diff --git a/trunk/src/app/srs_app_config.cpp b/trunk/src/app/srs_app_config.cpp
index c2ff3f989..9e29c6633 100644
--- a/trunk/src/app/srs_app_config.cpp
+++ b/trunk/src/app/srs_app_config.cpp
@@ -1932,10 +1932,12 @@ string SrsConfig::get_transcode_ffmpeg(SrsConfDirective* transcode)
     return conf->arg0();
 }
 
-void SrsConfig::get_transcode_engines(SrsConfDirective* transcode, vector<SrsConfDirective*>& engines)
+vector<SrsConfDirective*> SrsConfig::get_transcode_engines(SrsConfDirective* transcode)
 {
+    vector<SrsConfDirective*> engines;
+    
     if (!transcode) {
-        return;
+        return engines;
     }
     
     for (int i = 0; i < (int)transcode->directives.size(); i++) {
@@ -1946,7 +1948,7 @@ void SrsConfig::get_transcode_engines(SrsConfDirective* transcode, vector<SrsCon
         }
     }
     
-    return;
+    return engines;
 }
 
 bool SrsConfig::get_engine_enabled(SrsConfDirective* engine)
diff --git a/trunk/src/app/srs_app_config.hpp b/trunk/src/app/srs_app_config.hpp
index f0b5f2536..42821ef7a 100644
--- a/trunk/src/app/srs_app_config.hpp
+++ b/trunk/src/app/srs_app_config.hpp
@@ -526,57 +526,80 @@ public:
 // bwct(bandwidth check tool) section
 public:
     /**
-    * 
+    * whether bw check enabled for vhost.
+    * if enabled, serve all clients with bandwidth check services.
+    * oterwise, serve all cleints with stream.
     */
     virtual bool                get_bw_check_enabled(std::string vhost);
     /**
-    * 
+    * the key of server, if client key mot match, reject.
     */
     virtual std::string         get_bw_check_key(std::string vhost);
     /**
-    * 
+    * the check interval, in ms.
+    * if the client request check in very short time(in the interval),
+    * SRS will reject client.
+    * @remark this is used to prevent the bandwidth check attack.
     */
     virtual int                 get_bw_check_interval_ms(std::string vhost);
     /**
-    * 
+    * the max kbps that user can test,
+    * if exceed the kbps, server will slowdown the send-recv.
+    * @remark this is used to protect the service bandwidth.
     */
     virtual int                 get_bw_check_limit_kbps(std::string vhost);
 // vhost edge section
 public:
     /**
-    * 
+    * whether vhost is edge mode.
+    * for edge, publish client will be proxyed to upnode,
+    * for edge, play client will share a connection to get stream from upnode.
     */
     virtual bool                get_vhost_is_edge(std::string vhost);
     /**
-    * 
+    * whether vhost is edge mode.
+    * for edge, publish client will be proxyed to upnode,
+    * for edge, play client will share a connection to get stream from upnode.
     */
     virtual bool                get_vhost_is_edge(SrsConfDirective* vhost);
     /**
-    * 
+    * get the origin config of edge,
+    * specifies the origin ip address, port.
     */
     virtual SrsConfDirective*   get_vhost_edge_origin(std::string vhost);
     /**
-    * 
+    * whether edge token tranverse is enabled,
+    * if true, edge will send connect origin to verfy the token of client.
+    * for example, we verify all clients on the origin FMS by server-side as,
+    * all clients connected to edge must be tranverse to origin to verify.
     */
     virtual bool                get_vhost_edge_token_traverse(std::string vhost);
 // vhost transcode section
 public:
     /**
-    * 
+    * get the transcode directive of vhost in specified scope.
+    * @param vhost, the vhost name to get the transcode directive.
+    * @param scope, the scope, empty to get all. for example, user can transcode
+    *       the app scope stream, by config with app:
+    *                   transcode live {...}
+    *       when the scope is "live", this directive is matched.
+    *       the scope can be: empty for all, app, app/stream.
+    * @remark, please see the samples of full.conf, the app.transcode.srs.com
+    *       and stream.transcode.srs.com.
     */
     virtual SrsConfDirective*   get_transcode(std::string vhost, std::string scope);
     /**
-    * 
+    * whether the transcode directive is enabled.
     */
     virtual bool                get_transcode_enabled(SrsConfDirective* transcode);
     /**
-    * 
+    * get the ffmpeg tool path of transcode.
     */
     virtual std::string         get_transcode_ffmpeg(SrsConfDirective* transcode);
     /**
-    * 
+    * get the engines of transcode.
     */
-    virtual void                get_transcode_engines(SrsConfDirective* transcode, std::vector<SrsConfDirective*>& engines);
+    virtual std::vector<SrsConfDirective*>      get_transcode_engines(SrsConfDirective* transcode);
     /**
     * 
     */
diff --git a/trunk/src/app/srs_app_encoder.cpp b/trunk/src/app/srs_app_encoder.cpp
index 50fe7daaf..7393f0f59 100644
--- a/trunk/src/app/srs_app_encoder.cpp
+++ b/trunk/src/app/srs_app_encoder.cpp
@@ -224,8 +224,7 @@ int SrsEncoder::parse_ffmpeg(SrsRequest* req, SrsConfDirective* conf)
     }
     
     // get all engines.
-    std::vector<SrsConfDirective*> engines;
-    _srs_config->get_transcode_engines(conf, engines);
+    std::vector<SrsConfDirective*> engines = _srs_config->get_transcode_engines(conf);
     if (engines.empty()) {
         srs_trace("ignore the empty transcode engine: %s", 
             conf->arg0().c_str());
diff --git a/trunk/src/app/srs_app_ingest.cpp b/trunk/src/app/srs_app_ingest.cpp
index 9f472de01..4b2178449 100644
--- a/trunk/src/app/srs_app_ingest.cpp
+++ b/trunk/src/app/srs_app_ingest.cpp
@@ -123,8 +123,7 @@ int SrsIngester::parse_engines(SrsConfDirective* vhost, SrsConfDirective* ingest
     }
     
     // get all engines.
-    std::vector<SrsConfDirective*> engines;
-    _srs_config->get_transcode_engines(ingest, engines);
+    std::vector<SrsConfDirective*> engines = _srs_config->get_transcode_engines(ingest);
     if (engines.empty()) {
         SrsFFMPEG* ffmpeg = new SrsFFMPEG(ffmpeg_bin);
         if ((ret = initialize_ffmpeg(ffmpeg, vhost, ingest, NULL)) != ERROR_SUCCESS) {