diff --git a/webrtc/RtpExt.cpp b/webrtc/RtpExt.cpp
index dd9a1e2e..99581ca7 100644
--- a/webrtc/RtpExt.cpp
+++ b/webrtc/RtpExt.cpp
@@ -561,4 +561,73 @@ void RtpExt::setType(RtpExtType type) {
 
 RtpExtType RtpExt::getType() const {
     return _type;
-}
\ No newline at end of file
+}
+
+RtpExtContext::RtpExtContext(const RtcMedia &m){
+    for (auto &ext : m.extmap) {
+        auto ext_type = RtpExt::getExtType(ext.ext);
+        _rtp_ext_id_to_type.emplace(ext.id, ext_type);
+        _rtp_ext_type_to_id.emplace(ext_type, ext.id);
+    }
+}
+
+string RtpExtContext::getRid(uint32_t ssrc) const{
+    auto it = _ssrc_to_rid.find(ssrc);
+    if (it == _ssrc_to_rid.end()) {
+        return "";
+    }
+    return it->second;
+}
+
+void RtpExtContext::changeRtpExtId(const RtpHeader *header, bool is_recv, string *rid_ptr) {
+    string rid, repaired_rid;
+    auto ext_map = RtpExt::getExtValue(header);
+    for (auto &pr : ext_map) {
+        if (is_recv) {
+            auto it = _rtp_ext_id_to_type.find(pr.first);
+            if (it == _rtp_ext_id_to_type.end()) {
+                WarnL << "接收rtp时,忽略不识别的rtp ext, id=" << (int) pr.first;
+                pr.second.clearExt();
+                continue;
+            }
+            pr.second.setType(it->second);
+            //重新赋值ext id为 ext type，作为后面处理ext的统一中间类型
+            pr.second.setExtId((uint8_t) it->second);
+            switch (it->second) {
+                case RtpExtType::sdes_rtp_stream_id : rid = pr.second.getRtpStreamId(); break;
+                case RtpExtType::sdes_repaired_rtp_stream_id : repaired_rid = pr.second.getRepairedRtpStreamId(); break;
+                default : break;
+            }
+        } else {
+            pr.second.setType((RtpExtType) pr.first);
+            auto it = _rtp_ext_type_to_id.find((RtpExtType) pr.first);
+            if (it == _rtp_ext_type_to_id.end()) {
+                WarnL << "发送rtp时, 忽略不被客户端支持rtp ext:" << pr.second.dumpString();
+                pr.second.clearExt();
+                continue;
+            }
+            //重新赋值ext id为客户端sdp声明的类型
+            pr.second.setExtId(it->second);
+        }
+    }
+
+    if (!is_recv) {
+        return;
+    }
+    if (rid.empty()) {
+        rid = repaired_rid;
+    }
+    auto ssrc = ntohl(header->ssrc);
+    if (rid.empty()) {
+        //获取rid
+        rid = _ssrc_to_rid[ssrc];
+    } else {
+        //设置rid
+        if (_ssrc_to_rid.emplace(ssrc, rid).second) {
+            InfoL << "rid of ssrc " << ssrc << " is:" << rid;
+        }
+    }
+    if (rid_ptr) {
+        *rid_ptr = rid;
+    }
+}
diff --git a/webrtc/RtpExt.h b/webrtc/RtpExt.h
index 9520bac6..71774657 100644
--- a/webrtc/RtpExt.h
+++ b/webrtc/RtpExt.h
@@ -108,5 +108,23 @@ private:
     RtpExtType _type = RtpExtType::padding;
 };
 
+class RtcMedia;
+class RtpExtContext {
+public:
+    using Ptr = std::shared_ptr<RtpExtContext>;
+    RtpExtContext(const RtcMedia &media);
+    ~RtpExtContext() = default;
+
+    string getRid(uint32_t ssrc) const;
+    void changeRtpExtId(const RtpHeader *header, bool is_recv, string *rid_ptr = nullptr);
+
+private:
+    //发送rtp时需要修改rtp ext id
+    map<RtpExtType, uint8_t> _rtp_ext_type_to_id;
+    //接收rtp时需要修改rtp ext id
+    unordered_map<uint8_t, RtpExtType> _rtp_ext_id_to_type;
+    //ssrc --> rid
+    unordered_map<uint32_t/*simulcast ssrc*/, string/*rid*/> _ssrc_to_rid;
+};
 
 #endif //ZLMEDIAKIT_RTPEXT_H
diff --git a/webrtc/WebRtcTransport.cpp b/webrtc/WebRtcTransport.cpp
index 2a1b14f3..5b2ce735 100644
--- a/webrtc/WebRtcTransport.cpp
+++ b/webrtc/WebRtcTransport.cpp
@@ -424,11 +424,7 @@ void WebRtcTransportImp::onStartWebRTC() {
         }
         if (m_offer->type != TrackApplication) {
             //记录rtp ext类型与id的关系，方便接收或发送rtp时修改rtp ext id
-            for (auto &ext : m_offer->extmap) {
-                auto ext_type = RtpExt::getExtType(ext.ext);
-                _rtp_ext_id_to_type.emplace(ext.id, ext_type);
-                _rtp_ext_type_to_id.emplace(ext_type, ext.id);
-            }
+            info->rtp_ext_ctx = std::make_shared<RtpExtContext>(*m_offer);
         }
     }
 
@@ -596,12 +592,8 @@ private:
     function<void(RtpPacket::Ptr rtp)> _on_sort;
 };
 
-std::shared_ptr<RtpChannel> WebRtcTransportImp::MediaTrack::getRtpChannel(uint32_t ssrc) const{
-    auto it_rid = ssrc_to_rid.find(ssrc);
-    if (it_rid == ssrc_to_rid.end()) {
-        return nullptr;
-    }
-    auto it_chn = rtp_channel.find(it_rid->second);
+std::shared_ptr<RtpChannel> MediaTrack::getRtpChannel(uint32_t ssrc) const{
+    auto it_chn = rtp_channel.find(rtp_ext_ctx->getRid(ssrc));
     if (it_chn == rtp_channel.end()) {
         return nullptr;
     }
@@ -694,59 +686,6 @@ void WebRtcTransportImp::onRtcp(const char *buf, size_t len) {
 
 ///////////////////////////////////////////////////////////////////
 
-void WebRtcTransportImp::changeRtpExtId(MediaTrack &info, const RtpHeader *header, bool is_recv, string *rid_ptr) const{
-    string rid, repaired_rid;
-    auto ext_map = RtpExt::getExtValue(header);
-    for (auto &pr : ext_map) {
-        if (is_recv) {
-            auto it = _rtp_ext_id_to_type.find(pr.first);
-            if (it == _rtp_ext_id_to_type.end()) {
-                WarnL << "接收rtp时,忽略不识别的rtp ext, id=" << (int) pr.first;
-                pr.second.clearExt();
-                continue;
-            }
-            pr.second.setType(it->second);
-            //重新赋值ext id为 ext type，作为后面处理ext的统一中间类型
-            pr.second.setExtId((uint8_t) it->second);
-            switch (it->second) {
-                case RtpExtType::sdes_rtp_stream_id : rid = pr.second.getRtpStreamId(); break;
-                case RtpExtType::sdes_repaired_rtp_stream_id : repaired_rid = pr.second.getRepairedRtpStreamId(); break;
-                default : break;
-            }
-        } else {
-            pr.second.setType((RtpExtType) pr.first);
-            auto it = _rtp_ext_type_to_id.find((RtpExtType) pr.first);
-            if (it == _rtp_ext_type_to_id.end()) {
-                WarnL << "发送rtp时, 忽略不被客户端支持rtp ext:" << pr.second.dumpString();
-                pr.second.clearExt();
-                continue;
-            }
-            //重新赋值ext id为客户端sdp声明的类型
-            pr.second.setExtId(it->second);
-        }
-    }
-
-    if (!is_recv) {
-        return;
-    }
-    if (rid.empty()) {
-        rid = repaired_rid;
-    }
-    auto ssrc = ntohl(header->ssrc);
-    if (rid.empty()) {
-        //获取rid
-        rid = info.ssrc_to_rid[ssrc];
-    } else {
-        //设置rid
-        if (info.ssrc_to_rid.emplace(ssrc, rid).second) {
-            InfoL << "rid of ssrc " << ssrc << " is:" << rid;
-        }
-    }
-    if (rid_ptr) {
-        *rid_ptr = rid;
-    }
-}
-
 void WebRtcTransportImp::createRtpChannel(const string &rid, uint32_t ssrc, const MediaTrack::Ptr &info) {
     //rid --> RtpReceiverImp
     auto &ref = info->rtp_channel[rid];
@@ -779,13 +718,8 @@ void WebRtcTransportImp::onRtp(const char *buf, size_t len) {
 
     //修改ext id至统一
     string rid;
-    changeRtpExtId(*info, rtp, true, &rid);
+    info->rtp_ext_ctx->changeRtpExtId(rtp, true, &rid);
 
-#if 0
-    if (rid.empty() && info->media->type == TrackVideo) {
-        WarnL << "ssrc:" << ssrc << ", rtx:" << is_rtx << ",seq:" << ntohs((uint16_t) rtp->seq);
-    }
-#endif
     auto &ref = info->rtp_channel[rid];
     if (!ref) {
         if (is_rtx) {
@@ -910,12 +844,12 @@ void WebRtcTransportImp::onBeforeEncryptRtp(const char *buf, size_t &len, void *
 
     if (!pr->first || !pr->second->plan_rtx) {
         //普通的rtp,或者不支持rtx, 修改目标pt和ssrc
-        changeRtpExtId(*pr->second, header, false);
+        pr->second->rtp_ext_ctx->changeRtpExtId(header, false);
         header->pt = pr->second->plan_rtp->pt;
         header->ssrc = htonl(pr->second->answer_ssrc_rtp);
     } else {
         //重传的rtp, rtx
-        changeRtpExtId(*pr->second, header, false);
+        pr->second->rtp_ext_ctx->changeRtpExtId(header, false);
         header->pt = pr->second->plan_rtx->pt;
         if (pr->second->answer_ssrc_rtx) {
             //有rtx单独的ssrc,有些情况下，浏览器支持rtx，但是未指定rtx单独的ssrc
diff --git a/webrtc/WebRtcTransport.h b/webrtc/WebRtcTransport.h
index 87450ff3..8fc54c15 100644
--- a/webrtc/WebRtcTransport.h
+++ b/webrtc/WebRtcTransport.h
@@ -272,6 +272,27 @@ private:
     uint16_t _last_max_seq = 0;
 };
 
+class MediaTrack {
+public:
+    using Ptr = std::shared_ptr<MediaTrack>;
+    const RtcCodecPlan *plan_rtp;
+    const RtcCodecPlan *plan_rtx;
+    uint32_t offer_ssrc_rtp = 0;
+    uint32_t offer_ssrc_rtx = 0;
+    uint32_t answer_ssrc_rtp = 0;
+    uint32_t answer_ssrc_rtx = 0;
+    const RtcMedia *media;
+    RtpExtContext::Ptr rtp_ext_ctx;
+
+    //for send rtp
+    NackList nack_list;
+    RtcpContext::Ptr rtcp_context_send;
+
+    //for recv rtp
+    unordered_map<string/*rid*/, std::shared_ptr<RtpChannel> > rtp_channel;
+    std::shared_ptr<RtpChannel> getRtpChannel(uint32_t ssrc) const;
+};
+
 class WebRtcTransportImp : public WebRtcTransport, public MediaSourceEvent, public SockInfo, public std::enable_shared_from_this<WebRtcTransportImp>{
 public:
     using Ptr = std::shared_ptr<WebRtcTransportImp>;
@@ -337,27 +358,8 @@ private:
     bool canSendRtp() const;
     bool canRecvRtp() const;
 
-    class MediaTrack {
-    public:
-        using Ptr = std::shared_ptr<MediaTrack>;
-        const RtcCodecPlan *plan_rtp;
-        const RtcCodecPlan *plan_rtx;
-        uint32_t offer_ssrc_rtp = 0;
-        uint32_t offer_ssrc_rtx = 0;
-        uint32_t answer_ssrc_rtp = 0;
-        uint32_t answer_ssrc_rtx = 0;
-        const RtcMedia *media;
-        NackList nack_list;
-        RtcpContext::Ptr rtcp_context_send;
-        unordered_map<string/*rid*/, std::shared_ptr<RtpChannel> > rtp_channel;
-        unordered_map<uint32_t/*simulcast ssrc*/, string/*rid*/> ssrc_to_rid;
-
-        std::shared_ptr<RtpChannel> getRtpChannel(uint32_t ssrc) const;
-    };
-
     void onSortedRtp(MediaTrack &track, const string &rid, RtpPacket::Ptr rtp);
     void onSendNack(MediaTrack &track, const FCI_NACK &nack, uint32_t ssrc);
-    void changeRtpExtId(MediaTrack &track, const RtpHeader *header, bool is_recv, string *rid_ptr = nullptr) const;
     void createRtpChannel(const string &rid, uint32_t ssrc, const MediaTrack::Ptr &info);
 
 private:
@@ -389,8 +391,4 @@ private:
     unordered_map<uint8_t/*pt*/, std::pair<bool/*is rtx*/,MediaTrack::Ptr> > _pt_to_track;
     //根据rtcp的ssrc获取相关信息，只记录rtp的ssrc，rtx的ssrc不记录
     unordered_map<uint32_t/*ssrc*/, MediaTrack::Ptr> _ssrc_to_track;
-    //发送rtp时需要修改rtp ext id
-    map<RtpExtType, uint8_t> _rtp_ext_type_to_id;
-    //接收rtp时需要修改rtp ext id
-    unordered_map<uint8_t, RtpExtType> _rtp_ext_id_to_type;
 };
\ No newline at end of file