diff --git a/trunk/src/app/srs_app_rtc_sdp.cpp b/trunk/src/app/srs_app_rtc_sdp.cpp
index 4b428ace1..a0f6f9473 100644
--- a/trunk/src/app/srs_app_rtc_sdp.cpp
+++ b/trunk/src/app/srs_app_rtc_sdp.cpp
@@ -332,6 +332,20 @@ vector<SrsMediaPayloadType> SrsMediaDesc::find_media_with_encoding_name(const st
     return payloads;
 }
 
+srs_error_t SrsMediaDesc::update_msid(string id)
+{
+    srs_error_t err = srs_success;
+
+    for(vector<SrsSSRCInfo>::iterator it = ssrc_infos_.begin(); it != ssrc_infos_.end(); ++it) {
+        SrsSSRCInfo& info = *it;
+
+        info.msid_ = id;
+        info.mslabel_ = id;
+    }
+
+    return err;
+}
+
 srs_error_t SrsMediaDesc::parse_line(const std::string& line)
 {
     srs_error_t err = srs_success;
@@ -1072,3 +1086,21 @@ bool SrsSdp::is_unified() const
     return media_descs_.size() > 2;
 }
 
+srs_error_t SrsSdp::update_msid(string id)
+{
+    srs_error_t err = srs_success;
+
+    msids_.clear();
+    msids_.push_back(id);
+
+    for (vector<SrsMediaDesc>::iterator it = media_descs_.begin(); it != media_descs_.end(); ++it) {
+        SrsMediaDesc& desc = *it;
+
+        if ((err = desc.update_msid(id)) != srs_success) {
+            return srs_error_wrap(err, "desc %s update msid %s", desc.mid_.c_str(), id.c_str());
+        }
+    }
+
+    return err;
+}
+
diff --git a/trunk/src/app/srs_app_rtc_sdp.hpp b/trunk/src/app/srs_app_rtc_sdp.hpp
index d4edd6e55..cbf926d54 100644
--- a/trunk/src/app/srs_app_rtc_sdp.hpp
+++ b/trunk/src/app/srs_app_rtc_sdp.hpp
@@ -140,6 +140,7 @@ public:
     SrsMediaPayloadType* find_media_with_payload_type(int payload_type);
     std::vector<SrsMediaPayloadType> find_media_with_encoding_name(const std::string& encoding_name) const;
     const std::map<int, std::string>& get_extmaps() const { return extmaps_; }
+    srs_error_t update_msid(std::string id);
 
     bool is_audio() const { return type_ == "audio"; }
     bool is_video() const { return type_ == "video"; }
@@ -248,6 +249,8 @@ public:
     std::vector<SrsMediaDesc> media_descs_;
 
      bool is_unified() const;
+    // TODO: FIXME: will be fixed when use single pc.
+    srs_error_t update_msid(std::string id);
 };
 
 #endif