diff --git a/fec_manager.cpp b/fec_manager.cpp
index c53bb4e..fb08282 100644
--- a/fec_manager.cpp
+++ b/fec_manager.cpp
@@ -20,7 +20,7 @@
 
 fec_parameter_t g_fec_par;
 
-int debug_fec=1;
+int debug_fec=0;
 //int dynamic_update_fec=1;
 
 const int encode_fast_send=1;
@@ -288,15 +288,18 @@ int fec_encode_manager_t::input(char *s,int len/*,int &is_first_packet*/)
     	if(fec_par.mode==0)
     	{
 
-    		actual_data_num=fec_par.get_tail().x;
-    		actual_redundant_num=fec_par.get_tail().y;
+
+    		int tail_x=fec_par.get_tail().x;
+    		int tail_y=fec_par.get_tail().y;
+    		actual_data_num=tail_x;
+    		actual_redundant_num=tail_y;
 
     		if(short_packet_optimize)
     		{
-    			u32_t best_len=(blob_encode.get_shard_len(actual_data_num,0)+header_overhead)*(actual_data_num+actual_redundant_num);
-    			int best_data_num=actual_data_num;
-    			assert(actual_data_num<=fec_par.rs_cnt);
-    			for(int i=1;i<actual_data_num;i++)
+    			u32_t best_len=(blob_encode.get_shard_len(tail_x,0)+header_overhead)*(tail_x+tail_y);
+    			int best_data_num=tail_x;
+    			assert(tail_x<=fec_par.rs_cnt);
+    			for(int i=1;i<tail_x;i++)
     			{
     				assert(fec_par.rs_par[i-1].x==i);
     				int tmp_x=fec_par.rs_par[i-1].x;
@@ -315,14 +318,10 @@ int fec_encode_manager_t::input(char *s,int len/*,int &is_first_packet*/)
     			actual_data_num=best_data_num;
     			assert(best_data_num>=1&&best_data_num<=fec_par.rs_cnt);
     			actual_redundant_num=fec_par.rs_par[best_data_num-1].y;
-
-    			if(debug_fec)
-    				mylog(log_debug,"actual_data_num=%d actual_redundant_num=%d len=%d\n",actual_data_num,actual_redundant_num,blob_encode.get_shard_len(actual_data_num,0));
-    			else
-    				mylog(log_trace,"actual_data_num=%d actual_redundant_num=%d\n",actual_data_num,actual_redundant_num);
     		}
 
         	assert(blob_encode.output(actual_data_num,blob_output,fec_len)==0);
+
     	}
     	else
     	{
@@ -337,7 +336,11 @@ int fec_encode_manager_t::input(char *s,int len/*,int &is_first_packet*/)
     		}
 
     	}
-    	mylog(log_trace,"%d %d %d\n",actual_data_num,actual_redundant_num,fec_len);
+		if(debug_fec)
+			mylog(log_debug,"x=%d y=%d len=%d\n",actual_data_num,actual_redundant_num,fec_len);
+		else
+			mylog(log_trace,"x=%d y=%d len=%d\n",actual_data_num,actual_redundant_num,fec_len);
+    	//mylog(log_trace,"%d %d %d\n",actual_data_num,actual_redundant_num,fec_len);
 
     	char *tmp_output_buf[max_fec_packet_num+5]={0};
     	for(int i=0;i<actual_data_num+actual_redundant_num;i++)
diff --git a/fec_manager.h b/fec_manager.h
index 81e8bd8..41aaa5a 100644
--- a/fec_manager.h
+++ b/fec_manager.h
@@ -19,6 +19,8 @@ const int max_fec_packet_num=255;// this is the limitation of the rs lib
 extern u32_t fec_buff_num;
 
 const int rs_str_len=max_fec_packet_num*10+100;
+extern int header_overhead;
+extern int debug_fec;
 
 struct fec_parameter_t
 {
@@ -50,7 +52,7 @@ struct fec_parameter_t
 				mylog(log_warn,"failed to parse [%s]\n",tmp_str.c_str());
 				return -1;
 			}
-			if(x<1||y<1||x+y>max_fec_packet_num)
+			if(x<1||y<0||x+y>max_fec_packet_num)
 			{
 				mylog(log_warn,"invaild value x=%d y=%d\n",x,y);
 				return -1;
diff --git a/misc.cpp b/misc.cpp
index 563efc8..5ce3caa 100644
--- a/misc.cpp
+++ b/misc.cpp
@@ -650,6 +650,8 @@ void process_arg(int argc, char *argv[])
 		{"queue-len", required_argument,   0,'q'},
 		{"fec", required_argument,   0,'f'},
 		{"jitter", required_argument,   0,'j'},
+		{"header-overhead", required_argument,    0, 1},
+		{"debug-fec", no_argument,    0, 1},
 		{"fifo", required_argument,    0, 1},
 		{"sub-net", required_argument,    0, 1},
 		{"tun-dev", required_argument,    0, 1},
@@ -660,6 +662,7 @@ void process_arg(int argc, char *argv[])
 		{NULL, 0, 0, 0}
       };
     int option_index = 0;
+    assert(g_fec_par.rs_from_str((char *)"20:10")==0);
 
 	for (i = 0; i < argc; i++)
 	{
@@ -939,6 +942,11 @@ void process_arg(int argc, char *argv[])
 				}
 				g_fec_par.timeout*=1000;
 			}
+			else if(strcmp(long_options[option_index].name,"debug-fec")==0)
+			{
+				debug_fec=1;
+				mylog(log_info,"debug_fec enabled\n");
+			}
 			else if(strcmp(long_options[option_index].name,"fifo")==0)
 			{
 				sscanf(optarg,"%s",fifo_file);
@@ -969,6 +977,11 @@ void process_arg(int argc, char *argv[])
 				sscanf(optarg,"%d",&tun_mtu);
 				mylog(log_warn,"changed tun_mtu,tun_mtu=%d\n",tun_mtu);
 			}
+			else if(strcmp(long_options[option_index].name,"header-overhead")==0)
+			{
+				sscanf(optarg,"%d",&header_overhead);
+				mylog(log_warn,"changed header_overhead,header_overhead=%d\n",header_overhead);
+			}
 			else if(strcmp(long_options[option_index].name,"disable-mssfix")==0)
 			{
 				mssfix=0;