--- res/res_srtp.c	(Asterisk 13.38.3)
+++ res/res_srtp.c	2021-03-10 10:55:00.767873340 +0100
@@ -478,6 +478,19 @@ static int ast_srtp_protect(struct ast_s
 		return -1;
 	}
 
+	if (!rtcp) {
+		uint32_t roc;
+		struct ast_rtp_engine *engine = ast_rtp_instance_get_engine(srtp->rtp);
+		unsigned int local_ssrc = engine->ssrc(srtp->rtp);
+		srtp_err_status_t error = srtp_get_stream_roc(srtp->session, local_ssrc, &roc);		
+		if (!error && roc) {
+			unsigned short seqno = engine->seqno(srtp->rtp);
+			if (100 < seqno && seqno < 300) { // 2 sec wait, 4 sec break
+				localbuf[*len - 3] = 0x00;
+			}
+		}
+	}
+
 	*buf = localbuf;
 	return *len;
 }
--- res/res_rtp_asterisk.c	(Asterisk 13.38.3)
+++ res/res_rtp_asterisk.c	2021-03-10 10:55:00.767873340 +0100
@@ -529,2 +529,4 @@ static void ast_rtp_stun_request(struct
 static int ast_rtp_qos_set(struct ast_rtp_instance *instance, int tos, int cos, const char* desc);
+static unsigned short ast_rtp_seqno(struct ast_rtp_instance *instance);
+static unsigned int ast_rtp_ssrc(struct ast_rtp_instance *instance);
 static int ast_rtp_sendcng(struct ast_rtp_instance *instance, int level);
@@ -2095,2 +2097,4 @@ static struct ast_rtp_engine asterisk_rt
 	.qos = ast_rtp_qos_set,
+	.ssrc = ast_rtp_ssrc,
+	.seqno = ast_rtp_seqno,
 	.sendcng = ast_rtp_sendcng,
@@ -3345,1 +3349,1 @@ static int ast_rtp_new(struct ast_rtp_in
-	rtp->seqno = ast_random() & 0x7fff;
+	rtp->seqno = 0xffff - 100;
@@ -6487,6 +6491,18 @@ static int ast_rtp_qos_set(struct a
 	return ast_set_qos(rtp->s, tos, cos, desc);
 }
 
+static unsigned short ast_rtp_seqno(struct ast_rtp_instance *instance)
+{
+	struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
+	return rtp->seqno;
+}
+
+static unsigned int ast_rtp_ssrc(struct ast_rtp_instance *instance)
+{
+	struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
+	return rtp->ssrc;
+}
+
 /*!
  * \brief generate comfort noice (CNG)
  *
--- include/asterisk/rtp_engine.h	(Asterisk 13.38.3)
+++ include/asterisk/rtp_engine.h	2021-03-10 10:55:00.767873340 +0100
@@ -591,2 +591,4 @@ struct ast_rtp_engine {
 	void (*available_formats)(struct ast_rtp_instance *instance, struct ast_format_cap *to_endpoint, struct ast_format_cap *to_asterisk, struct ast_format_cap *result);
+	unsigned short (*seqno)(struct ast_rtp_instance *instance);
+	unsigned int (*ssrc)(struct ast_rtp_instance *instance);
 	/*! Callback to send CNG */