diff --git a/trunk/research/players/rtc_player.html b/trunk/research/players/rtc_player.html
index 03d23bd13..28416fd4b 100644
--- a/trunk/research/players/rtc_player.html
+++ b/trunk/research/players/rtc_player.html
@@ -46,7 +46,7 @@
     </div>
 
     <label></label>
-    <video id="rtc_media_player" controls autoplay></video>
+    <video id="rtc_media_player" width="320" controls autoplay></video>
 
     <footer>
         <p></p>
diff --git a/trunk/research/players/rtc_publisher.html b/trunk/research/players/rtc_publisher.html
index bb33c9dec..7945c7044 100644
--- a/trunk/research/players/rtc_publisher.html
+++ b/trunk/research/players/rtc_publisher.html
@@ -46,7 +46,7 @@
     </div>
 
     <label></label>
-    <video id="rtc_media_player" autoplay muted></video>
+    <video id="rtc_media_player" width="320" autoplay muted></video>
 
     <footer>
         <p></p>
@@ -71,10 +71,8 @@
             pc.addTransceiver("video", {direction: "sendonly"});
 
             var constraints = {
-                "audio": true, "video": {
-                    "width": { "min": "480", "max": "720" },
-                    "height": { "min": "320", "max": "480" },
-                    "frameRate": { "min": "15", "max": "30" }
+                audio: true, video: {
+                    height: { max: 320 }
                 }
             };
             navigator.mediaDevices.getUserMedia(
diff --git a/trunk/src/app/srs_app_http_api.cpp b/trunk/src/app/srs_app_http_api.cpp
index 6041e3ced..5516186e5 100644
--- a/trunk/src/app/srs_app_http_api.cpp
+++ b/trunk/src/app/srs_app_http_api.cpp
@@ -1027,8 +1027,14 @@ srs_error_t SrsGoApiRtcPlay::exchange_sdp(const std::string& app, const std::str
             // TODO: check opus format specific param
             std::vector<SrsMediaPayloadType> payloads = remote_media_desc.find_media_with_encoding_name("opus");
             for (std::vector<SrsMediaPayloadType>::iterator iter = payloads.begin(); iter != payloads.end(); ++iter) {
-                // Only choose one match opus codec.
                 local_media_desc.payload_types_.push_back(*iter);
+                SrsMediaPayloadType& payload_type = local_media_desc.payload_types_.back();
+
+                // TODO: FIXME: Only support some transport algorithms.
+                vector<string> rtcp_fb;
+                payload_type.rtcp_fb_.swap(rtcp_fb);
+
+                // Only choose one match opus codec.
                 break;
             }
 
@@ -1050,8 +1056,14 @@ srs_error_t SrsGoApiRtcPlay::exchange_sdp(const std::string& app, const std::str
 
                 // Try to pick the "best match" H.264 payload type.
                 if (h264_param.packetization_mode == "1" && h264_param.level_asymmerty_allow == "1") {
-                    // Only choose first match H.264 payload type.
                     local_media_desc.payload_types_.push_back(*iter);
+                    SrsMediaPayloadType& payload_type = local_media_desc.payload_types_.back();
+
+                    // TODO: FIXME: Only support some transport algorithms.
+                    vector<string> rtcp_fb;
+                    payload_type.rtcp_fb_.swap(rtcp_fb);
+
+                    // Only choose first match H.264 payload type.
                     break;
                 }
 
@@ -1346,8 +1358,14 @@ srs_error_t SrsGoApiRtcPublish::exchange_sdp(const std::string& app, const std::
             // TODO: check opus format specific param
             std::vector<SrsMediaPayloadType> payloads = remote_media_desc.find_media_with_encoding_name("opus");
             for (std::vector<SrsMediaPayloadType>::iterator iter = payloads.begin(); iter != payloads.end(); ++iter) {
-                // Only choose one match opus codec.
                 local_media_desc.payload_types_.push_back(*iter);
+                SrsMediaPayloadType& payload_type = local_media_desc.payload_types_.back();
+
+                // TODO: FIXME: Only support some transport algorithms.
+                vector<string> rtcp_fb;
+                payload_type.rtcp_fb_.swap(rtcp_fb);
+
+                // Only choose one match opus codec.
                 break;
             }
 
@@ -1370,8 +1388,14 @@ srs_error_t SrsGoApiRtcPublish::exchange_sdp(const std::string& app, const std::
 
                 // Try to pick the "best match" H.264 payload type.
                 if (h264_param.packetization_mode == "1" && h264_param.level_asymmerty_allow == "1") {
-                    // Only choose first match H.264 payload type.
                     local_media_desc.payload_types_.push_back(*iter);
+                    SrsMediaPayloadType& payload_type = local_media_desc.payload_types_.back();
+
+                    // TODO: FIXME: Only support some transport algorithms.
+                    vector<string> rtcp_fb;
+                    payload_type.rtcp_fb_.swap(rtcp_fb);
+
+                    // Only choose first match H.264 payload type.
                     break;
                 }
 
@@ -1388,7 +1412,8 @@ srs_error_t SrsGoApiRtcPublish::exchange_sdp(const std::string& app, const std::
                 return srs_error_new(ERROR_RTC_SDP_EXCHANGE, "no found valid H.264 payload type");
             }
 
-            local_media_desc.payload_types_.back().rtcp_fb_.push_back("rrtr");
+            // TODO: FIXME: Support RRTR?
+            //local_media_desc.payload_types_.back().rtcp_fb_.push_back("rrtr");
         }
 
         local_media_desc.mid_ = remote_media_desc.mid_;
@@ -1410,8 +1435,6 @@ srs_error_t SrsGoApiRtcPublish::exchange_sdp(const std::string& app, const std::
             local_media_desc.session_info_.setup_ = "passive";
         }
 
-        local_sdp.media_descs_.back().session_info_.ice_options_ = "trickle";
-
         local_media_desc.rtcp_mux_ = true;
 
         // For publisher, we are always sendonly.
diff --git a/trunk/src/app/srs_app_sdp.cpp b/trunk/src/app/srs_app_sdp.cpp
index 0dc001f60..d2e4b3043 100644
--- a/trunk/src/app/srs_app_sdp.cpp
+++ b/trunk/src/app/srs_app_sdp.cpp
@@ -36,12 +36,12 @@ using namespace std;
 const std::string kCRLF = "\\r\\n";
 
 #define FETCH(is,word) \
-if (! (is >> word)) {\
+if (!(is >> word)) {\
     return srs_error_new(ERROR_RTC_SDP_DECODE, "fetch failed");\
 }\
 
 #define FETCH_WITH_DELIM(is,word,delim) \
-if (! getline(is,word,delim)) {\
+if (!getline(is,word,delim)) {\
     return srs_error_new(ERROR_RTC_SDP_DECODE, "fetch with delim failed");\
 }\
 
@@ -111,6 +111,7 @@ SrsSessionInfo::~SrsSessionInfo()
 srs_error_t SrsSessionInfo::parse_attribute(const std::string& attribute, const std::string& value)
 {
     srs_error_t err = srs_success;
+
     if (attribute == "ice-ufrag") {
         ice_ufrag_ = value;
     } else if (attribute == "ice-pwd") {
@@ -134,23 +135,25 @@ srs_error_t SrsSessionInfo::parse_attribute(const std::string& attribute, const
 srs_error_t SrsSessionInfo::encode(std::ostringstream& os)
 {
     srs_error_t err = srs_success;
-    if (! ice_ufrag_.empty()) {
+
+    if (!ice_ufrag_.empty()) {
         os << "a=ice-ufrag:" << ice_ufrag_ << kCRLF;
     }
-    if (! ice_pwd_.empty()) {
+    
+    if (!ice_pwd_.empty()) {
         os << "a=ice-pwd:" << ice_pwd_ << kCRLF;
     }
-    if (! ice_options_.empty()) {
+
+    // For ICE-lite, we never set the trickle.
+    if (!ice_options_.empty()) {
         os << "a=ice-options:" << ice_options_ << kCRLF;
-    } else {
-        // @see: https://webrtcglossary.com/trickle-ice/
-        // Trickle ICE is an optimization of the ICE specification for NAT traversal.
-        os << "a=ice-options:trickle" << kCRLF;
     }
-    if (! fingerprint_algo_.empty() && ! fingerprint_.empty()) {
+    
+    if (!fingerprint_algo_.empty() && ! fingerprint_.empty()) {
         os << "a=fingerprint:" << fingerprint_algo_ << " " << fingerprint_ << kCRLF;
     }
-    if (! setup_.empty()) {
+    
+    if (!setup_.empty()) {
         os << "a=setup:" << setup_ << kCRLF;
     }
 
@@ -179,22 +182,23 @@ SrsSSRCInfo::~SrsSSRCInfo()
 srs_error_t SrsSSRCInfo::encode(std::ostringstream& os)
 {
     srs_error_t err = srs_success;
+
     if (ssrc_ == 0) {
         return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid ssrc");
     }
 
     os << "a=ssrc:" << ssrc_ << " cname:" << cname_ << kCRLF;
-    if (! msid_.empty()) {
+    if (!msid_.empty()) {
         os << "a=ssrc:" << ssrc_ << " msid:" << msid_;
-        if (! msid_tracker_.empty()) {
+        if (!msid_tracker_.empty()) {
             os << " " << msid_tracker_;
         }
         os << kCRLF;
     }
-    if (! mslabel_.empty()) {
+    if (!mslabel_.empty()) {
         os << "a=ssrc:" << ssrc_ << " mslabel:" << mslabel_ << kCRLF;
     }
-    if (! label_.empty()) {
+    if (!label_.empty()) {
         os << "a=ssrc:" << ssrc_ << " label:" << label_ << kCRLF;
     }
 
@@ -215,7 +219,7 @@ srs_error_t SrsMediaPayloadType::encode(std::ostringstream& os)
     srs_error_t err = srs_success;
 
     os << "a=rtpmap:" << payload_type_ << " " << encoding_name_ << "/" << clock_rate_;
-    if (! encoding_param_.empty()) {
+    if (!encoding_param_.empty()) {
         os << "/" << encoding_param_;
     }
     os << kCRLF;
@@ -224,7 +228,7 @@ srs_error_t SrsMediaPayloadType::encode(std::ostringstream& os)
         os << "a=rtcp-fb:" << payload_type_ << " " << *iter << kCRLF;
     }
 
-    if (! format_specific_param_.empty()) {
+    if (!format_specific_param_.empty()) {
         os << "a=fmtp:" << payload_type_ << " " << format_specific_param_
            // TODO: FIXME: Remove the test code bellow.
            // << ";x-google-max-bitrate=6000;x-google-min-bitrate=5100;x-google-start-bitrate=5000"
@@ -315,10 +319,10 @@ srs_error_t SrsMediaDesc::encode(std::ostringstream& os)
     }
 
     os << "a=mid:" << mid_ << kCRLF;
-    if (! msid_.empty()) {
+    if (!msid_.empty()) {
         os << "a=msid:" << msid_;
         
-        if (! msid_tracker_.empty()) {
+        if (!msid_tracker_.empty()) {
             os << " " << msid_tracker_;
         }
 
@@ -658,7 +662,7 @@ srs_error_t SrsSdp::parse(const std::string& sdp_str)
         if (line.size() < 2 || line[1] != '=') {
             return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid sdp line=%s", line.c_str());
         }
-        if (! line.empty() && line[line.size()-1] == '\r') {
+        if (!line.empty() && line[line.size()-1] == '\r') {
             line.erase(line.size()-1, 1);
         }
 
@@ -681,7 +685,7 @@ srs_error_t SrsSdp::encode(std::ostringstream& os)
     // ice-lite is a minimal version of the ICE specification, intended for servers running on a public IP address.
     os << "a=ice-lite" << kCRLF;
 
-    if (! groups_.empty()) {
+    if (!groups_.empty()) {
         os << "a=group:" << group_policy_;
         for (std::vector<std::string>::iterator iter = groups_.begin(); iter != groups_.end(); ++iter) {
             os << " " << *iter;
@@ -954,7 +958,7 @@ srs_error_t SrsSdp::parse_media_description(const std::string& content)
         media_descs_.back().payload_types_.push_back(SrsMediaPayloadType(fmt));
     }
 
-    if (! in_media_session_) {
+    if (!in_media_session_) {
         in_media_session_ = true;
     }