diff --git a/src/zm_event.cpp b/src/zm_event.cpp
index 109df5dd3..e564479f3 100644
--- a/src/zm_event.cpp
+++ b/src/zm_event.cpp
@@ -256,6 +256,20 @@ Event::~Event() {
   if ( frame_data.size() )
     WriteDbFrames();
 
+  // update frame deltas to refer to video start time which may be a few frames before event start
+  struct timeval video_offset = {0};
+  struct timeval video_start_time  = monitor->GetVideoWriterStartTime();
+  if (video_start_time.tv_sec > 0) {
+     timersub(&video_start_time, &start_time, &video_offset);
+     Debug(1, "Updating frames delta by %d sec %d usec",
+           video_offset.tv_sec, video_offset.tv_usec);
+     UpdateFramesDelta(video_offset.tv_sec + video_offset.tv_usec*1e-6);
+  }
+  else {
+     Debug(3, "Video start_time %d sec %d usec not valid -- frame deltas not updated",
+           video_start_time.tv_sec, video_start_time.tv_usec);
+  }
+
   // Should not be static because we might be multi-threaded
   char sql[ZM_SQL_LGE_BUFSIZ];
   snprintf(sql, sizeof(sql), 
@@ -554,6 +568,27 @@ void Event::WriteDbFrames() {
   db_mutex.unlock();
 } // end void Event::WriteDbFrames()
 
+// Subtract an offset time from frames deltas to match with video start time
+void Event::UpdateFramesDelta(double offset) {
+  char sql[ZM_SQL_MED_BUFSIZ];
+
+  if (offset == 0.0) return;
+  // the table is set to auto update timestamp so we force it to keep current value
+  snprintf(sql, sizeof(sql),
+    "UPDATE Frames SET timestamp = timestamp, Delta = Delta - (%.4f) WHERE EventId = %" PRIu64,
+    offset, id);
+
+  db_mutex.lock();
+  if (mysql_query(&dbconn, sql)) {
+    db_mutex.unlock();
+    Error("Can't update frames: %s, sql was %s", mysql_error(&dbconn), sql);
+    return;
+  }
+  db_mutex.unlock();
+  Info("Updating frames delta by %0.2f sec to match video file", offset);
+}
+
+
 void Event::AddFrame(Image *image, struct timeval timestamp, int score, Image *alarm_image) {
   if ( !timestamp.tv_sec ) {
     Debug(1, "Not adding new frame, zero timestamp");
diff --git a/src/zm_event.h b/src/zm_event.h
index 2035b6af6..77199509c 100644
--- a/src/zm_event.h
+++ b/src/zm_event.h
@@ -132,6 +132,7 @@ class Event {
   private:
     void AddFramesInternal( int n_frames, int start_frame, Image **images, struct timeval **timestamps );
     void WriteDbFrames();
+    void UpdateFramesDelta(double offset);
 
   public:
     static const char *getSubPath( struct tm *time ) {
diff --git a/src/zm_ffmpeg_camera.cpp b/src/zm_ffmpeg_camera.cpp
index 029a2de0d..ef4dfc057 100644
--- a/src/zm_ffmpeg_camera.cpp
+++ b/src/zm_ffmpeg_camera.cpp
@@ -872,6 +872,7 @@ int FfmpegCamera::CaptureAndRecord(
           // since the last keyframe.
           unsigned int packet_count = 0;
           ZMPacket *queued_packet;
+          struct timeval video_offset = {0};
 
           // Clear all packets that predate the moment when the recording began
           packetqueue->clear_unwanted_packets(
@@ -880,6 +881,14 @@ int FfmpegCamera::CaptureAndRecord(
           while ( (queued_packet = packetqueue->popPacket()) ) {
             AVPacket *avp = queued_packet->av_packet();
 
+            // compute time offset between event start and first frame in video
+            if (packet_count == 0){
+                monitor->SetVideoWriterStartTime(queued_packet->timestamp);
+                timersub(&queued_packet->timestamp, &recording, &video_offset);
+                Info("Event video offset is %.3f sec (<0 means video starts early)",
+                     video_offset.tv_sec + video_offset.tv_usec*1e-6);
+            }
+
             packet_count += 1;
             // Write the packet to our video store
             Debug(2, "Writing queued packet stream: %d  KEY %d, remaining (%d)",
diff --git a/src/zm_monitor.h b/src/zm_monitor.h
index 97f173845..9109c9c72 100644
--- a/src/zm_monitor.h
+++ b/src/zm_monitor.h
@@ -466,6 +466,8 @@ public:
   const std::vector<EncoderParameter_t>* GetOptEncoderParams() const { return &encoderparamsvec; }
   uint64_t GetVideoWriterEventId() const { return video_store_data->current_event; }
   void SetVideoWriterEventId( unsigned long long p_event_id ) { video_store_data->current_event = p_event_id; }
+  struct timeval GetVideoWriterStartTime() const { return video_store_data->recording; }
+  void SetVideoWriterStartTime(struct timeval &t) { video_store_data->recording = t; }
  
   unsigned int GetPreEventCount() const { return pre_event_count; };
   struct timeval GetVideoBufferDuration() const { return video_buffer_duration; };