--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/ietf_out.c	Thu May 09 07:06:31 2024 +0000
@@ -0,0 +1,57 @@
+/*
+ * The function implemented in this module is responsible for turning
+ * struct amr_param_frame (encoder output) into an RFC 4867 payload.
+ */
+
+#include <stdint.h>
+#include "tw_amr.h"
+#include "typedef.h"
+#include "namespace.h"
+#include "cnst.h"
+#include "int_defs.h"
+#include "if1_func.h"
+
+static const uint8_t total_bytes_per_ft[9] =
+		{13, 14, 16, 18, 20, 21, 27, 32, 6};
+
+static const uint8_t first_octet_per_ft[9] =
+		{0x04, 0x0C, 0x14, 0x1C, 0x24, 0x2C, 0x34, 0x3C, 0x44};
+
+unsigned amr_frame_to_ietf(const struct amr_param_frame *frame, uint8_t *bytes)
+{
+	Word16 serial[MAX_SERIAL_SIZE];
+	Word16 sti;
+	enum Mode ft;
+
+	switch (frame->type) {
+	case TX_SPEECH_GOOD:
+		ft = frame->mode;
+		break;
+	case TX_SID_FIRST:
+		ft = MRDTX;
+		sti = 0;
+		break;
+	case TX_SID_UPDATE:
+		ft = MRDTX;
+		sti = 1;
+		break;
+	case TX_NO_DATA:
+	default:
+		bytes[0] = 0x7C;
+		return 1;
+	}
+	Prm2bits(ft, frame->param, serial);
+	bytes[0] = first_octet_per_ft[ft];
+	if1_pack_bytes(ft, serial, bytes + 1);
+	if (ft == MRDTX) {
+		if (sti)
+			bytes[5] |= 0x10;
+		if (frame->mode & 1)
+			bytes[5] |= 0x08;
+		if (frame->mode & 2)
+			bytes[5] |= 0x04;
+		if (frame->mode & 4)
+			bytes[5] |= 0x02;
+	}
+	return total_bytes_per_ft[ft];
+}