--- a/.hgignore	Fri Dec 16 08:23:32 2022 +0000
+++ b/.hgignore	Fri Dec 16 08:38:36 2022 +0000
@@ -27,6 +27,7 @@
 ^frtest/gsmfr-decode$
 ^frtest/gsmfr-decode-r$
 ^frtest/gsmfr-dlcap-gsmx$
+^frtest/gsmfr-dlcap-parse$
 ^frtest/gsmfr-encode$
 ^frtest/gsmfr-encode-r$
 ^frtest/gsmfr-hand-test$

--- a/frtest/Makefile	Fri Dec 16 08:23:32 2022 +0000
+++ b/frtest/Makefile	Fri Dec 16 08:38:36 2022 +0000
@@ -1,7 +1,7 @@
 CC=	gcc
 CFLAGS=	-O2
-PROGS=	gsmfr-decode gsmfr-decode-r gsmfr-dlcap-gsmx gsmfr-encode \
-	gsmfr-encode-r gsmfr-hand-test gsmfr-max-out gsmfr-preproc
+PROGS=	gsmfr-decode gsmfr-decode-r gsmfr-dlcap-gsmx gsmfr-dlcap-parse \
+	gsmfr-encode gsmfr-encode-r gsmfr-hand-test gsmfr-max-out gsmfr-preproc
 LIBPP=	../libgsmfrp/libgsmfrp.a
 LIBTEST=../libtest/libtest.a
 LIBDEC=	${LIBTEST} ${LIBPP}
@@ -18,6 +18,9 @@
 gsmfr-dlcap-gsmx:	dlcap-gsmx.o tidsp.o ${LIBTEST}
 	${CC} ${CFLAGS} -o $@ dlcap-gsmx.o tidsp.o ${LIBTEST}
 
+gsmfr-dlcap-parse:	dlcap-parse.o tidsp.o ${LIBDEC}
+	${CC} ${CFLAGS} -o $@ dlcap-parse.o tidsp.o ${LIBDEC} -lgsm
+
 gsmfr-encode:	encode.o ${LIBTEST}
 	${CC} ${CFLAGS} -o $@ encode.o ${LIBTEST} -lgsm
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/frtest/dlcap-parse.c	Fri Dec 16 08:38:36 2022 +0000
@@ -0,0 +1,104 @@
+/*
+ * This program reads a TCH/FS downlink capture produced with FreeCalypso tools
+ * (fw version with TCH downlink sniffing feature and fc-shell tch record),
+ * parses the frame bits according to our current understanding, and dumps
+ * everything in human-readable form for further analysis.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <gsm.h>
+#include "../libgsmfrp/gsm_fr_preproc.h"
+
+static void
+process_record(lineno, fn_mod_104, status_words, tidsp_bytes, dummy_state)
+	int lineno;
+	unsigned fn_mod_104;
+	uint16_t *status_words;
+	uint8_t *tidsp_bytes;
+	gsm dummy_state;
+{
+	uint8_t libgsm_bytes[33];
+	int16_t params[76];
+	int i, j, n;
+
+	printf("#%d: fn=%u DSP %04X %04X %04X\n", lineno, fn_mod_104,
+		status_words[0], status_words[1], status_words[2]);
+	gsm0610_tidsp_to_libgsm(tidsp_bytes, libgsm_bytes);
+	fputs("  bits ", stdout);
+	for (i = 0; i < 33; i++)
+		printf("%02X", tidsp_bytes[i]);
+	printf(" SID=%d\n", gsmfr_preproc_sid_classify(libgsm_bytes));
+	gsm_explode(dummy_state, libgsm_bytes, params);
+	fputs("  FR", stdout);
+	n = 0;
+	for (i = 0; i < 8; i++)
+		printf(" %d", params[n++]);
+	putchar('\n');
+	for (i = 0; i < 4; i++) {
+		putchar(' ');
+		for (j = 0; j < 17; j++)
+			printf(" %d", params[n++]);
+		putchar('\n');
+	}
+}
+
+main(argc, argv)
+	char **argv;
+{
+	FILE *inf;
+	gsm dummy_state;
+	char linebuf[128];
+	int lineno, rc;
+	uint16_t status_words[3];
+	uint8_t tidsp_bytes[33];
+	unsigned fn_mod_104;
+
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s dlcap-file\n", argv[0]);
+		exit(1);
+	}
+	inf = fopen(argv[1], "r");
+	if (!inf) {
+		perror(argv[1]);
+		exit(1);
+	}
+	dummy_state = gsm_create();
+	if (!dummy_state) {
+		fprintf(stderr, "gsm_create() failed!\n");
+		exit(1);
+	}
+	for (lineno = 1; fgets(linebuf, sizeof linebuf, inf); lineno++) {
+		/* support both old and new formats */
+		if (isxdigit(linebuf[0]) && isxdigit(linebuf[1]) &&
+		    isxdigit(linebuf[2]) && isxdigit(linebuf[3])) {
+			rc = parse_dlcap_common(linebuf, status_words,
+						tidsp_bytes);
+			if (rc < 0) {
+invalid:			fprintf(stderr,
+				"error: %s is not in the expected format\n",
+					argv[1]);
+				exit(1);
+			}
+			fn_mod_104 = 0;		/* won't have TAF */
+		} else if (!strncmp(linebuf, "FR ", 3)) {
+			rc = parse_dlcap_common(linebuf + 3, status_words,
+						tidsp_bytes);
+			if (rc < 0)
+				goto invalid;
+			if (linebuf[84] != ' ')
+				goto invalid;
+			if (!isdigit(linebuf[85]))
+				goto invalid;
+			fn_mod_104 = strtoul(linebuf + 85, 0, 10);
+		} else
+			goto invalid;
+		process_record(lineno, fn_mod_104, status_words, tidsp_bytes,
+				dummy_state);
+	}
+	exit(0);
+}