diff --git a/trunk/src/app/srs_app_rtp_queue.cpp b/trunk/src/app/srs_app_rtp_queue.cpp
index bfed41778..28637e738 100644
--- a/trunk/src/app/srs_app_rtp_queue.cpp
+++ b/trunk/src/app/srs_app_rtp_queue.cpp
@@ -134,20 +134,123 @@ void SrsRtpNackList::update_rtt(int rtt)
     opts_.nack_interval = rtt_;
 }
 
-SrsRtpQueue::SrsRtpQueue(size_t capacity, bool one_packet_per_frame)
-    : nack_(this, capacity * 2 / 3)
+SrsRtpRingBuffer::SrsRtpRingBuffer(size_t capacity)
 {
+    nn_seq_flip_backs = 0;
+    high_ = low_ = 0;
     capacity_ = capacity;
-    head_sequence_ = 0;
-    highest_sequence_ = 0;
     initialized_ = false;
-    start_collected_ = false;
+
     queue_ = new SrsRtpSharedPacket*[capacity_];
     memset(queue_, 0, sizeof(SrsRtpSharedPacket*) * capacity);
+}
+
+SrsRtpRingBuffer::~SrsRtpRingBuffer()
+{
+    srs_freepa(queue_);
+}
+
+void SrsRtpRingBuffer::set(uint16_t at, SrsRtpSharedPacket* pkt)
+{
+    SrsRtpSharedPacket* p = queue_[at % capacity_];
+
+    if (p) {
+        srs_freep(p);
+    }
+
+    queue_[at % capacity_] = pkt;
+}
+
+void SrsRtpRingBuffer::remove(uint16_t at)
+{
+    set(at, NULL);
+}
+
+uint16_t SrsRtpRingBuffer::next_start_of_frame()
+{
+    if (low_ == high_) {
+        return low_;
+    }
+
+    for (uint16_t s = low_ + 1 ; s != high_; ++s) {
+        SrsRtpSharedPacket*& pkt = queue_[s % capacity_];
+        if (pkt && pkt->rtp_payload_header->is_first_packet_of_frame) {
+            return s;
+        }
+    }
+
+    return low_;
+}
+
+uint16_t SrsRtpRingBuffer::next_keyframe()
+{
+    if (low_ == high_) {
+        return low_;
+    }
+
+    for (uint16_t s = low_ + 1 ; s != high_; ++s) {
+        SrsRtpSharedPacket*& pkt = queue_[s % capacity_];
+        if (pkt && pkt->rtp_payload_header->is_key_frame && pkt->rtp_payload_header->is_first_packet_of_frame) {
+            return s;
+        }
+    }
+
+    return low_;
+}
+
+uint32_t SrsRtpRingBuffer::get_extended_highest_sequence()
+{
+    return nn_seq_flip_backs * 65536 + high_;
+}
+
+void SrsRtpRingBuffer::update(uint16_t seq, bool startup, uint16_t& nack_low, uint16_t& nack_high)
+{
+    if (!initialized_) {
+        initialized_ = true;
+        low_ = high_ = seq;
+        return;
+    }
+
+    // Normal sequence, seq follows high_.
+    if (srs_rtp_seq_distance(high_, seq)) {
+        nack_low = high_ + 1;
+        nack_high = seq;
+
+        // When distance(seq,high_)>0 and seq<high_, seq must flip back,
+        // for example, high_=65535, seq=1, distance(65535,1)>0 and 1<65535.
+        if (seq < high_) {
+            srs_verbose("warp around, flip_back=%" PRId64, nn_seq_flip_backs);
+            ++nn_seq_flip_backs;
+        }
+        high_ = seq;
+        return;
+    }
+
+    // Out-of-order sequence, seq before low_.
+    if (srs_rtp_seq_distance(seq, low_)) {
+        // When startup, we may receive packets in chaos order.
+        // Because we don't know the ISN(initiazlie sequence number), the first packet
+        // we received maybe no the first packet client sent.
+        if (startup) {
+            nack_low = seq + 1;
+            nack_high = low_;
+
+            srs_info("head seq=%u, cur seq=%u, update head seq because recv less than it.", low_, seq);
+            low_ = seq;
+        } else {
+            srs_verbose("seq=%u, rtx success, too old", seq);
+        }
+    }
+}
+
+SrsRtpQueue::SrsRtpQueue(size_t capacity, bool one_packet_per_frame)
+    : nack_(this, capacity * 2 / 3)
+{
+    nn_collected_frames = 0;
+    queue_ = new SrsRtpRingBuffer(capacity);
 
-    cycle_ = 0;
     jitter_ = 0;
-    last_trans_time_ = 0;
+    last_trans_time_ = -1;
     
     pre_number_of_packet_received_ = 0;
     pre_number_of_packet_lossed_ = 0;
@@ -162,137 +265,91 @@ SrsRtpQueue::SrsRtpQueue(size_t capacity, bool one_packet_per_frame)
 
 SrsRtpQueue::~SrsRtpQueue()
 {
-    srs_freepa(queue_);
+    srs_freep(queue_);
 }
 
 srs_error_t SrsRtpQueue::insert(SrsRtpSharedPacket* rtp_pkt)
 {
     srs_error_t err = srs_success;
 
-    uint16_t seq = rtp_pkt->rtp_header.get_sequence();
-
     // TODO: FIXME: Update time for each packet, may hurt performance.
     srs_utime_t now = srs_update_system_time();
 
-    // First packet recv, init head_sequence and highest_sequence.
-    if (!initialized_) {
-        initialized_ = true;
-        head_sequence_ = seq;
-        highest_sequence_ = seq;
+    uint16_t seq = rtp_pkt->rtp_header.get_sequence();
+    SrsRtpNackInfo* nack_info = nack_.find(seq);
+    if (nack_info) {
+        int nack_rtt = nack_info->req_nack_count_ ? ((now - nack_info->pre_req_nack_time_) / SRS_UTIME_MILLISECONDS) : 0;
+        (void)nack_rtt;
+        srs_verbose("seq=%u, alive time=%d, nack count=%d, rtx success, resend use %dms",
+            seq, now - nack_info->generate_time_, nack_info->req_nack_count_, nack_rtt);
+        nack_.remove(seq);
+    }
 
-        ++num_of_packet_received_;
+    // Calc jitter time, ignore nack packets.
+    // TODO: FIXME: Covert time to srs_utime_t.
+    if (last_trans_time_ == -1) {
+        last_trans_time_ = now / 1000 - rtp_pkt->rtp_header.get_timestamp() / 90;
+    } else if (!nack_info) {
+        int trans_time = now / 1000 - rtp_pkt->rtp_header.get_timestamp() / 90;
 
-        // TODO: FIXME: Covert time to srs_utime_t.
-        last_trans_time_ = now/1000 - rtp_pkt->rtp_header.get_timestamp()/90;
-    } else {
-        SrsRtpNackInfo* nack_info = NULL;
-        if ((nack_info = nack_.find(seq)) != NULL) {
-            int nack_rtt = nack_info->req_nack_count_ ? ((now - nack_info->pre_req_nack_time_) / SRS_UTIME_MILLISECONDS) : 0;
-            (void)nack_rtt;
-            srs_verbose("seq=%u, alive time=%d, nack count=%d, rtx success, resend use %dms", 
-                seq, now - nack_info->generate_time_, nack_info->req_nack_count_, nack_rtt);
-            nack_.remove(seq);
-        } else {
-            // Calc jitter.
-            {
-                int trans_time = now / 1000 - rtp_pkt->rtp_header.get_timestamp() / 90;
-
-                int cur_jitter = trans_time - last_trans_time_;
-                if (cur_jitter < 0) {
-                    cur_jitter = -cur_jitter;
-                }
-
-                last_trans_time_ = trans_time;
-
-                jitter_ = (jitter_ * 15.0 / 16.0) + (static_cast<double>(cur_jitter) / 16.0);
-                srs_verbose("jitter=%.2f", jitter_);
-            }
-
-            ++num_of_packet_received_;
-            // seq > highest_sequence_
-            if (seq_cmp(highest_sequence_, seq)) {
-                insert_into_nack_list(highest_sequence_ + 1, seq);
-
-                if (seq < highest_sequence_) {
-                    srs_verbose("warp around, cycle=%lu", cycle_);
-                    ++cycle_;
-                }
-                highest_sequence_ = seq;
-            } else {
-                // Because we don't know the ISN(initiazlie sequence number), the first packet
-                // we received maybe no the first packet client sented.
-                if (!start_collected_) {
-                    if (seq_cmp(seq, head_sequence_)) {
-                        srs_info("head seq=%u, cur seq=%u, update head seq because recv less than it.", head_sequence_, seq);
-                        head_sequence_ = seq;
-                    }
-                    insert_into_nack_list(seq + 1, highest_sequence_);
-                } else {
-                    srs_verbose("seq=%u, rtx success, too old", seq);
-                }
-            }
+        int cur_jitter = trans_time - last_trans_time_;
+        if (cur_jitter < 0) {
+            cur_jitter = -cur_jitter;
         }
+
+        last_trans_time_ = trans_time;
+
+        jitter_ = (jitter_ * 15.0 / 16.0) + (static_cast<double>(cur_jitter) / 16.0);
+        srs_verbose("jitter=%.2f", jitter_);
     }
 
-    // Check seqs out of range.
-    if (head_sequence_ + capacity_ < highest_sequence_) {
+    // OK, we got one new RTP packet, which is not in NACK.
+    if (!nack_info) {
+        ++num_of_packet_received_;
+        uint16_t nack_low = 0, nack_high = 0;
+        queue_->update(seq, !nn_collected_frames, nack_low, nack_high);
+        if (srs_rtp_seq_distance(nack_low, nack_high)) {
+            srs_trace("update nack seq=%u, startup=%d, nack range [%u, %u]", seq, !nn_collected_frames, nack_low, nack_high);
+            insert_into_nack_list(nack_low, nack_high);
+        }
+    }
+
+    // When packets overflow, collect frame and move head to next frame start.
+    if (queue_->overflow()) {
         srs_verbose("try collect packet becuase seq out of range");
         collect_packet();
-    }
-    while (head_sequence_ + capacity_ < highest_sequence_) {
-        srs_trace("seqs out of range, head seq=%u, hightest seq=%u", head_sequence_, highest_sequence_);
-        remove(head_sequence_);
-        uint16_t s = head_sequence_ + 1;
-        for ( ; s != highest_sequence_; ++s) {
-            SrsRtpSharedPacket*& pkt = queue_[s % capacity_];
-            // Choose the new head sequence. Must be the first packet of frame.
-            if (pkt && pkt->rtp_payload_header->is_first_packet_of_frame) {
-                srs_trace("find except, update head seq from %u to %u when seqs out of range", head_sequence_, s);
-                head_sequence_ = s;
-                break;
-            }
-
-            // Drop the seq.
+
+        uint16_t next = queue_->next_start_of_frame();
+
+        // Note that low_ mean not found, clear queue util one packet.
+        if (next == queue_->low()) {
+            next = queue_->high() - 1;
+        }
+        srs_trace("seqs out of range, seq range [%u, %u]", queue_->low(), next);
+
+        for (uint16_t s = queue_->low(); s != next; ++s) {
             nack_.remove(s);
-            srs_verbose("seqs out of range, drop seq=%u", s);
-            if (pkt && pkt->rtp_header.get_sequence() == s) {
-                delete pkt;
-                pkt = NULL;
-            }
+            queue_->remove(s);
         }
-        srs_trace("force update, update head seq from %u to %u when seqs out of range", head_sequence_, s);
-        head_sequence_ = s;
-    }
 
-    SrsRtpSharedPacket*& old_pkt = queue_[seq % capacity_];
-    if (old_pkt) {
-        delete old_pkt;
+        srs_trace("force update, update head seq from %u to %u when seqs out of range", queue_->low(), next + 1);
+        queue_->advance_to(next + 1);
     }
 
     // TODO: FIXME: Change to ptr of ptr.
-    old_pkt = rtp_pkt->copy();
+    queue_->set(seq, rtp_pkt->copy());
 
-    // Marker bit means the last packet of frame received.
-    if (rtp_pkt->rtp_header.get_marker() || (highest_sequence_ - head_sequence_ >= capacity_ / 2) || one_packet_per_frame_) {
+    // Collect packets to frame when:
+    // 1. Marker bit means the last packet of frame received.
+    // 2. Queue has lots of packets, the load is heavy.
+    // 3. The frame contains only one packet for each frame.
+    if (rtp_pkt->rtp_header.get_marker() || queue_->is_heavy() || one_packet_per_frame_) {
         collect_packet();
     }
 
     return err;
 }
 
-srs_error_t SrsRtpQueue::remove(uint16_t seq)
-{
-    srs_error_t err = srs_success;
-
-    SrsRtpSharedPacket*& pkt = queue_[seq % capacity_];
-    if (pkt && pkt->rtp_header.get_sequence() == seq) {
-        delete pkt;
-        pkt = NULL;
-    }
-
-    return err;
-}
-
 void SrsRtpQueue::get_and_clean_collected_frames(std::vector<std::vector<SrsRtpSharedPacket*> >& frames)
 {
     frames.swap(frames_);
@@ -309,44 +366,35 @@ bool SrsRtpQueue::get_and_clean_if_needed_request_key_frame()
 
 void SrsRtpQueue::notify_drop_seq(uint16_t seq)
 {
-    uint16_t s = seq + 1;
-    for ( ; s != highest_sequence_; ++s) {
-        SrsRtpSharedPacket* pkt = queue_[s % capacity_];
-        if (pkt && pkt->rtp_payload_header->is_first_packet_of_frame) {
-            break;
-        }
+    uint16_t next = queue_->next_start_of_frame();
+
+    // Note that low_ mean not found, clear queue util one packet.
+    if (next == queue_->low()) {
+        next = queue_->high() - 1;
     }
 
-    srs_verbose("drop seq=%u, highest seq=%u, update head seq %u to %u", seq, highest_sequence_, head_sequence_, s);
-    head_sequence_ = s;
+    // When NACK is timeout, move to the next start of frame.
+    srs_trace("nack drop seq=%u, drop range [%u, %u]", seq, queue_->low(), next + 1);
+    queue_->advance_to(next + 1);
 }
 
 void SrsRtpQueue::notify_nack_list_full()
 {
-    bool found_key_frame = false;
-    while (head_sequence_ <= highest_sequence_) {
-        SrsRtpSharedPacket* pkt = queue_[head_sequence_ % capacity_];
-        if (pkt && pkt->rtp_payload_header->is_key_frame && pkt->rtp_payload_header->is_first_packet_of_frame) {
-            found_key_frame = true;
-            srs_verbose("found firsr packet of key frame, seq=%u", head_sequence_);
-            break;
-        }
+    uint16_t next = queue_->next_keyframe();
 
-        nack_.remove(head_sequence_);
-        remove(head_sequence_);
-        ++head_sequence_;
+    // Note that low_ mean not found, clear queue util one packet.
+    if (next == queue_->low()) {
+        next = queue_->high() - 1;
     }
 
-    if (!found_key_frame) {
-        srs_verbose("no found first packet of key frame, request key frame");
-        request_key_frame_ = true;
-        head_sequence_ = highest_sequence_;
-    }
+    // When NACK is overflow, move to the next keyframe.
+    srs_trace("nack overflow drop range [%u, %u]", queue_->low(), next + 1);
+    queue_->advance_to(next + 1);
 }
 
 uint32_t SrsRtpQueue::get_extended_highest_sequence()
 {
-    return cycle_ * 65536 + highest_sequence_;
+    return queue_->get_extended_highest_sequence();
 }
 
 uint8_t SrsRtpQueue::get_fraction_lost()
@@ -392,8 +440,8 @@ void SrsRtpQueue::insert_into_nack_list(uint16_t seq_start, uint16_t seq_end)
 void SrsRtpQueue::collect_packet()
 {
     vector<SrsRtpSharedPacket*> frame;
-    for (uint16_t s = head_sequence_; s != highest_sequence_; ++s) {
-        SrsRtpSharedPacket* pkt = queue_[s % capacity_];
+    for (uint16_t s = queue_->low(); s != queue_->high(); ++s) {
+        SrsRtpSharedPacket* pkt = queue_->at(s);
 
         if (nack_.find(s) != NULL) {
             srs_verbose("seq=%u, found in nack list when collect frame", s);
@@ -401,20 +449,18 @@ void SrsRtpQueue::collect_packet()
         }
 
         // We must collect frame from first packet to last packet.
-        if (s == head_sequence_ && pkt->rtp_payload_size() != 0 && !pkt->rtp_payload_header->is_first_packet_of_frame) {
+        if (s == queue_->low() && pkt->rtp_payload_size() != 0 && !pkt->rtp_payload_header->is_first_packet_of_frame) {
             break;
         }
 
         frame.push_back(pkt->copy());
         if (pkt->rtp_header.get_marker() || one_packet_per_frame_) {
-            if (!start_collected_) {
-                start_collected_ = true;
-            }
+            nn_collected_frames++;
             frames_.push_back(frame);
             frame.clear();
 
-            srs_verbose("head seq=%u, update to %u because collect one full farme", head_sequence_, s + 1);
-            head_sequence_ = s + 1;
+            srs_verbose("head seq=%u, update to %u because collect one full farme", queue_->low(), s + 1);
+            queue_->advance_to(s + 1);
         }
     }
 
diff --git a/trunk/src/app/srs_app_rtp_queue.hpp b/trunk/src/app/srs_app_rtp_queue.hpp
index 4b2fb8929..70631e801 100644
--- a/trunk/src/app/srs_app_rtp_queue.hpp
+++ b/trunk/src/app/srs_app_rtp_queue.hpp
@@ -61,21 +61,24 @@ struct SrsRtpNackInfo
     int req_nack_count_;
 };
 
-inline bool seq_cmp(const uint16_t& l, const uint16_t& r)
+// The "distance" between two uint16 number, for example:
+//      distance(low=3, high=5) === (int16_t)(uint16_t)((uint16_t)3-(uint16_t)5) === -2
+//      distance(low=3, high=65534) === (int16_t)(uint16_t)((uint16_t)3-(uint16_t)65534) === 5
+//      distance(low=65532, high=65534) === (int16_t)(uint16_t)((uint16_t)65532-(uint16_t)65534) === -2
+// For RTP sequence, it's only uint16 and may flip back, so 3 maybe 3+0xffff.
+inline bool srs_rtp_seq_distance(const uint16_t& low, const uint16_t& high)
 {
-    return ((int16_t)(r - l)) > 0;
+    return ((int16_t)(high - low)) > 0;
 }
 
-struct SeqComp
-{   
-    bool operator()(const uint16_t& l, const uint16_t& r) const
-    {   
-        return seq_cmp(l, r);
-    }   
-};
-
 class SrsRtpNackList
 {
+private:
+    struct SeqComp {
+        bool operator()(const uint16_t& low, const uint16_t& high) const {
+            return srs_rtp_seq_distance(low, high);
+        }
+    };
 private:
     // Nack queue, seq order, oldest to newest.
     std::map<uint16_t, SrsRtpNackInfo, SeqComp> queue_;
@@ -101,27 +104,64 @@ public:
     void update_rtt(int rtt);
 };
 
-class SrsRtpQueue
+// For UDP, the packets sequence may present as bellow:
+//      [seq1(done)|seq2|seq3 ... seq10|seq11(lost)|seq12|seq13]
+//                   \___(head_sequence_)   \               \___(highest_sequence_)
+//                                           \___(no received, in nack list)
+//      * seq1: The packet is done, we already got the entire frame and processed it.
+//      * seq2,seq3,...,seq10,seq12,seq13: We are processing theses packets, for example, some FU-A or NALUs,
+//               but not an entire video frame right now.
+//      * seq10: This packet is lost or not received, we put it in the nack list.
+// We store the received packets in ring buffer.
+class SrsRtpRingBuffer
 {
 private:
-    /*
-     *[seq1|seq2|seq3|seq4|seq5 ... seq10|seq11(loss)|seq12(loss)|seq13]
-     *             \___(head_sequence_)      \                      \___(highest_sequence_)
-     *                                        \___(no received, in nack list)
-     */
     // Capacity of the ring-buffer.
     uint16_t capacity_;
-    // Thei highest sequence we have receive.
-    uint16_t highest_sequence_;
-    // The sequence waitting to read.
-    uint16_t head_sequence_;
-    bool initialized_;
-    bool start_collected_;
     // Ring bufer.
     SrsRtpSharedPacket** queue_;
+    // Increase one when uint16 flip back, for get_extended_highest_sequence.
+    uint64_t nn_seq_flip_backs;
+    // Whether initialized, because we use uint16 so we can't use -1.
+    bool initialized_;
+private:
+    // Current position we are working at.
+    uint16_t low_;
+    uint16_t high_;
+public:
+    SrsRtpRingBuffer(size_t capacity);
+    virtual ~SrsRtpRingBuffer();
+public:
+    uint16_t low() { return low_; }
+    uint16_t high() { return high_; }
+    void advance_to(uint16_t seq) { low_ = seq; }
+    void set(uint16_t at, SrsRtpSharedPacket* pkt);
+    void remove(uint16_t at);
+    bool overflow() { return low_ + capacity_ < high_; }
+    bool is_heavy() { return high_ - low_ >= capacity_ / 2; }
+    // Get the next start packet of frame.
+    // @remark If not found, return the low_, which should never be the "next" one,
+    // because it MAY or NOT current start packet of frame but never be the next.
+    uint16_t next_start_of_frame();
+    // Get the next seq of keyframe.
+    // @remark Return low_ if not found.
+    uint16_t next_keyframe();
+    // The highest sequence number, calculate the flip back base.
+    uint32_t get_extended_highest_sequence();
+    // Update the sequence, got the nack range by [low, high].
+    void update(uint16_t seq, bool startup, uint16_t& nack_low, uint16_t& nack_high);
+    // Get the packet by seq.
+    SrsRtpSharedPacket* at(uint16_t seq) { return queue_[seq % capacity_]; }
+};
+
+class SrsRtpQueue
+{
+private:
+    uint64_t nn_collected_frames;
+    SrsRtpRingBuffer* queue_;
 private:
-    uint64_t cycle_;
     double jitter_;
+    // TODO: FIXME: Covert time to srs_utime_t.
     int64_t last_trans_time_;
     uint64_t pre_number_of_packet_received_;
     uint64_t pre_number_of_packet_lossed_;
@@ -139,7 +179,6 @@ public:
     virtual ~SrsRtpQueue();
 public:
     srs_error_t insert(SrsRtpSharedPacket* rtp_pkt);
-    srs_error_t remove(uint16_t seq);
 public:
     void get_and_clean_collected_frames(std::vector<std::vector<SrsRtpSharedPacket*> >& frames);
     bool get_and_clean_if_needed_request_key_frame();