--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/ietf_in.c	Thu May 09 07:06:31 2024 +0000
@@ -0,0 +1,49 @@
+/*
+ * The function implemented in this module is responsible for parsing
+ * an incoming RFC 4867 payload and turning it into struct amr_param_frame
+ * for decoding.
+ */
+
+#include <stdint.h>
+#include "tw_amr.h"
+#include "typedef.h"
+#include "namespace.h"
+#include "cnst.h"
+#include "int_defs.h"
+#include "if1_func.h"
+
+int amr_frame_from_ietf(const uint8_t *bytes, struct amr_param_frame *frame)
+{
+	Word16 ft, q, sti;
+	Word16 serial[MAX_SERIAL_SIZE];
+
+	ft = (bytes[0] & 0x78) >> 3;
+	q  = (bytes[0] & 0x04) >> 2;
+	if (ft == AMR_FT_NODATA) {
+		frame->type = RX_NO_DATA;
+		frame->mode = 0xFF;
+		return 0;
+	}
+	if (ft > MRDTX)
+		return -1;
+	if1_unpack_bytes(ft, bytes + 1, serial);
+	Bits2prm(ft, serial, frame->param);
+	if (ft != MRDTX) {
+		frame->type = q ? RX_SPEECH_GOOD : RX_SPEECH_BAD;
+		frame->mode = ft;
+	} else {
+		sti = (bytes[5] & 0x10) >> 4;
+		frame->mode = 0;
+		if (bytes[5] & 0x08)
+			frame->mode |= 1;
+		if (bytes[5] & 0x04)
+			frame->mode |= 2;
+		if (bytes[5] & 0x02)
+			frame->mode |= 4;
+		if (q)
+			frame->type = sti ? RX_SID_UPDATE : RX_SID_FIRST;
+		else
+			frame->type = RX_SID_BAD;
+	}
+	return 0;
+}