diff --git a/PcapSender/main.cpp b/PcapSender/main.cpp
index 559c74e..4372c4d 100644
--- a/PcapSender/main.cpp
+++ b/PcapSender/main.cpp
@@ -159,7 +159,7 @@ ReadPcapAndSend(int socket, sockaddr_in &addr, const string &filename, const str
             current_time.tv_sec = inital_time.tv_sec + real_now.tv_sec;
             current_time.tv_nsec = inital_time.tv_nsec + real_now.tv_nsec;
             gaptime = TimeDiff(nowtime, current_time);
-            if (gaptime.tv_nsec >= 0 && gaptime.tv_sec >= 0) {
+            if (gaptime.tv_nsec > 0 || gaptime.tv_sec > 0) {
                 nanosleep(&gaptime, NULL);
             } else {
                 // cout<<" s:" << gaptime.tv_sec<<" ns:" << gaptime.tv_nsec <<endl;
diff --git a/src/base/frame.h b/src/base/frame.h
index b3a3190..c7aeed1 100644
--- a/src/base/frame.h
+++ b/src/base/frame.h
@@ -7,6 +7,8 @@
 #include <vector>
 
 namespace sign {
+class RTPManager;
+
 class Frame : std::enable_shared_from_this<Frame> {
 public:
     using Ptr = std::shared_ptr<Frame>;
@@ -41,6 +43,7 @@ public:
 
 private:
     Frame(Type type, const void *data, size_t len);
+    friend class RTPManager;
 
 private:
     Event _event{true};
diff --git a/src/base/rtp_manager.cpp b/src/base/rtp_manager.cpp
index 5e758bc..1d3d95d 100644
--- a/src/base/rtp_manager.cpp
+++ b/src/base/rtp_manager.cpp
@@ -225,9 +225,32 @@ RTPManager::ModifySEIPacket(RTPDecoder::DecodedPacket packet, void *sei_begin, v
     // TODO: @tqcq 增加对padding udp rtp sei包的处理
     auto last_packet = packet.ref_rtp_packets.back();
     auto last_frame = last_packet->ref_frames().back();
+    auto append_len = (const uint8_t *) sei_end - (const uint8_t *) sei_begin;
     INFOL("Modify SEI packet. seq=%d, size=%lu\n", last_packet->seq(), last_frame->size());
     INFOL("SEI data size=%lu\n", (uint8_t *) sei_end - (uint8_t *) sei_begin);
-    INFOL("SEI data: %s\n", ToHex((const uint8_t *) sei_begin, (uint8_t *) sei_end - (uint8_t *) sei_begin).c_str());
+    INFOL("SEI data: %s\n", ToHex((const uint8_t *) sei_begin, append_len).c_str());
+
+    if (last_frame->type() != Frame::kUDP) {
+        ERROL("Only support kUDP");
+        return;
+    }
+    auto &buf = last_frame->_data;
+
+    bool has_padding = last_packet->has_padding();
+    uint8_t padding_len = 0;
+    if (has_padding) {
+        // remove padding
+        padding_len = buf.back();
+        buf.resize(buf.size() - padding_len);
+    }
+    std::copy((uint8_t *) sei_begin, (uint8_t *) sei_end, std::back_inserter(buf));
+    if (has_padding) {
+        // append_len align 4 need (4 - append_len & 0x3)
+        // new_padding_len = (old_padding + append_len_align_len) %4
+        const uint8_t new_padding_len = ((4 - (append_len & 0x3)) + padding_len) % 4;
+        for (int i = 1; i < new_padding_len; ++i) { buf.push_back(0); }
+        buf.push_back(new_padding_len);
+    }
 }
 
 void
diff --git a/src/base/rtp_packet.cpp b/src/base/rtp_packet.cpp
index 2371a51..0e34a97 100644
--- a/src/base/rtp_packet.cpp
+++ b/src/base/rtp_packet.cpp
@@ -61,6 +61,12 @@ RTPPacket::packet_data() const
     return _rtp_ptr;
 }
 
+bool
+RTPPacket::has_padding() const
+{
+    return GetRTPPadding(_rtp_ptr);
+}
+
 uint8_t
 RTPPacket::payload_type() const
 {
diff --git a/src/base/rtp_packet.h b/src/base/rtp_packet.h
index 07b677b..61a314e 100644
--- a/src/base/rtp_packet.h
+++ b/src/base/rtp_packet.h
@@ -36,6 +36,7 @@ public:
     size_t rtp_payload_size();
 
     // rtp header, kMissPayload or kComplete
+    bool has_padding() const;
     uint8_t payload_type() const;
     uint16_t seq() const;
     uint32_t ssrc() const;
diff --git a/src/base/util.cpp b/src/base/util.cpp
index 1f91b0c..7bf8f93 100644
--- a/src/base/util.cpp
+++ b/src/base/util.cpp
@@ -11,6 +11,12 @@ GetRTPVersion(const uint8_t *data)
     return (data[0] & 0xC0) >> 6;
 }
 
+uint8_t
+GetRTPPadding(const uint8_t *header)
+{
+    return (header[0] & 0x20);
+}
+
 uint8_t
 GetRTPPayloadType(const uint8_t *data)
 {
diff --git a/src/base/util.h b/src/base/util.h
index 4bfb326..8e6dccf 100644
--- a/src/base/util.h
+++ b/src/base/util.h
@@ -10,6 +10,7 @@
 
 namespace sign {
 uint8_t GetRTPVersion(const uint8_t *header);
+uint8_t GetRTPPadding(const uint8_t *header);
 uint8_t GetRTPPayloadType(const uint8_t *header);
 uint16_t GetRTPSequenceNumber(const uint8_t *header);
 uint32_t GetRTPTimestamp(const uint8_t *header);