--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmefr/dec_rtp_in.c	Sat Sep 28 06:38:08 2024 +0000
@@ -0,0 +1,47 @@
+/*
+ * This module implements a wrapper around the main processing functions
+ * of our full decoder, handling RTP input per TW-TS-001.
+ */
+
+#include <stdint.h>
+#include "gsm_efr.h"
+
+int EFR_decode_rtp(struct EFR_decoder_state *st, const uint8_t *rtp_pl,
+		   unsigned rtp_pl_len, int16_t *pcm)
+{
+	switch (rtp_pl_len) {
+	case 0:
+		/* BFI-no-data, but not an invalid RTP input per se */
+		EFR_decode_bfi_nodata(st, 0, pcm);
+		return 0;
+	case 1:
+		if ((rtp_pl[0] & 0xF6) != 0xE6)
+			goto bad_rtp_input;
+		/* TW-TS-001 No_Data frame */
+		EFR_decode_bfi_nodata(st, rtp_pl[0] & 1, pcm);
+		return 0;
+	case EFR_RTP_FRAME_LEN:
+		if ((rtp_pl[0] & 0xF0) != 0xC0)
+			goto bad_rtp_input;
+		/* basic RTP format */
+		EFR_decode_frame(st, rtp_pl, 0, 0, pcm);
+		return 0;
+	case EFR_RTP_FRAME_LEN+1:
+		if ((rtp_pl[0] & 0xF4) != 0xE0)
+			goto bad_rtp_input;
+		if ((rtp_pl[1] & 0xF0) != 0xC0)
+			goto bad_rtp_input;
+		/* extended RTP format (TW-TS-001) */
+		EFR_decode_frame(st, rtp_pl + 1, (rtp_pl[0] & 2) >> 1,
+				 rtp_pl[0] & 1, pcm);
+		return 0;
+	default:
+	bad_rtp_input:
+		/*
+		 * Treat it like BFI-no-data, and tell the caller
+		 * that we received an invalid RTP payload.
+		 */
+		EFR_decode_bfi_nodata(st, 0, pcm);
+		return -1;
+	}
+}