diff --git a/trunk/research/librtmp/srs_detect_rtmp.c b/trunk/research/librtmp/srs_detect_rtmp.c
index 4e5f400eb..6323b5e19 100644
--- a/trunk/research/librtmp/srs_detect_rtmp.c
+++ b/trunk/research/librtmp/srs_detect_rtmp.c
@@ -79,8 +79,8 @@ int main(int argc, char** argv)
     printf("duration: %ds, timeout:%ds\n", duration, timeout);
     
     if (duration <= 0 || timeout <= 0) {
-        printf("duration and timeout must be positive.\n");
         ret = 1;
+        fprintf(stderr, "duration and timeout must be positive. ret=%d\n", ret);
         exit(ret);
         return ret;
     }
@@ -88,33 +88,33 @@ int main(int argc, char** argv)
     rtmp = srs_rtmp_create(rtmp_url);
     
     if ((ret = __srs_dns_resolve(rtmp)) != 0) {
-        printf("dns resolve failed.\n");
+        fprintf(stderr, "dns resolve failed. ret=%d\n", ret);
         goto rtmp_destroy;
     }
     printf("dns resolve success\n");
     time_dns_resolve = srs_get_time_ms();
     
     if ((ret = __srs_connect_server(rtmp)) != 0) {
-        printf("socket connect failed.\n");
+        fprintf(stderr, "socket connect failed. ret=%d\n", ret);
         goto rtmp_destroy;
     }
     printf("socket connect success\n");
     time_socket_connect = srs_get_time_ms();
     
     if ((ret = __srs_do_simple_handshake(rtmp)) != 0) {
-        printf("do simple handshake failed.\n");
+        fprintf(stderr, "do simple handshake failed. ret=%d\n", ret);
         goto rtmp_destroy;
     }
     printf("do simple handshake success\n");
     
     if ((ret = srs_connect_app(rtmp)) != 0) {
-        printf("connect vhost/app failed.\n");
+        fprintf(stderr, "connect vhost/app failed. ret=%d\n", ret);
         goto rtmp_destroy;
     }
     printf("connect vhost/app success\n");
     
     if ((ret = srs_play_stream(rtmp)) != 0) {
-        printf("play stream failed.\n");
+        fprintf(stderr, "play stream failed. ret=%d\n", ret);
         goto rtmp_destroy;
     }
     printf("play stream success\n");
@@ -122,6 +122,7 @@ int main(int argc, char** argv)
     
     for (;;) {
         if ((ret = srs_read_packet(rtmp, &type, &timestamp, &data, &size)) != 0) {
+            fprintf(stderr, "read packet failed. ret=%d\n", ret);
             goto rtmp_destroy;
         }
         printf("got packet: type=%s, time=%d, size=%d\n", srs_type2string(type), timestamp, size);
@@ -158,7 +159,7 @@ rtmp_destroy:
         "\"%s\":%d, " // #6
         "\"%s\":%d, " // #7
         "\"%s\":%d, " // #8
-        "%s%s%s%s}",
+        "%s,%s,%s,%s}",
         "code", ret, //#0
         // total = dns + tcp_connect + start_play + first_packet + last_packet
         "total", (int)(time_cleanup - time_startup), //#1
@@ -173,12 +174,12 @@ rtmp_destroy:
         // delay = actual - expect
         "delay", (int)(timestamp - (time_cleanup - time_first_packet)), //#8
         // unit in ms.
-        "\"unit\": \"ms\",",
-        "\"remark0\": \"total = dns + tcp_connect + start_play + first_packet + last_packet\",",
+        "\"unit\": \"ms\"",
+        "\"remark0\": \"total = dns + tcp_connect + start_play + first_packet + last_packet\"",
         "\"remark1\": \"delay = stream - (time_cleanup - time_first_packet)\"",
         "\"remark2\": \"if code is not 0, user must ignore all data\""
     );
     printf("\n");
     
-    return 0;
+    return ret;
 }
diff --git a/trunk/src/kernel/srs_kernel_buffer.cpp b/trunk/src/kernel/srs_kernel_buffer.cpp
index b5e7440f2..2a5f96372 100644
--- a/trunk/src/kernel/srs_kernel_buffer.cpp
+++ b/trunk/src/kernel/srs_kernel_buffer.cpp
@@ -58,7 +58,9 @@ char* SrsBuffer::bytes()
 
 void SrsBuffer::erase(int size)
 {
-    srs_assert(size > 0);
+    if (size <= 0) {
+        return;
+    }
     
     if (size >= length()) {
         data.clear();
diff --git a/trunk/src/kernel/srs_kernel_buffer.hpp b/trunk/src/kernel/srs_kernel_buffer.hpp
index 5942d0f12..f53c7963a 100644
--- a/trunk/src/kernel/srs_kernel_buffer.hpp
+++ b/trunk/src/kernel/srs_kernel_buffer.hpp
@@ -71,7 +71,7 @@ public:
     * erase size of bytes from begin.
     * @param size to erase size of bytes. 
     *       clear if size greater than or equals to length()
-    * @remark assert size is positive.
+    * @remark ignore size is not positive.
     */
     virtual void erase(int size);
     /**
diff --git a/trunk/src/utest/srs_utest_buffer.cpp b/trunk/src/utest/srs_utest_buffer.cpp
index b540c53c8..cb141c931 100644
--- a/trunk/src/utest/srs_utest_buffer.cpp
+++ b/trunk/src/utest/srs_utest_buffer.cpp
@@ -79,20 +79,34 @@ VOID TEST(BufferTest, EraseBytes)
 {
     SrsBuffer b;
     
+    b.erase(0);
+    b.erase(-1);
+    EXPECT_EQ(0, b.length());
+    
     char winlin[] = "winlin";
     b.append(winlin, strlen(winlin));
     b.erase(b.length());
     EXPECT_EQ(0, b.length());
     
+    b.erase(0);
+    b.erase(-1);
+    EXPECT_EQ(0, b.length());
+    
     b.append(winlin, strlen(winlin));
     b.erase(1);
     EXPECT_EQ(5, b.length());
     EXPECT_EQ('i', b.bytes()[0]);
     EXPECT_EQ('n', b.bytes()[4]);
+    
     b.erase(2);
     EXPECT_EQ(3, b.length());
     EXPECT_EQ('l', b.bytes()[0]);
     EXPECT_EQ('n', b.bytes()[2]);
+    
+    b.erase(0);
+    b.erase(-1);
+    EXPECT_EQ(3, b.length());
+    
     b.erase(3);
     EXPECT_EQ(0, b.length());
 }