diff --git a/README.md b/README.md
index 71ded5a630..527c0e86fc 100755
--- a/README.md
+++ b/README.md
@@ -344,7 +344,8 @@ Remark:
 
 ### SRS 2.0 history
 
-* v2.0, 2015-05-30, fix [#420](https://github.com/simple-rtmp-server/srs/issues/420) remove ts for hls ram mode.
+* v2.0, 2015-06-06, fix [#421](https://github.com/simple-rtmp-server/srs/issues/421) drop video for unkown RTMP header.
+* v2.0, 2015-06-05, fix [#420](https://github.com/simple-rtmp-server/srs/issues/420) remove ts for hls ram mode.
 * v2.0, 2015-05-30, fix [#209](https://github.com/simple-rtmp-server/srs/issues/209) cleanup hls when stop and timeout. 2.0.173.
 * v2.0, 2015-05-29, fix [#409](https://github.com/simple-rtmp-server/srs/issues/409) support pure video hls. 2.0.172.
 * v2.0, 2015-05-28, support [srs-dolphin][srs-dolphin], the multiple-process SRS.
diff --git a/trunk/src/app/srs_app_source.cpp b/trunk/src/app/srs_app_source.cpp
index 6c853533ed..042913b515 100755
--- a/trunk/src/app/srs_app_source.cpp
+++ b/trunk/src/app/srs_app_source.cpp
@@ -1633,6 +1633,18 @@ int SrsSource::on_video(SrsCommonMessage* shared_video)
 {
     int ret = ERROR_SUCCESS;
     
+    // drop any unknown header video.
+    // @see https://github.com/simple-rtmp-server/srs/issues/421
+    if (!SrsFlvCodec::video_is_acceptable(shared_video->payload, shared_video->size)) {
+        char b0 = 0x00;
+        if (shared_video->size > 0) {
+            b0 = shared_video->payload[0];
+        }
+        
+        srs_warn("drop unknown header video, size=%d, bytes[0]=%#x", shared_video->size, b0);
+        return ret;
+    }
+    
     // convert shared_video to msg, user should not use shared_video again.
     // the payload is transfer to msg, and set to NULL in shared_video.
     SrsSharedPtrMessage msg;
diff --git a/trunk/src/kernel/srs_kernel_codec.cpp b/trunk/src/kernel/srs_kernel_codec.cpp
index 21981506c0..0436c25fa2 100644
--- a/trunk/src/kernel/srs_kernel_codec.cpp
+++ b/trunk/src/kernel/srs_kernel_codec.cpp
@@ -266,6 +266,28 @@ bool SrsFlvCodec::audio_is_aac(char* data, int size)
     return sound_format == SrsCodecAudioAAC;
 }
 
+bool SrsFlvCodec::video_is_acceptable(char* data, int size)
+{
+    // 1bytes required.
+    if (size < 1) {
+        return false;
+    }
+    
+    char frame_type = data[0];
+    char codec_id = frame_type & 0x0f;
+    frame_type = (frame_type >> 4) & 0x0f;
+    
+    if (frame_type < 1 || frame_type > 5) {
+        return false;
+    }
+    
+    if (codec_id < 2 || codec_id > 7) {
+        return false;
+    }
+    
+    return true;
+}
+
 string srs_codec_avc_nalu2str(SrsAvcNaluType nalu_type)
 {
     switch (nalu_type) {
diff --git a/trunk/src/kernel/srs_kernel_codec.hpp b/trunk/src/kernel/srs_kernel_codec.hpp
index 702106101a..238feac763 100644
--- a/trunk/src/kernel/srs_kernel_codec.hpp
+++ b/trunk/src/kernel/srs_kernel_codec.hpp
@@ -222,6 +222,12 @@ class SrsFlvCodec
     * check codec aac.
     */
     static bool audio_is_aac(char* data, int size);
+    /**
+     * check the video RTMP/flv header info,
+     * @return true if video RTMP/flv header is ok.
+     * @remark all type of audio is possible, no need to check audio.
+     */
+    static bool video_is_acceptable(char* data, int size);
 };
 
 /**