--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Sat Nov 19 04:04:01 2022 +0000
@@ -0,0 +1,6 @@
+syntax: regexp
+
+\.[oa]$
+
+^dev/gsm0611-silence-fr$
+^dev/gsm0611-silence-fr\.out$

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dev/Makefile	Sat Nov 19 04:04:01 2022 +0000
@@ -0,0 +1,15 @@
+CC=	gcc
+CFLAGS=	-O2
+PROGS=	gsm0611-silence-fr
+DATAOUT=gsm0611-silence-fr.out
+
+all:	${PROGS} ${DATAOUT}
+
+gsm0611-silence-fr:	gsm0611-silence-fr.c
+	${CC} ${CFLAGS} -o $@ $@.c -lgsm
+
+gsm0611-silence-fr.out:	gsm0611-silence-fr
+	./gsm0611-silence-fr > $@
+
+clean:
+	rm -f *.o *.out ${PROGS}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dev/gsm0611-silence-fr.c	Sat Nov 19 04:04:01 2022 +0000
@@ -0,0 +1,49 @@
+/*
+ * This program is meant to be run only once by the developer - it uses
+ * libgsm function gsm_implode() to transform the idle frame of GSM 06.11
+ * (3GPP TS 46.011) from the table format given in the spec into
+ * libgsm/RTP format.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <gsm.h>
+
+static const gsm_signal lar_params[8] = {42, 39, 21, 10, 9, 4, 3, 2};
+static const gsm_signal subframe_params[17] =
+	{0, 40, 1, 0,  3, 4, 3, 4, 4,  3, 3, 3, 3, 4, 4, 3, 3};
+
+main(argc, argv)
+	char **argv;
+{
+	gsm state;
+	gsm_signal params[76];
+	gsm_byte frame[33];
+	unsigned n;
+
+	/* gsm_implode() requires dummy state */
+	state = gsm_create();
+	if (!state) {
+		fprintf(stderr, "gsm_create() failed!\n");
+		exit(1);
+	}
+	/* gather params */
+	bcopy(lar_params, params, sizeof(gsm_signal) * 8);
+	bcopy(subframe_params, params + 8, sizeof(gsm_signal) * 17);
+	bcopy(subframe_params, params + 25, sizeof(gsm_signal) * 17);
+	bcopy(subframe_params, params + 42, sizeof(gsm_signal) * 17);
+	bcopy(subframe_params, params + 59, sizeof(gsm_signal) * 17);
+	/* generate frame */
+	gsm_implode(state, params, frame);
+	/* print the frame */
+	for (n = 0; n < 33; n++) {
+		printf("0x%02X,", frame[n]);
+		if (n == 4 || n == 11 || n == 18 || n == 25 || n == 32)
+			putchar('\n');
+		else
+			putchar(' ');
+	}
+	exit(0);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmfrp/gsm_fr_preproc.h	Sat Nov 19 04:04:01 2022 +0000
@@ -0,0 +1,32 @@
+/*
+ * This header file is the external public interface to libgsmfrp;
+ * it should be installed in the same system include directory
+ * as <gsm.h> from libgsm, on which we depend.
+ */
+
+#ifndef	__GSM_FR_PREPROC_H
+#define	__GSM_FR_PREPROC_H
+
+#include <gsm.h>
+
+struct gsmfr_preproc_state;	/* opaque to external users */
+
+extern struct gsmfr_preproc_state *gsmfr_preproc_create(void);
+/* use standard free() call to free it afterward */
+
+/* reset state to initial */
+extern void gsmfr_preproc_reset(struct gsmfr_preproc_state *state);
+
+/* main processing functions */
+extern void gsmfr_preproc_good_frame(struct gsmfr_preproc_state *state,
+				     gsm_byte *frame);
+extern void gsmfr_preproc_bfi(struct gsmfr_preproc_state *state, int taf,
+			      gsm_byte *frame_out);
+
+/* utility function */
+extern int gsmfr_preproc_sid_classify(const gsm_frame *frame);
+
+/* utility datum */
+extern const gsm_frame gsmfr_preproc_silence_frame;
+
+#endif	/* include guard */

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmfrp/silence_frame.c	Sat Nov 19 04:04:01 2022 +0000
@@ -0,0 +1,15 @@
+/*
+ * Table 1 in section 6 of 3GPP TS 46.011 specifies a silence frame
+ * in the form of GSM 06.10 parameters; here we implement this exact
+ * silence frame in libgsm encoding, which is also RTP encoding.
+ */
+
+#include "gsm_fr_preproc.h"
+
+const gsm_frame gsmfr_preproc_silence_frame = {
+	0xDA, 0xA7, 0xAA, 0xA5, 0x1A,
+	0x00, 0x20, 0x38, 0xE4, 0x6D, 0xB9, 0x1B,
+	0x00, 0x20, 0x38, 0xE4, 0x6D, 0xB9, 0x1B,
+	0x00, 0x20, 0x38, 0xE4, 0x6D, 0xB9, 0x1B,
+	0x00, 0x20, 0x38, 0xE4, 0x6D, 0xB9, 0x1B,
+};