diff --git a/algorithm/mot/sv_mot.cpp b/algorithm/mot/sv_mot.cpp
index 609cc07..73701c3 100644
--- a/algorithm/mot/sv_mot.cpp
+++ b/algorithm/mot/sv_mot.cpp
@@ -195,6 +195,8 @@ void SORT::update(TargetsInFrame& tgts)
             tracklet.age = 0;
             tracklet.hits = 1;
             tracklet.misses = 0;
+            tracklet.frame_id=tgts.frame_id;
+            tracklet.tentative = true;
             // initate the motion
             pair<Matrix<double, 8, 1>, Matrix<double, 8, 8> > motion = kf.initiate(tracklet.bbox);
             tracklet.mean = motion.first;
@@ -243,12 +245,13 @@ void SORT::update(TargetsInFrame& tgts)
             int detectionIndex = match.second;
             if (trackletIndex >= 0 && detectionIndex >= 0)
             {
-                if (iouMatrix[match.first][match.second] >= 0)
+                if (iouMatrix[match.first][match.second] >= _iou_threshold)//iou_thrshold
                 {
                     sv::Box box;
                     tgts.targets[detectionIndex].getBox(box);
                     this->_tracklets[trackletIndex].age = 0;
                     this->_tracklets[trackletIndex].hits++;
+                    this->_tracklets[trackletIndex].frame_id=tgts.frame_id;
                     this->_tracklets[trackletIndex].bbox << box.x1, box.y1, box.x2-box.x1, box.y2-box.y1;
 
                     auto[mean, covariance] = kf.update(this->_tracklets[trackletIndex].mean, this->_tracklets[trackletIndex].covariance, box);
@@ -274,6 +277,8 @@ void SORT::update(TargetsInFrame& tgts)
                 tracklet.age = 0;
                 tracklet.hits = 1;
                 tracklet.misses = 0;
+                tracklet.frame_id=tgts.frame_id;
+                tracklet.tentative = true;
                 
                 auto[new_mean, new_covariance] = kf.initiate(tracklet.bbox);
                 tracklet.mean = new_mean;
@@ -284,6 +289,19 @@ void SORT::update(TargetsInFrame& tgts)
                 this->_tracklets.push_back(tracklet);
             }
         }
+        for (auto& tracklet : this->_tracklets)
+        {
+            if (tracklet.hits >= _min_hits)
+            {
+                tracklet.tentative = false;
+            }
+            if ((tgts.frame_id-tracklet.frame_id <= _max_age) || (!tracklet.tentative && tracklet.frame_id==tgts.frame_id))
+            {
+                _new_tracklets.push_back(tracklet);
+            } 
+        }
+        _tracklets = _new_tracklets;
+        std::vector <Tracklet> ().swap(_new_tracklets);
     }
 }
 
diff --git a/include/sv_mot.h b/include/sv_mot.h
index 105ab59..54964bf 100644
--- a/include/sv_mot.h
+++ b/include/sv_mot.h
@@ -55,6 +55,8 @@ public:
     int age;
     int hits;
     int misses;
+    int frame_id=0;
+    bool tentative;
     std::vector<double> features;
     Eigen::Matrix<double, 8, 1> mean;
     Eigen::Matrix<double, 8, 8> covariance;
@@ -93,6 +95,7 @@ private:
     int _min_hits;
     int _next_tracklet_id;
     std::vector <Tracklet> _tracklets;
+    std::vector <Tracklet> _new_tracklets;
 };