nack/rtx支持多次重传，提高抗丢包率

src/Rtcp/RtcpContext.h

@@ -74,7 +74,6 @@ public:
      */
     uint32_t getRtt(uint32_t ssrc) const;
 
-private:
     /**
      * 上次结果与本次结果间应收包数
      */

src/Rtcp/RtcpFCI.cpp

@@ -194,9 +194,13 @@ vector<bool> FCI_NACK::getBitArray() const {
 
 string FCI_NACK::dumpString() const {
     _StrPrinter printer;
-    printer << "pid:" << getPid() << ",blp:" << getBlp() << ",bit array:";
+    auto pid = getPid();
+    printer << "pid:" << pid << ",blp:" << getBlp() << ",dropped rtp seq:";
     for (auto flag : getBitArray()) {
-        printer << flag << " ";
+        if (flag) {
+            printer << pid << " ";
+        }
+        ++pid;
     }
     return std::move(printer);
 }

webrtc/Nack.cpp

@@ -67,10 +67,17 @@ uint32_t NackList::get_cache_ms() {
 
 ////////////////////////////////////////////////////////////////////////////////////////////////
 
-void NackContext::received(uint16_t seq) {
+void NackContext::received(uint16_t seq, bool is_rtx) {
     if (!_last_max_seq && _seq.empty()) {
         _last_max_seq = seq - 1;
     }
+    if (is_rtx || (seq < _last_max_seq && !(seq < 1024 && _last_max_seq > UINT16_MAX - 1024))) {
+        //重传包或
+        //seq回退，且非回环，那么这个应该是重传包
+        onRtx(seq);
+        return;
+    }
+
     _seq.emplace(seq);
     auto max_seq = *_seq.rbegin();
     auto min_seq = *_seq.begin();
@@ -83,6 +90,7 @@ void NackContext::received(uint16_t seq) {
         //回环
         _seq.clear();
         _last_max_seq = min_seq;
+        _nack_send_ntp.clear();
         return;
     }
 
@@ -98,18 +106,19 @@ void NackContext::received(uint16_t seq) {
         }
 
         //有丢包，丢包从_last_max_seq开始
-        if (max_seq - _last_max_seq > FCI_NACK::kBitSize) {
+        auto nack_rtp_count = FCI_NACK::kBitSize;
+        if (max_seq - _last_max_seq > nack_rtp_count) {
             vector<bool> vec;
-            vec.resize(FCI_NACK::kBitSize);
+            vec.resize(FCI_NACK::kBitSize, false);
-            for (auto i = 0; i < FCI_NACK::kBitSize; ++i) {
+            for (auto i = 0; i < nack_rtp_count; ++i) {
                 vec[i] = _seq.find(_last_max_seq + i + 2) == _seq.end();
             }
-            doNack(FCI_NACK(_last_max_seq + 1, vec));
+            doNack(FCI_NACK(_last_max_seq + 1, vec), true);
-            _last_max_seq += FCI_NACK::kBitSize + 1;
+            _last_max_seq += nack_rtp_count + 1;
             if (_last_max_seq >= max_seq) {
                 _seq.clear();
             } else {
-                auto it = _seq.emplace_hint(_seq.begin(), _last_max_seq);
+                auto it = _seq.emplace_hint(_seq.begin(), _last_max_seq + 1);
                 _seq.erase(_seq.begin(), it);
             }
         }
@@ -120,7 +129,10 @@ void NackContext::setOnNack(onNack cb) {
     _cb = std::move(cb);
 }
 
-void NackContext::doNack(const FCI_NACK &nack) {
+void NackContext::doNack(const FCI_NACK &nack, bool record_nack) {
+    if (record_nack) {
+        recordNack(nack);
+    }
     if (_cb) {
         _cb(nack);
     }
@@ -137,3 +149,95 @@ void NackContext::eraseFrontSeq() {
         it = _seq.erase(it);
     }
 }
+
+void NackContext::onRtx(uint16_t seq) {
+    auto it = _nack_send_ntp.find(seq);
+    if (it == _nack_send_ntp.end()) {
+        return;
+    }
+    auto rtt = getCurrentMillisecond() - it->second.update_stamp;
+    _nack_send_ntp.erase(it);
+
+    if (rtt >= 0) {
+        //rtt不肯小于0
+        _rtt = rtt;
+        //InfoL << "rtt:" << rtt;
+    }
+}
+
+void NackContext::recordNack(const FCI_NACK &nack) {
+    auto now = getCurrentMillisecond();
+    auto i = nack.getPid();
+    for (auto flag : nack.getBitArray()) {
+        if (flag) {
+            auto &ref = _nack_send_ntp[i];
+            ref.first_stamp = now;
+            ref.update_stamp = now;
+            ref.nack_count = 1;
+        }
+        ++i;
+    }
+    //记录太多了，移除一部分早期的记录
+    while (_nack_send_ntp.size() > kNackMaxSize) {
+        _nack_send_ntp.erase(_nack_send_ntp.begin());
+    }
+}
+
+uint64_t NackContext::reSendNack() {
+    set<uint16_t> nack_rtp;
+    auto now = getCurrentMillisecond();
+    for (auto it = _nack_send_ntp.begin(); it != _nack_send_ntp.end();) {
+        if (now - it->second.first_stamp > kNackMaxMS) {
+            //该rtp丢失太久了，不再要求重传
+            it = _nack_send_ntp.erase(it);
+            continue;
+        }
+        if (now - it->second.update_stamp < 2 * _rtt) {
+            //距离上次nack不足2倍的rtt，不用再发送nack
+            ++it;
+            continue;
+        }
+        //此rtp需要请求重传
+        nack_rtp.emplace(it->first);
+        //更新nack发送时间戳
+        it->second.update_stamp = now;
+        if (++(it->second.nack_count) == kNackMaxCount) {
+            //nack次数太多，移除之
+            it = _nack_send_ntp.erase(it);
+            continue;
+        }
+        ++it;
+    }
+
+    if (_nack_send_ntp.empty()) {
+        //不需要再发送nack
+        return 0;
+    }
+
+    int pid = -1;
+    vector<bool> vec;
+    for (auto it = nack_rtp.begin(); it != nack_rtp.end();) {
+        if (pid == -1) {
+            pid = *it;
+            vec.resize(16, false);
+            ++it;
+            continue;
+        }
+        auto inc = *it - pid;
+        if (inc > FCI_NACK::kBitSize) {
+            //新的nack包
+            doNack(FCI_NACK(pid, vec), false);
+            pid = -1;
+            continue;
+        }
+        //这个包丢了
+        vec[inc - 1] = true;
+        ++it;
+    }
+    if (pid != -1) {
+        doNack(FCI_NACK(pid, vec), false);
+    }
+
+    //重传间隔不得低于5ms
+    return std::max(_rtt, 5);
+}

webrtc/Nack.h

@@ -36,22 +36,40 @@ private:
 
 class NackContext {
 public:
+    using Ptr = std::shared_ptr<NackContext>;
     using onNack = function<void(const FCI_NACK &nack)>;
+    //最大保留的rtp丢包状态个数
+    static constexpr auto kNackMaxSize = 100;
+    //rtp丢包状态最长保留时间
+    static constexpr auto kNackMaxMS = 3 * 1000;
+    //nack最多请求重传10次
+    static constexpr auto kNackMaxCount = 10;
 
     NackContext() = default;
     ~NackContext() = default;
 
-    void received(uint16_t seq);
+    void received(uint16_t seq, bool is_rtx = false);
     void setOnNack(onNack cb);
+    uint64_t reSendNack();
 
 private:
     void eraseFrontSeq();
-    void doNack(const FCI_NACK &nack);
+    void doNack(const FCI_NACK &nack, bool record_nack);
+    void recordNack(const FCI_NACK &nack);
+    void onRtx(uint16_t seq);
 
 private:
+    int _rtt = 50;
     onNack _cb;
     set<uint16_t> _seq;
     uint16_t _last_max_seq = 0;
+
+    struct NackStatus{
+        uint64_t first_stamp;
+        uint64_t update_stamp;
+        int nack_count = 0;
+    };
+    map<uint16_t/*seq*/, NackStatus > _nack_send_ntp;
 };
 
 #endif //ZLMEDIAKIT_NACK_H

webrtc/SrtpSession.cpp

@@ -239,8 +239,7 @@ namespace RTC
 
 		if (DepLibSRTP::IsError(err))
 		{
-			MS_WARN_TAG(srtp, "srtp_protect() failed: %s", DepLibSRTP::GetErrorString(err));
+            WarnL << "srtp_protect() failed:" << DepLibSRTP::GetErrorString(err);
-
             return false;
 		}
 
@@ -256,8 +255,7 @@ namespace RTC
 
 		if (DepLibSRTP::IsError(err))
 		{
-			MS_DEBUG_TAG(srtp, "srtp_unprotect() failed: %s", DepLibSRTP::GetErrorString(err));
+            WarnL << "srtp_unprotect() failed:" << DepLibSRTP::GetErrorString(err);
-
 			return false;
 		}
 
@@ -272,8 +270,7 @@ namespace RTC
 
 		if (DepLibSRTP::IsError(err))
 		{
-			MS_WARN_TAG(srtp, "srtp_protect_rtcp() failed: %s", DepLibSRTP::GetErrorString(err));
+            WarnL << "srtp_protect_rtcp() failed:" << DepLibSRTP::GetErrorString(err);
-
 			return false;
 		}
 
@@ -289,8 +286,7 @@ namespace RTC
 
 		if (DepLibSRTP::IsError(err))
 		{
-			MS_DEBUG_TAG(srtp, "srtp_unprotect_rtcp() failed: %s", DepLibSRTP::GetErrorString(err));
+            WarnL << "srtp_unprotect_rtcp() failed:" << DepLibSRTP::GetErrorString(err);
-
 			return false;
 		}
 

webrtc/WebRtcTransport.cpp

@@ -97,7 +97,12 @@ void WebRtcTransport::OnDtlsTransportConnected(
         std::string &remoteCert) {
     InfoL;
     _srtp_session_send = std::make_shared<RTC::SrtpSession>(RTC::SrtpSession::Type::OUTBOUND, srtpCryptoSuite, srtpLocalKey, srtpLocalKeyLen);
-    _srtp_session_recv = std::make_shared<RTC::SrtpSession>(RTC::SrtpSession::Type::INBOUND, srtpCryptoSuite, srtpRemoteKey, srtpRemoteKeyLen);
+
+    string srtpRemoteKey_str((char *) srtpRemoteKey, srtpRemoteKeyLen);
+    _srtp_session_recv_alloc = [srtpCryptoSuite, srtpRemoteKey_str]() {
+        return std::make_shared<RTC::SrtpSession>(RTC::SrtpSession::Type::INBOUND, srtpCryptoSuite,
+                                                  (uint8_t *) srtpRemoteKey_str.data(), srtpRemoteKey_str.size());
+    };
     onStartWebRTC();
 }
 
@@ -250,20 +255,20 @@ void WebRtcTransport::inputSockData(char *buf, size_t len, RTC::TransportTuple *
         _dtls_transport->ProcessDtlsData((uint8_t *) buf, len);
         return;
     }
-    if (is_rtp(buf)) {
-        if (_srtp_session_recv->DecryptSrtp((uint8_t *) buf, &len)) {
-            onRtp(buf, len);
-        } else {
     RtpHeader *rtp = (RtpHeader *) buf;
-            WarnL << "srtp_unprotect rtp failed, pt:" << (int)rtp->pt;
+    auto it = _srtp_session_recv.find(rtp->pt);
+    if (it == _srtp_session_recv.end()) {
+        it = _srtp_session_recv.emplace((uint8_t) rtp->pt, _srtp_session_recv_alloc()).first;
+    }
+    if (is_rtp(buf)) {
+        if (it->second->DecryptSrtp((uint8_t *) buf, &len)) {
+            onRtp(buf, len);
         }
         return;
     }
     if (is_rtcp(buf)) {
-        if (_srtp_session_recv->DecryptSrtcp((uint8_t *) buf, &len)) {
+        if (it->second->DecryptSrtcp((uint8_t *) buf, &len)) {
             onRtcp(buf, len);
-        } else {
-            WarnL;
         }
         return;
     }
@@ -585,21 +590,29 @@ SdpAttrCandidate::Ptr WebRtcTransportImp::getIceCandidate() const{
 
 ///////////////////////////////////////////////////////////////////
 
-class RtpChannel : public RtpTrackImp {
+class RtpChannel : public RtpTrackImp, public std::enable_shared_from_this<RtpChannel> {
 public:
-    RtpChannel(RtpTrackImp::OnSorted cb, function<void(const FCI_NACK &nack)> on_nack) {
+    RtpChannel(EventPoller::Ptr poller, RtpTrackImp::OnSorted cb, function<void(const FCI_NACK &nack)> on_nack) {
+        _poller = std::move(poller);
+        _on_nack = std::move(on_nack);
         setOnSorted(std::move(cb));
-        _nack_ctx.setOnNack(std::move(on_nack));
+
+        _nack_ctx.setOnNack([this](const FCI_NACK &nack) {
+            onNack(nack);
+        });
     }
 
     ~RtpChannel() override = default;
 
     RtpPacket::Ptr inputRtp(TrackType type, int sample_rate, uint8_t *ptr, size_t len, bool is_rtx) {
         auto rtp = RtpTrack::inputRtp(type, sample_rate, ptr, len);
-        if (!is_rtx && rtp) {
+        if (!rtp) {
-            //统计rtp接受情况，便于生成nack rtcp包
+            return rtp;
+        }
         auto seq = rtp->getSeq();
-            _nack_ctx.received(seq);
+        _nack_ctx.received(seq, is_rtx);
+        if (!is_rtx) {
+            //统计rtp接受情况，便于生成nack rtcp包
             _rtcp_context.onRtp(seq, rtp->getStamp(), rtp->ntp_stamp, sample_rate, len);
         }
         return rtp;
@@ -610,9 +623,40 @@ public:
         return _rtcp_context.createRtcpRR(ssrc, getSSRC());
     }
 
+    int getLossRate() {
+        return _rtcp_context.geLostInterval() * 100 / _rtcp_context.getExpectedPacketsInterval();
+    }
+
+private:
+    void starNackTimer(){
+        if (_delay_task) {
+            return;
+        }
+        weak_ptr<RtpChannel> weak_self = shared_from_this();
+        _delay_task = _poller->doDelayTask(10, [weak_self]() -> uint64_t {
+            auto strong_self = weak_self.lock();
+            if (!strong_self) {
+                return 0;
+            }
+            auto ret = strong_self->_nack_ctx.reSendNack();
+            if (!ret) {
+                strong_self->_delay_task = nullptr;
+            }
+            return ret;
+        });
+    }
+
+    void onNack(const FCI_NACK &nack) {
+        _on_nack(nack);
+        starNackTimer();
+    }
+
 private:
     NackContext _nack_ctx;
     RtcpContext _rtcp_context{true};
+    EventPoller::Ptr _poller;
+    DelayTask::Ptr _delay_task;
+    function<void(const FCI_NACK &nack)> _on_nack;
 };
 
 std::shared_ptr<RtpChannel> MediaTrack::getRtpChannel(uint32_t ssrc) const{
@@ -638,6 +682,7 @@ void WebRtcTransportImp::onRtcp(const char *buf, size_t len) {
                     if(!rtp_chn){
                         WarnL << "未识别的sr rtcp包:" << rtcp->dumpString();
                     } else {
+                        //InfoL << "接收丢包率,ssrc:" << sr->ssrc << ",loss rate(%):" << rtp_chn->getLossRate();
                         //设置rtp时间戳与ntp时间戳的对应关系
                         rtp_chn->setNtpStamp(sr->rtpts, track->plan_rtp->sample_rate, sr->getNtpUnixStampMS());
                         auto rr = rtp_chn->createRtcpRR(sr, track->answer_ssrc_rtp);
@@ -715,7 +760,7 @@ void WebRtcTransportImp::onRtcp(const char *buf, size_t len) {
 void WebRtcTransportImp::createRtpChannel(const string &rid, uint32_t ssrc, const MediaTrack::Ptr &track) {
     //rid --> RtpReceiverImp
     auto &ref = track->rtp_channel[rid];
-    ref = std::make_shared<RtpChannel>([track, this, rid](RtpPacket::Ptr rtp) mutable {
+    ref = std::make_shared<RtpChannel>(getPoller(),[track, this, rid](RtpPacket::Ptr rtp) mutable {
         onSortedRtp(*track, rid, std::move(rtp));
     }, [track, this, ssrc](const FCI_NACK &nack) mutable {
         onSendNack(*track, nack, ssrc);
@@ -791,7 +836,6 @@ void WebRtcTransportImp::onSendNack(MediaTrack &track, const FCI_NACK &nack, uin
     auto rtcp = RtcpFB::create(RTPFBType::RTCP_RTPFB_NACK, &nack, FCI_NACK::kSize);
     rtcp->ssrc = htons(track.answer_ssrc_rtp);
     rtcp->ssrc_media = htonl(ssrc);
-    DebugL << htonl(ssrc) << " " << nack.getPid();
     sendRtcpPacket((char *) rtcp.get(), rtcp->getSize(), true);
 }
 

webrtc/WebRtcTransport.h

@@ -122,9 +122,10 @@ private:
     std::shared_ptr<RTC::IceServer> _ice_server;
     std::shared_ptr<RTC::DtlsTransport> _dtls_transport;
     std::shared_ptr<RTC::SrtpSession> _srtp_session_send;
-    std::shared_ptr<RTC::SrtpSession> _srtp_session_recv;
     RtcSession::Ptr _offer_sdp;
     RtcSession::Ptr _answer_sdp;
+    function<std::shared_ptr<RTC::SrtpSession>() > _srtp_session_recv_alloc;
+    std::unordered_map<uint8_t /*pt*/, std::shared_ptr<RTC::SrtpSession> > _srtp_session_recv;
 };
 
 class RtpChannel;