134 ) ;
+		L_result += STEP(	1, 	-374 )  ;
+	               /* + STEP(	2, 	0    )  */
+		L_result += STEP(	3, 	2054 ) ;
+		L_result += STEP(	4, 	5741 ) ;
+		L_result += STEP(	5, 	8192 ) ;
+		L_result += STEP(	6, 	5741 ) ;
+		L_result += STEP(	7, 	2054 ) ;
+	 	       /* + STEP(	8, 	0    )  */
+		L_result += STEP(	9, 	-374 ) ;
+		L_result += STEP(	10, 	-134 ) ;
+#else
+		L_result +=
+		  STEP(	0, 	-134 ) 
+		+ STEP(	1, 	-374 ) 
+	     /* + STEP(	2, 	0    )  */
+		+ STEP(	3, 	2054 ) 
+		+ STEP(	4, 	5741 ) 
+		+ STEP(	5, 	8192 ) 
+		+ STEP(	6, 	5741 ) 
+		+ STEP(	7, 	2054 ) 
+	     /* + STEP(	8, 	0    )  */
+		+ STEP(	9, 	-374 ) 
+		+ STEP(10, 	-134 )
+		;
+#endif
+
+		/* L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x2) *)
+		 * L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x4) *)
+		 *
+		 * x[k] = SASR( L_result, 16 );
+		 */
+
+		/* 2 adds vs. >>16 => 14, minus one shift to compensate for
+		 * those we lost when replacing L_MULT by '*'.
+		 */
+
+		L_result = SASR( L_result, 13 );
+		x[k] =  (  L_result < MIN_WORD ? MIN_WORD
+			: (L_result > MAX_WORD ? MAX_WORD : L_result ));
+	}
+}
+
+/* 4.2.14 */
+
+static void RPE_grid_selection P3((x,xM,Mc_out),
+	word		* x,		/* [0..39]		IN  */ 
+	word		* xM,		/* [0..12]		OUT */
+	word		* Mc_out	/*			OUT */
+)
+/*
+ *  The signal x[0..39] is used to select the RPE grid which is
+ *  represented by Mc.
+ */
+{
+	/* register word	temp1;	*/
+	register int		/* m, */  i;
+	register longword	L_result, L_temp;
+	longword		EM;	/* xxx should be L_EM? */
+	word			Mc;
+
+	longword		L_common_0_3;
+
+	EM = 0;
+	Mc = 0;
+
+	/* for (m = 0; m <= 3; m++) {
+	 *	L_result = 0;
+	 *
+	 *
+	 *	for (i = 0; i <= 12; i++) {
+	 *
+	 *		temp1    = SASR( x[m + 3*i], 2 );
+	 *
+	 *		assert(temp1 != MIN_WORD);
+	 *
+	 *		L_temp   = GSM_L_MULT( temp1, temp1 );
+	 *		L_result = GSM_L_ADD( L_temp, L_result );
+	 *	}
+	 * 
+	 *	if (L_result > EM) {
+	 *		Mc = m;
+	 *		EM = L_result;
+	 *	}
+	 * }
+	 */
+
+#undef	STEP
+#define	STEP( m, i )		L_temp = SASR( x[m + 3 * i], 2 );	\
+				L_result += L_temp * L_temp;
+
+	/* common part of 0 and 3 */
+
+	L_result = 0;
+	STEP( 0, 1 ); STEP( 0, 2 ); STEP( 0, 3 ); STEP( 0, 4 );
+	STEP( 0, 5 ); STEP( 0, 6 ); STEP( 0, 7 ); STEP( 0, 8 );
+	STEP( 0, 9 ); STEP( 0, 10); STEP( 0, 11); STEP( 0, 12);
+	L_common_0_3 = L_result;
+
+	/* i = 0 */
+
+	STEP( 0, 0 );
+	L_result <<= 1;	/* implicit in L_MULT */
+	EM = L_result;
+
+	/* i = 1 */
+
+	L_result = 0;
+	STEP( 1, 0 );
+	STEP( 1, 1 ); STEP( 1, 2 ); STEP( 1, 3 ); STEP( 1, 4 );
+	STEP( 1, 5 ); STEP( 1, 6 ); STEP( 1, 7 ); STEP( 1, 8 );
+	STEP( 1, 9 ); STEP( 1, 10); STEP( 1, 11); STEP( 1, 12);
+	L_result <<= 1;
+	if (L_result > EM) {
+		Mc = 1;
+	 	EM = L_result;
+	}
+
+	/* i = 2 */
+
+	L_result = 0;
+	STEP( 2, 0 );
+	STEP( 2, 1 ); STEP( 2, 2 ); STEP( 2, 3 ); STEP( 2, 4 );
+	STEP( 2, 5 ); STEP( 2, 6 ); STEP( 2, 7 ); STEP( 2, 8 );
+	STEP( 2, 9 ); STEP( 2, 10); STEP( 2, 11); STEP( 2, 12);
+	L_result <<= 1;
+	if (L_result > EM) {
+		Mc = 2;
+	 	EM = L_result;
+	}
+
+	/* i = 3 */
+
+	L_result = L_common_0_3;
+	STEP( 3, 12 );
+	L_result <<= 1;
+	if (L_result > EM) {
+		Mc = 3;
+	 	EM = L_result;
+	}
+
+	/**/
+
+	/*  Down-sampling by a factor 3 to get the selected xM[0..12]
+	 *  RPE sequence.
+	 */
+	for (i = 0; i <= 12; i ++) xM[i] = x[Mc + 3*i];
+	*Mc_out = Mc;
+}
+
+/* 4.12.15 */
+
+static void APCM_quantization_xmaxc_to_exp_mant P3((xmaxc,exp_out,mant_out),
+	word		xmaxc,		/* IN 	*/
+	word		* exp_out,	/* OUT	*/
+	word		* mant_out )	/* OUT  */
+{
+	word	exp, mant;
+
+	/* Compute exponent and mantissa of the decoded version of xmaxc
+	 */
+
+	exp = 0;
+	if (xmaxc > 15) exp = SASR(xmaxc, 3) - 1;
+	mant = xmaxc - (exp << 3);
+
+	if (mant == 0) {
+		exp  = -4;
+		mant = 7;
+	}
+	else {
+		while (mant <= 7) {
+			mant = mant << 1 | 1;
+			exp--;
+		}
+		mant -= 8;
+	}
+
+	assert( exp  >= -4 && exp <= 6 );
+	assert( mant >= 0 && mant <= 7 );
+
+	*exp_out  = exp;
+	*mant_out = mant;
+}
+
+static void APCM_quantization P5((xM,xMc,mant_out,exp_out,xmaxc_out),
+	word		* xM,		/* [0..12]		IN	*/
+
+	word		* xMc,		/* [0..12]		OUT	*/
+	word		* mant_out,	/* 			OUT	*/
+	word		* exp_out,	/*			OUT	*/
+	word		* xmaxc_out	/*			OUT	*/
+)
+{
+	int	i, itest;
+
+	word	xmax, xmaxc, temp, temp1, temp2;
+	word	exp, mant;
+
+
+	/*  Find the maximum absolute value xmax of xM[0..12].
+	 */
+
+	xmax = 0;
+	for (i = 0; i <= 12; i++) {
+		temp = xM[i];
+		temp = GSM_ABS(temp);
+		if (temp > xmax) xmax = temp;
+	}
+
+	/*  Qantizing and coding of xmax to get xmaxc.
+	 */
+
+	exp   = 0;
+	temp  = SASR( xmax, 9 );
+	itest = 0;
+
+	for (i = 0; i <= 5; i++) {
+
+		itest |= (temp <= 0);
+		temp = SASR( temp, 1 );
+
+		assert(exp <= 5);
+		if (itest == 0) exp++;		/* exp = add (exp, 1) */
+	}
+
+	assert(exp <= 6 && exp >= 0);
+	temp = exp + 5;
+
+	assert(temp <= 11 && temp >= 0);
+	xmaxc = gsm_add( SASR(xmax, temp), exp << 3 );
+
+	/*   Quantizing and coding of the xM[0..12] RPE sequence
+	 *   to get the xMc[0..12]
+	 */
+
+	APCM_quantization_xmaxc_to_exp_mant( xmaxc, &exp, &mant );
+
+	/*  This computation uses the fact that the decoded version of xmaxc
+	 *  can be calculated by using the exponent and the mantissa part of
+	 *  xmaxc (logarithmic table).
+	 *  So, this method avoids any division and uses only a scaling
+	 *  of the RPE samples by a function of the exponent.  A direct 
+	 *  multiplication by the inverse of the mantissa (NRFAC[0..7]
+	 *  found in table 4.5) gives the 3 bit coded version xMc[0..12]
+	 *  of the RPE samples.
+	 */
+
+
+	/* Direct computation of xMc[0..12] using table 4.5
+	 */
+
+	assert( exp <= 4096 && exp >= -4096);
+	assert( mant >= 0 && mant <= 7 ); 
+
+	temp1 = 6 - exp;		/* normalization by the exponent */
+	temp2 = gsm_NRFAC[ mant ];  	/* inverse mantissa 		 */
+
+	for (i = 0; i <= 12; i++) {
+
+		assert(temp1 >= 0 && temp1 < 16);
+
+		temp = xM[i] << temp1;
+		temp = GSM_MULT( temp, temp2 );
+		temp = SASR(temp, 12);
+		xMc[i] = temp + 4;		/* see note below */
+	}
+
+	/*  NOTE: This equation is used to make all the xMc[i] positive.
+	 */
+
+	*mant_out  = mant;
+	*exp_out   = exp;
+	*xmaxc_out = xmaxc;
+}
+
+/* 4.2.16 */
+
+static void APCM_inverse_quantization P4((xMc,mant,exp,xMp),
+	register word	* xMc,	/* [0..12]			IN 	*/
+	word		mant,
+	word		exp,
+	register word	* xMp)	/* [0..12]			OUT 	*/
+/* 
+ *  This part is for decoding the RPE sequence of coded xMc[0..12]
+ *  samples to obtain the xMp[0..12] array.  Table 4.6 is used to get
+ *  the mantissa of xmaxc (FAC[0..7]).
+ */
+{
+	int	i;
+	word	temp, temp1, temp2, temp3;
+	longword	ltmp;
+
+	assert( mant >= 0 && mant <= 7 ); 
+
+	temp1 = gsm_FAC[ mant ];	/* see 4.2-15 for mant */
+	temp2 = gsm_sub( 6, exp );	/* see 4.2-15 for exp  */
+	temp3 = gsm_asl( 1, gsm_sub( temp2, 1 ));
+
+	for (i = 13; i--;) {
+
+		assert( *xMc <= 7 && *xMc >= 0 ); 	/* 3 bit unsigned */
+
+		/* temp = gsm_sub( *xMc++ << 1, 7 ); */
+		temp = (*xMc++ << 1) - 7;	        /* restore sign   */
+		assert( temp <= 7 && temp >= -7 ); 	/* 4 bit signed   */
+
+		temp <<= 12;				/* 16 bit signed  */
+		temp = GSM_MULT_R( temp1, temp );
+		temp = GSM_ADD( temp, temp3 );
+		*xMp++ = gsm_asr( temp, temp2 );
+	}
+}
+
+/* 4.2.17 */
+
+static void RPE_grid_positioning P3((Mc,xMp,ep),
+	word		Mc,		/* grid position	IN	*/
+	register word	* xMp,		/* [0..12]		IN	*/
+	register word	* ep		/* [0..39]		OUT	*/
+)
+/*
+ *  This procedure computes the reconstructed long term residual signal
+ *  ep[0..39] for the LTP analysis filter.  The inputs are the Mc
+ *  which is the grid position selection and the xMp[0..12] decoded
+ *  RPE samples which are upsampled by a factor of 3 by inserting zero
+ *  values.
+ */
+{
+	int	i = 13;
+
+	assert(0 <= Mc && Mc <= 3);
+
+        switch (Mc) {
+                case 3: *ep++ = 0;
+                case 2:  do {
+                                *ep++ = 0;
+                case 1:         *ep++ = 0;
+                case 0:         *ep++ = *xMp++;
+                         } while (--i);
+        }
+        while (++Mc < 4) *ep++ = 0;
+
+	/*
+
+	int i, k;
+	for (k = 0; k <= 39; k++) ep[k] = 0;
+	for (i = 0; i <= 12; i++) {
+		ep[ Mc + (3*i) ] = xMp[i];
+	}
+	*/
+}
+
+/* 4.2.18 */
+
+/*  This procedure adds the reconstructed long term residual signal
+ *  ep[0..39] to the estimated signal dpp[0..39] from the long term
+ *  analysis filter to compute the reconstructed short term residual
+ *  signal dp[-40..-1]; also the reconstructed short term residual
+ *  array dp[-120..-41] is updated.
+ */
+
+#if 0	/* Has been inlined in code.c */
+void Gsm_Update_of_reconstructed_short_time_residual_signal P3((dpp, ep, dp),
+	word	* dpp,		/* [0...39]	IN	*/
+	word	* ep,		/* [0...39]	IN	*/
+	word	* dp)		/* [-120...-1]  IN/OUT 	*/
+{
+	int 		k;
+
+	for (k = 0; k <= 79; k++) 
+		dp[ -120 + k ] = dp[ -80 + k ];
+
+	for (k = 0; k <= 39; k++)
+		dp[ -40 + k ] = gsm_add( ep[k], dpp[k] );
+}
+#endif	/* Has been inlined in code.c */
+
+void Gsm_RPE_Encoding P5((S,e,xmaxc,Mc,xMc),
+
+	struct gsm_state * S,
+
+	word	* e,		/* -5..-1][0..39][40..44	IN/OUT  */
+	word	* xmaxc,	/* 				OUT */
+	word	* Mc,		/* 			  	OUT */
+	word	* xMc)		/* [0..12]			OUT */
+{
+	word	x[40];
+	word	xM[13], xMp[13];
+	word	mant, exp;
+
+	Weighting_filter(e, x);
+	RPE_grid_selection(x, xM, Mc);
+
+	APCM_quantization(	xM, xMc, &mant, &exp, xmaxc);
+	APCM_inverse_quantization(  xMc,  mant,  exp, xMp);
+
+	RPE_grid_positioning( *Mc, xMp, e );
+
+}
+
+void Gsm_RPE_Decoding P5((S, xmaxcr, Mcr, xMcr, erp),
+	struct gsm_state	* S,
+
+	word 		xmaxcr,
+	word		Mcr,
+	word		* xMcr,  /* [0..12], 3 bits 		IN	*/
+	word		* erp	 /* [0..39]			OUT 	*/
+)
+{
+	word	exp, mant;
+	word	xMp[ 13 ];
+
+	APCM_quantization_xmaxc_to_exp_mant( xmaxcr, &exp, &mant );
+	APCM_inverse_quantization( xMcr, mant, exp, xMp );
+	RPE_grid_positioning( Mcr, xMp, erp );
+
+}