--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/frtest/dlcap-gsmx.c	Fri Dec 16 04:09:03 2022 +0000
@@ -0,0 +1,78 @@
+/*
+ * This program reads a TCH/FS downlink capture produced with FreeCalypso tools
+ * (fw version with TCH downlink sniffing feature and fc-shell tch record)
+ * and converts it into our extended-libgsm binary format, to be further
+ * fed to gsmfr-decode.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+main(argc, argv)
+	char **argv;
+{
+	FILE *inf, *outf;
+	char linebuf[128];
+	int lineno, rc;
+	uint16_t status_words[3];
+	uint8_t tidsp_bytes[33], libgsm_bytes[33], bfi[2];
+	unsigned fn_mod_104;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: %s infile outfile\n", argv[0]);
+		exit(1);
+	}
+	inf = fopen(argv[1], "r");
+	if (!inf) {
+		perror(argv[1]);
+		exit(1);
+	}
+	outf = fopen(argv[2], "w");
+	if (!outf) {
+		perror(argv[2]);
+		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;
+		/*
+		 * Bit 15 of status word 0 is buffer validity flag,
+		 * bit 2 is BFI.
+		 */
+		if (!(status_words[0] & 0x8000) || (status_words[0] & 0x0004)) {
+			bfi[0] = 0xBF;
+			bfi[1] = fn_mod_104 == 60;
+			fwrite(bfi, 1, 2, outf);
+		} else {
+			gsm0610_tidsp_to_libgsm(tidsp_bytes, libgsm_bytes);
+			fwrite(libgsm_bytes, 1, 33, outf);
+		}
+	}
+	exit(0);
+}