disappeared object appears in fresh trai

app.py

@@ -131,10 +131,12 @@ def format_points_list(points, is_video=False):
     return "[" + ", ".join(rows) + "]"
 
 
-def _interpolate_keyframes(keyframes, total_frames):
+def _interpolate_keyframes(keyframes, total_frames, max_gap=None):
     """Linearly interpolate positions between keyframes.
 
     keyframes: sorted list of (frame_idx, x, y)
+    max_gap: if set, skip interpolation (leave gap invisible) when two keyframes
+             are more than this many frames apart.
     Returns dict {frame_idx: (x, y)} for every frame from first to last keyframe.
     """
     if not keyframes:
@@ -146,7 +148,7 @@ def _interpolate_keyframes(keyframes, total_frames):
         if i + 1 < len(keyframes):
             nf, nx, ny = keyframes[i + 1]
             span = nf - f_idx
-            if span > 1:
+            if span > 1 and (max_gap is None or span <= max_gap):
                 for t in range(1, span):
                     alpha = t / span
                     positions[f_idx + t] = (x + alpha * (nx - x), y + alpha * (ny - y))
@@ -178,9 +180,10 @@ def create_annotated_video(video_path, points, metadata, tracking):
     total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
     obj_positions = {}
     obj_keyframe_set = {}
+    max_gap_frames = int(fps)  # gaps > 1 second: no interpolation, object disappears
     for obj_id, kfs in obj_keyframes.items():
         kfs.sort(key=lambda k: k[0])
-        obj_positions[obj_id] = _interpolate_keyframes(kfs, total_frames)
+        obj_positions[obj_id] = _interpolate_keyframes(kfs, total_frames, max_gap=max_gap_frames)
         raw_kf = set(f_idx for f_idx, _, _ in kfs)
         obj_keyframe_set[obj_id] = set(
             f for kf in raw_kf for f in range(kf - KEYFRAME_HOLD_FRAMES, kf + KEYFRAME_HOLD_FRAMES + 1)
@@ -203,6 +206,9 @@ def create_annotated_video(video_path, points, metadata, tracking):
         for obj_id, positions in obj_positions.items():
             if current_frame in positions:
                 px, py = positions[current_frame]
+                # Clear trail if the object was absent in the previous frame (gap reappearance)
+                if current_frame > 0 and (current_frame - 1) not in positions:
+                    obj_history[obj_id] = []
                 obj_history[obj_id].append((px, py))
                 if len(obj_history[obj_id]) > trail_length:
                     obj_history[obj_id] = obj_history[obj_id][-trail_length:]