diff --git a/trunk/src/app/srs_app_http_conn.cpp b/trunk/src/app/srs_app_http_conn.cpp
index 36ddf4f3f..779197d50 100644
--- a/trunk/src/app/srs_app_http_conn.cpp
+++ b/trunk/src/app/srs_app_http_conn.cpp
@@ -219,9 +219,10 @@ int SrsAacStreamEncoder::write_video(int64_t timestamp, char* data, int size)
     return enc->write_video(timestamp, data, size);
 }
 
-int SrsAacStreamEncoder::write_metadata(int64_t timestamp, char* data, int size)
+int SrsAacStreamEncoder::write_metadata(int64_t /*timestamp*/, char* /*data*/, int /*size*/)
 {
-    return enc->write_metadata(timestamp, data, size);
+    // aac ignore any flv metadata.
+    return ERROR_SUCCESS;
 }
 
 SrsStreamWriter::SrsStreamWriter(ISrsGoHttpResponseWriter* w)
diff --git a/trunk/src/kernel/srs_kernel_aac.cpp b/trunk/src/kernel/srs_kernel_aac.cpp
index c2bc4903c..f074cadfc 100644
--- a/trunk/src/kernel/srs_kernel_aac.cpp
+++ b/trunk/src/kernel/srs_kernel_aac.cpp
@@ -58,8 +58,8 @@ int SrsAacEncoder::initialize(SrsFileWriter* fs)
     srs_assert(fs);
     
     if (!fs->is_open()) {
-        ret = ERROR_KERNEL_FLV_STREAM_CLOSED;
-        srs_warn("stream is not open for decoder. ret=%d", ret);
+        ret = ERROR_KERNEL_AAC_STREAM_CLOSED;
+        srs_warn("stream is not open for encoder. ret=%d", ret);
         return ret;
     }
     
@@ -68,77 +68,6 @@ int SrsAacEncoder::initialize(SrsFileWriter* fs)
     return ret;
 }
 
-int SrsAacEncoder::write_header()
-{
-    int ret = ERROR_SUCCESS;
-    
-    // 9bytes header and 4bytes first previous-tag-size
-    static char flv_header[] = {
-        'F', 'L', 'V', // Signatures "FLV"
-        (char)0x01, // File version (for example, 0x01 for FLV version 1)
-        (char)0x00, // 4, audio; 1, video; 5 audio+video.
-        (char)0x00, (char)0x00, (char)0x00, (char)0x09 // DataOffset UI32 The length of this header in bytes
-    };
-    
-    // flv specification should set the audio and video flag,
-    // actually in practise, application generally ignore this flag,
-    // so we generally set the audio/video to 0.
-    
-    // write 9bytes header.
-    if ((ret = write_header(flv_header)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    
-    return ret;
-}
-
-int SrsAacEncoder::write_header(char flv_header[9])
-{
-    int ret = ERROR_SUCCESS;
-    
-    // write data.
-    if ((ret = _fs->write(flv_header, 9, NULL)) != ERROR_SUCCESS) {
-        srs_error("write flv header failed. ret=%d", ret);
-        return ret;
-    }
-    
-    char pts[] = { (char)0x00, (char)0x00, (char)0x00, (char)0x00 };
-    if ((ret = _fs->write(pts, 4, NULL)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    
-    return ret;
-}
-
-int SrsAacEncoder::write_metadata(char type, char* data, int size)
-{
-    int ret = ERROR_SUCCESS;
-    
-    srs_assert(data);
-    
-    // 11 bytes tag header
-    static char tag_header[] = {
-        (char)type, // TagType UB [5], 18 = script data
-        (char)0x00, (char)0x00, (char)0x00, // DataSize UI24 Length of the message.
-        (char)0x00, (char)0x00, (char)0x00, // Timestamp UI24 Time in milliseconds at which the data in this tag applies.
-        (char)0x00, // TimestampExtended UI8
-        (char)0x00, (char)0x00, (char)0x00, // StreamID UI24 Always 0.
-    };
-    
-    // write data size.
-    if ((ret = tag_stream->initialize(tag_header + 1, 3)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    tag_stream->write_3bytes(size);
-    
-    if ((ret = write_tag(tag_header, sizeof(tag_header), data, size)) != ERROR_SUCCESS) {
-        srs_error("write flv data tag failed. ret=%d", ret);
-        return ret;
-    }
-    
-    return ret;
-}
-
 int SrsAacEncoder::write_audio(int64_t timestamp, char* data, int size)
 {
     int ret = ERROR_SUCCESS;
@@ -147,29 +76,6 @@ int SrsAacEncoder::write_audio(int64_t timestamp, char* data, int size)
     
     timestamp &= 0x7fffffff;
     
-    // 11bytes tag header
-    static char tag_header[] = {
-        (char)8, // TagType UB [5], 8 = audio
-        (char)0x00, (char)0x00, (char)0x00, // DataSize UI24 Length of the message.
-        (char)0x00, (char)0x00, (char)0x00, // Timestamp UI24 Time in milliseconds at which the data in this tag applies.
-        (char)0x00, // TimestampExtended UI8
-        (char)0x00, (char)0x00, (char)0x00, // StreamID UI24 Always 0.
-    };
-    
-    // write data size.
-    if ((ret = tag_stream->initialize(tag_header + 1, 7)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    tag_stream->write_3bytes(size);
-    tag_stream->write_3bytes((int32_t)timestamp);
-    // default to little-endian
-    tag_stream->write_1bytes((timestamp >> 24) & 0xFF);
-    
-    if ((ret = write_tag(tag_header, sizeof(tag_header), data, size)) != ERROR_SUCCESS) {
-        srs_error("write flv audio tag failed. ret=%d", ret);
-        return ret;
-    }
-    
     return ret;
 }
 
@@ -181,66 +87,6 @@ int SrsAacEncoder::write_video(int64_t timestamp, char* data, int size)
     
     timestamp &= 0x7fffffff;
     
-    // 11bytes tag header
-    static char tag_header[] = {
-        (char)9, // TagType UB [5], 9 = video
-        (char)0x00, (char)0x00, (char)0x00, // DataSize UI24 Length of the message.
-        (char)0x00, (char)0x00, (char)0x00, // Timestamp UI24 Time in milliseconds at which the data in this tag applies.
-        (char)0x00, // TimestampExtended UI8
-        (char)0x00, (char)0x00, (char)0x00, // StreamID UI24 Always 0.
-    };
-    
-    // write data size.
-    if ((ret = tag_stream->initialize(tag_header + 1, 7)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    tag_stream->write_3bytes(size);
-    tag_stream->write_3bytes((int32_t)timestamp);
-    // default to little-endian
-    tag_stream->write_1bytes((timestamp >> 24) & 0xFF);
-    
-    if ((ret = write_tag(tag_header, sizeof(tag_header), data, size)) != ERROR_SUCCESS) {
-        srs_error("write flv video tag failed. ret=%d", ret);
-        return ret;
-    }
-    
     return ret;
 }
 
-int SrsAacEncoder::size_tag(int data_size)
-{
-    srs_assert(data_size >= 0);
-    return SRS_FLV_TAG_HEADER_SIZE + data_size + SRS_FLV_PREVIOUS_TAG_SIZE;
-}
-
-int SrsAacEncoder::write_tag(char* header, int header_size, char* tag, int tag_size)
-{
-    int ret = ERROR_SUCCESS;
-    
-    // write tag header.
-    if ((ret = _fs->write(header, header_size, NULL)) != ERROR_SUCCESS) {
-        srs_error("write flv tag header failed. ret=%d", ret);
-        return ret;
-    }
-    
-    // write tag data.
-    if ((ret = _fs->write(tag, tag_size, NULL)) != ERROR_SUCCESS) {
-        srs_error("write flv tag failed. ret=%d", ret);
-        return ret;
-    }
-    
-    // PreviousTagSizeN UI32 Size of last tag, including its header, in bytes.
-    static char pre_size[SRS_FLV_PREVIOUS_TAG_SIZE];
-    if ((ret = tag_stream->initialize(pre_size, SRS_FLV_PREVIOUS_TAG_SIZE)) != ERROR_SUCCESS) {
-        return ret;
-    }
-    tag_stream->write_4bytes(tag_size + header_size);
-    if ((ret = _fs->write(pre_size, sizeof(pre_size), NULL)) != ERROR_SUCCESS) {
-        srs_error("write flv previous tag size failed. ret=%d", ret);
-        return ret;
-    }
-    
-    return ret;
-}
-
-
diff --git a/trunk/src/kernel/srs_kernel_aac.hpp b/trunk/src/kernel/srs_kernel_aac.hpp
index c0a4347a2..3cca8b672 100644
--- a/trunk/src/kernel/srs_kernel_aac.hpp
+++ b/trunk/src/kernel/srs_kernel_aac.hpp
@@ -55,39 +55,12 @@ public:
     */
     virtual int initialize(SrsFileWriter* fs);
 public:
-    /**
-    * write flv header.
-    * write following:
-    *   1. E.2 The FLV header
-    *   2. PreviousTagSize0 UI32 Always 0
-    * that is, 9+4=13bytes.
-    */
-    virtual int write_header();
-    virtual int write_header(char flv_header[9]);
-    /**
-    * write flv metadata. 
-    * @param type, the type of data, or other message type.
-    * @param data, the amf0 metadata which serialize from:
-    *   AMF0 string: onMetaData,
-    *   AMF0 object: the metadata object.
-    * @remark assert data is not NULL.
-    */
-    virtual int write_metadata(char type, char* data, int size);
     /**
     * write audio/video packet.
     * @remark assert data is not NULL.
     */
     virtual int write_audio(int64_t timestamp, char* data, int size);
     virtual int write_video(int64_t timestamp, char* data, int size);
-public:
-    /**
-    * get the tag size,
-    * including the tag header, body, and 4bytes previous tag size.
-    * @remark assert data_size is not negative.
-    */
-    static int size_tag(int data_size);
-private:
-    virtual int write_tag(char* header, int header_size, char* tag, int tag_size);
 };
 
 #endif
diff --git a/trunk/src/kernel/srs_kernel_error.hpp b/trunk/src/kernel/srs_kernel_error.hpp
index 7a9054097..f64fe3b92 100644
--- a/trunk/src/kernel/srs_kernel_error.hpp
+++ b/trunk/src/kernel/srs_kernel_error.hpp
@@ -203,6 +203,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #define ERROR_AAC_ADTS_HEADER               3047
 #define ERROR_AAC_DATA_INVALID              3048
 #define ERROR_HTTP_STATUS_INVLIAD           3049
+#define ERROR_KERNEL_AAC_STREAM_CLOSED      3050
 
 ///////////////////////////////////////////////////////
 // HTTP protocol error.
diff --git a/trunk/src/kernel/srs_kernel_flv.cpp b/trunk/src/kernel/srs_kernel_flv.cpp
index c7aeb6ac2..13e923ef5 100644
--- a/trunk/src/kernel/srs_kernel_flv.cpp
+++ b/trunk/src/kernel/srs_kernel_flv.cpp
@@ -59,7 +59,7 @@ int SrsFlvEncoder::initialize(SrsFileWriter* fs)
     
     if (!fs->is_open()) {
         ret = ERROR_KERNEL_FLV_STREAM_CLOSED;
-        srs_warn("stream is not open for decoder. ret=%d", ret);
+        srs_warn("stream is not open for encoder. ret=%d", ret);
         return ret;
     }