--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dev/pack_gsmfr_rtp.c	Sun Apr 14 03:38:09 2024 +0000
@@ -0,0 +1,57 @@
+/*
+ * The function in this development-only module is a copy of
+ * gsmfr_pack_from_array() from work-in-progress libgsmfr2, which in turn
+ * was created to serve as a drop-in replacement for gsm_implode()
+ * from classic libgsm.  The function is copied here to avoid the
+ * philosophical problem of libgsmfr2 being a dependency for developer aid
+ * programs used in the development of that library.
+ */
+
+#include <stdint.h>
+
+#define	GSM_FR_MAGIC	0xD
+
+void gsmfr_pack_to_rtp(const int16_t *params, uint8_t *frame)
+{
+	uint8_t *c = frame;
+	unsigned sub;
+
+	*c++ =   (GSM_FR_MAGIC << 4)
+	       | ((params[0] >> 2) & 0xF);
+	*c++ =   ((params[0] & 0x3) << 6)
+	       | (params[1] & 0x3F);
+	*c++ =   ((params[2] & 0x1F) << 3)
+	       | ((params[3] >> 2) & 0x7);
+	*c++ =   ((params[3] & 0x3) << 6)
+	       | ((params[4] & 0xF) << 2)
+	       | ((params[5] >> 2) & 0x3);
+	*c++ =   ((params[5] & 0x3) << 6)
+	       | ((params[6] & 0x7) << 3)
+	       | (params[7] & 0x7);
+	params += 8;
+	for (sub = 0; sub < 4; sub++) {
+		*c++ =   ((params[0] & 0x7F) << 1)
+		       | ((params[1] >> 1) & 0x1);
+		*c++ =   ((params[1] & 0x1) << 7)
+		       | ((params[2] & 0x3) << 5)
+		       | ((params[3] >> 1) & 0x1F);
+		*c++ =   ((params[3] & 0x1) << 7)
+		       | ((params[4] & 0x7) << 4)
+		       | ((params[5] & 0x7) << 1)
+		       | ((params[6] >> 2) & 0x1);
+		*c++ =   ((params[6] & 0x3) << 6)
+		       | ((params[7] & 0x7) << 3)
+		       | (params[8] & 0x7);
+		*c++ =   ((params[9] & 0x7) << 5)
+		       | ((params[10] & 0x7) << 2)
+		       | ((params[11] >> 1) & 0x3);
+		*c++ =   ((params[11] & 0x1) << 7)
+		       | ((params[12] & 0x7) << 4)
+		       | ((params[13] & 0x7) << 1)
+		       | ((params[14] >> 2) & 0x1);
+		*c++ =   ((params[14] & 0x3) << 6)
+		       | ((params[15] & 0x7) << 3)
+		       | (params[16] & 0x7);
+		params += 17;
+	}
+}