diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index cd0e8b0b3..1d975ea74 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -386,7 +386,7 @@ srs_error_t SrsDtlsSession::protect_rtp(char* out_buf, const char* in_buf, int&
     return srs_error_new(ERROR_RTC_SRTP_PROTECT, "rtp protect failed");
 }
 
-srs_error_t SrsDtlsSession::protect_rtp2(char* buf, int* pnn_buf, SrsRtpPacket2* pkt)
+srs_error_t SrsDtlsSession::protect_rtp2(void* rtp_hdr, int* len_ptr)
 {
     srs_error_t err = srs_success;
 
@@ -394,14 +394,7 @@ srs_error_t SrsDtlsSession::protect_rtp2(char* buf, int* pnn_buf, SrsRtpPacket2*
         return srs_error_new(ERROR_RTC_SRTP_PROTECT, "rtp protect");
     }
 
-    SrsBuffer stream(buf, *pnn_buf);
-    if ((err = pkt->encode(&stream)) != srs_success) {
-        return srs_error_wrap(err, "encode packet");
-    }
-
-    *pnn_buf = stream.pos();
-
-    if (srtp_protect(srtp_send, buf, pnn_buf) != 0) {
+    if (srtp_protect(srtp_send, rtp_hdr, len_ptr) != 0) {
         return srs_error_new(ERROR_RTC_SRTP_PROTECT, "rtp protect");
     }
 
@@ -587,14 +580,15 @@ srs_error_t SrsRtcSenderThread::cycle()
             continue;
         }
 
-        int nn = 0;
         int nn_rtp_pkts = 0;
-        if ((err = send_messages(source, msgs.msgs, msg_count, sendonly_ukt, &nn, &nn_rtp_pkts)) != srs_success) {
+        if ((err = send_messages(source, msgs.msgs, msg_count, sendonly_ukt, &nn_rtp_pkts)) != srs_success) {
             srs_warn("send err %s", srs_error_summary(err).c_str()); srs_error_reset(err);
         }
 
+        int nn = 0;
         for (int i = 0; i < msg_count; i++) {
             SrsSharedPtrMessage* msg = msgs.msgs[i];
+            nn += msg->size;
             srs_freep(msg);
         }
 
@@ -608,7 +602,7 @@ srs_error_t SrsRtcSenderThread::cycle()
 
 srs_error_t SrsRtcSenderThread::send_messages(
     SrsSource* source, SrsSharedPtrMessage** msgs, int nb_msgs,
-    SrsUdpMuxSocket* skt, int* pnn, int* pnn_rtp_pkts
+    SrsUdpMuxSocket* skt, int* pnn_rtp_pkts
 ) {
     srs_error_t err = srs_success;
 
@@ -618,10 +612,34 @@ srs_error_t SrsRtcSenderThread::send_messages(
 
     // Covert kernel messages to RTP packets.
     vector<SrsRtpPacket2*> packets;
+    if ((err = messages_to_packets(source, msgs, nb_msgs, packets)) != srs_success) {
+        for (int j = 0; j < (int)packets.size(); j++) {
+            SrsRtpPacket2* packet = packets[j];
+            srs_freep(packet);
+        }
+        return err;
+    }
+
+    *pnn_rtp_pkts += (int)packets.size();
+
+    for (int j = 0; j < (int)packets.size(); j++) {
+        SrsRtpPacket2* packet = packets[j];
+        if ((err = send_packet(packet, skt)) != srs_success) {
+            srs_warn("send err %s", srs_error_summary(err).c_str()); srs_error_reset(err);
+        }
+        srs_freep(packet);
+    }
+
+    return err;
+}
+
+srs_error_t SrsRtcSenderThread::messages_to_packets(
+    SrsSource* source, SrsSharedPtrMessage** msgs, int nb_msgs, vector<SrsRtpPacket2*>& packets
+) {
+    srs_error_t err = srs_success;
 
     for (int i = 0; i < nb_msgs; i++) {
         SrsSharedPtrMessage* msg = msgs[i];
-        *pnn += msg->size;
 
         SrsRtpPacket2* packet = NULL;
         if (msg->is_audio()) {
@@ -632,7 +650,6 @@ srs_error_t SrsRtcSenderThread::send_messages(
                 }
                 packets.push_back(packet);
             }
-
             continue;
         }
 
@@ -675,16 +692,6 @@ srs_error_t SrsRtcSenderThread::send_messages(
         }
     }
 
-    *pnn_rtp_pkts += (int)packets.size();
-
-    for (int j = 0; j < (int)packets.size(); j++) {
-        SrsRtpPacket2* packet = packets[j];
-        if ((err = send_packet(packet, skt)) != srs_success) {
-            srs_warn("send err %s", srs_error_summary(err).c_str()); srs_error_reset(err);
-        }
-        srs_freep(packet);
-    }
-
     return err;
 }
 
@@ -701,15 +708,10 @@ srs_error_t SrsRtcSenderThread::send_packet(SrsRtpPacket2* pkt, SrsUdpMuxSocket*
         return srs_error_wrap(err, "fetch msghdr");
     }
     char* buf = (char*)mhdr->msg_hdr.msg_iov->iov_base;
-
-    // Length of iov, default size.
     int length = kRtpPacketSize;
 
-    if (rtc_session->encrypt) {
-        if ((err = rtc_session->dtls_session->protect_rtp2(buf, &length, pkt)) != srs_success) {
-            return srs_error_wrap(err, "srtp protect");
-        }
-    } else {
+    // Marshal packet to bytes.
+    if (true) {
         SrsBuffer stream(buf, length);
         if ((err = pkt->encode(&stream)) != srs_success) {
             return srs_error_wrap(err, "encode packet");
@@ -717,6 +719,13 @@ srs_error_t SrsRtcSenderThread::send_packet(SrsRtpPacket2* pkt, SrsUdpMuxSocket*
         length = stream.pos();
     }
 
+    // Whether encrypt the RTP bytes.
+    if (rtc_session->encrypt) {
+        if ((err = rtc_session->dtls_session->protect_rtp2(buf, &length)) != srs_success) {
+            return srs_error_wrap(err, "srtp protect");
+        }
+    }
+
     sockaddr_in* addr = (sockaddr_in*)skt->peer_addr();
     socklen_t addrlen = (socklen_t)skt->peer_addrlen();
 
diff --git a/trunk/src/app/srs_app_rtc_conn.hpp b/trunk/src/app/srs_app_rtc_conn.hpp
index 3fef015c6..a0c370942 100644
--- a/trunk/src/app/srs_app_rtc_conn.hpp
+++ b/trunk/src/app/srs_app_rtc_conn.hpp
@@ -105,7 +105,7 @@ public:
     srs_error_t on_dtls_application_data(const char* data, const int len);
 public:
     srs_error_t protect_rtp(char* protected_buf, const char* ori_buf, int& nb_protected_buf);
-    srs_error_t protect_rtp2(char* buf, int* pnn_buf, SrsRtpPacket2* pkt);
+    srs_error_t protect_rtp2(void* rtp_hdr, int* len_ptr);
     srs_error_t unprotect_rtp(char* unprotected_buf, const char* ori_buf, int& nb_unprotected_buf);
     srs_error_t protect_rtcp(char* protected_buf, const char* ori_buf, int& nb_protected_buf);
     srs_error_t unprotect_rtcp(char* unprotected_buf, const char* ori_buf, int& nb_unprotected_buf);
@@ -152,7 +152,8 @@ public:
 public:
     virtual srs_error_t cycle();
 private:
-    srs_error_t send_messages(SrsSource* source, SrsSharedPtrMessage** msgs, int nb_msgs, SrsUdpMuxSocket* skt, int* pnn, int* pnn_rtp_pkts);
+    srs_error_t send_messages(SrsSource* source, SrsSharedPtrMessage** msgs, int nb_msgs, SrsUdpMuxSocket* skt, int* pnn_rtp_pkts);
+    srs_error_t messages_to_packets(SrsSource* source, SrsSharedPtrMessage** msgs, int nb_msgs, std::vector<SrsRtpPacket2*>& packets);
     srs_error_t send_packet(SrsRtpPacket2* pkt, SrsUdpMuxSocket* skt);
 private:
     srs_error_t packet_opus(SrsSample* sample, SrsRtpPacket2** ppacket);