diff --git a/Pose2Sim/poseEstimation.py b/Pose2Sim/poseEstimation.py
index e59b057..2d83964 100644
--- a/Pose2Sim/poseEstimation.py
+++ b/Pose2Sim/poseEstimation.py
@@ -99,6 +99,34 @@ def save_to_openpose(json_file_path, keypoints, scores):
         json.dump(json_output, json_file)
 
 
+def sort_people_rtmlib(pose_tracker, keypoints, scores):
+    '''
+    Associate persons across frames (RTMLib method)
+
+    INPUTS:
+    - pose_tracker: PoseTracker. The initialized RTMLib pose tracker object
+    - keypoints: array of shape K, L, M with K the number of detected persons,
+    L the number of detected keypoints, M their 2D coordinates
+    - scores: array of shape K, L with K the number of detected persons,
+    L the confidence of detected keypoints
+
+    OUTPUT:
+    - sorted_keypoints: array with reordered persons
+    - sorted_scores: array with reordered scores
+    '''
+    
+    try:
+        desired_size = max(pose_tracker.track_ids_last_frame)+1
+        sorted_keypoints = np.full((desired_size, keypoints.shape[1], 2), np.nan)
+        sorted_keypoints[pose_tracker.track_ids_last_frame] = keypoints[:len(pose_tracker.track_ids_last_frame), :, :]
+        sorted_scores = np.full((desired_size, scores.shape[1]), np.nan)
+        sorted_scores[pose_tracker.track_ids_last_frame] = scores[:len(pose_tracker.track_ids_last_frame), :]
+    except:
+        sorted_keypoints, sorted_scores = keypoints, scores
+
+    return sorted_keypoints, sorted_scores
+
+
 def process_video(video_path, pose_tracker, tracking, output_format, save_video, save_images, display_detection, frame_range):
     '''
     Estimate pose from a video file
@@ -160,14 +188,7 @@ def process_video(video_path, pose_tracker, tracking, output_format, save_video,
 
                 # Reorder keypoints, scores
                 if tracking:
-                    max_id = max(pose_tracker.track_ids_last_frame)
-                    num_frames, num_points, num_coordinates = keypoints.shape
-                    keypoints_filled = np.zeros((max_id+1, num_points, num_coordinates))
-                    scores_filled = np.zeros((max_id+1, num_points))
-                    keypoints_filled[pose_tracker.track_ids_last_frame] = keypoints
-                    scores_filled[pose_tracker.track_ids_last_frame] = scores
-                    keypoints = keypoints_filled
-                    scores = scores_filled
+                    keypoints, scores = sort_people_rtmlib(pose_tracker, keypoints, scores)
 
                 # Save to json
                 if 'openpose' in output_format: