Fix LoadStreams final frame bug (#4387)

Co-authored-by: Nadim Bou Alwan <64587372+nadinator@users.noreply.github.com>

ultralytics/data/converter.py

@@ -36,11 +36,12 @@ def convert_coco(labels_dir='../coco/annotations/', use_segments=False, use_keyp
         use_keypoints (bool, optional): Whether to include keypoint annotations in the output.
         cls91to80 (bool, optional): Whether to map 91 COCO class IDs to the corresponding 80 COCO class IDs.
 
-    Raises:
-        FileNotFoundError: If the labels_dir path does not exist.
+    Example:
+        ```python
+        from ultralytics.data.converter import convert_coco
 
-    Example Usage:
-        convert_coco(labels_dir='../coco/annotations/', use_segments=True, use_keypoints=True, cls91to80=True)
+        convert_coco('../datasets/coco/annotations/', use_segments=True, use_keypoints=False, cls91to80=True)
+        ```
 
     Output:
         Generates output files in the specified output directory.

ultralytics/data/loaders.py

@@ -79,19 +79,18 @@ class LoadStreams:
     def update(self, i, cap, stream):
         """Read stream `i` frames in daemon thread."""
         n, f = 0, self.frames[i]  # frame number, frame array
-        while self.running and cap.isOpened() and n < f:
+        while self.running and cap.isOpened() and n < (f - 1):
             # Only read a new frame if the buffer is empty
             if not self.imgs[i]:
                 n += 1
                 cap.grab()  # .read() = .grab() followed by .retrieve()
                 if n % self.vid_stride == 0:
                     success, im = cap.retrieve()
-                    if success:
-                        self.imgs[i].append(im)  # add image to buffer
-                    else:
+                    if not success:
+                        im = np.zeros(self.shape[i], dtype=np.uint8)
                         LOGGER.warning('WARNING ⚠️ Video stream unresponsive, please check your IP camera connection.')
-                        self.imgs[i].append(np.zeros(self.shape[i]))
                         cap.open(stream)  # re-open stream if signal was lost
+                    self.imgs[i].append(im)  # add image to buffer
             else:
                 time.sleep(0.01)  # wait until the buffer is empty