Add lerobot-preview-cameras for live camera feed preview

docs/source/cameras.mdx

@@ -22,7 +22,16 @@ Every camera requires a unique identifier to be instantiated, allowing you to di
 lerobot-find-cameras opencv # or realsense for Intel Realsense cameras
 ```
 
-The output will look something like this if you have two cameras connected:
+To view a **live preview** of each camera in separate windows:
+
+```bash
+lerobot-preview-cameras        # preview all detected OpenCV cameras
+lerobot-preview-cameras 0 1 2  # preview cameras at indices 0, 1, 2
+```
+
+Press `q` in any preview window to quit.
+
+The output of `lerobot-find-cameras` will look something like this if you have two cameras connected:
 
 ```bash
 --- Detected Cameras ---

pyproject.toml

@@ -125,6 +125,7 @@ intelrealsense = [
     "pyrealsense2>=2.55.1.6486,<2.57.0 ; sys_platform != 'darwin'",
     "pyrealsense2-macosx>=2.54,<2.55.0 ; sys_platform == 'darwin'",
 ]
+realsense-mesh = ["lerobot[intelrealsense]", "open3d>=0.18.0,<0.20.0"]
 phone = ["hebi-py>=2.8.0,<2.12.0", "teleop>=0.1.0,<0.2.0", "fastapi<1.0"]
 
 # Policies
@@ -198,6 +199,8 @@ all = [
 [project.scripts]
 lerobot-calibrate="lerobot.scripts.lerobot_calibrate:main"
 lerobot-find-cameras="lerobot.scripts.lerobot_find_cameras:main"
+lerobot-preview-cameras="lerobot.scripts.lerobot_preview_cameras:main"
+lerobot-realsense-mesh="lerobot.scripts.lerobot_realsense_mesh:main"
 lerobot-find-port="lerobot.scripts.lerobot_find_port:main"
 lerobot-record="lerobot.scripts.lerobot_record:main"
 lerobot-replay="lerobot.scripts.lerobot_replay:main"

src/lerobot/scripts/lerobot_preview_cameras.py

@@ -0,0 +1,109 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Live preview of camera feeds using OpenCV windows.
+
+Example:
+
+```shell
+# Preview all detected OpenCV cameras
+lerobot-preview-cameras
+
+# Preview specific camera indices
+lerobot-preview-cameras 0 1 2
+```
+"""
+
+import argparse
+import sys
+
+import cv2
+
+from lerobot.cameras.configs import ColorMode
+from lerobot.cameras.opencv.camera_opencv import OpenCVCamera
+from lerobot.cameras.opencv.configuration_opencv import OpenCVCameraConfig
+
+
+def preview_cameras(indices_or_paths: list[int | str]) -> None:
+    """Connect to each camera index/path and show live feed in separate windows."""
+    cameras: list[OpenCVCamera] = []
+    window_names: list[str] = []
+
+    try:
+        for idx in indices_or_paths:
+            config = OpenCVCameraConfig(
+                index_or_path=idx,
+                color_mode=ColorMode.RGB,
+            )
+            cam = OpenCVCamera(config)
+            cam.connect(warmup=True)
+            cameras.append(cam)
+            name = f"Camera {idx}"
+            window_names.append(name)
+            cv2.namedWindow(name, cv2.WINDOW_NORMAL)
+
+        print("Showing camera preview. Press 'q' in any window to quit.")
+        while True:
+            for i, (cam, name) in enumerate(zip(cameras, window_names)):
+                frame = cam.read()
+                if frame is None:
+                    continue
+                # OpenCV imshow expects BGR
+                bgr = cv2.cvtColor(frame, cv2.COLOR_RGB2BGR)
+                cv2.imshow(name, bgr)
+            if cv2.waitKey(1) & 0xFF == ord("q"):
+                break
+    finally:
+        for name in window_names:
+            cv2.destroyWindow(name)
+        for cam in cameras:
+            if cam.is_connected:
+                cam.disconnect()
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Live preview of OpenCV camera feeds in separate windows.",
+    )
+    parser.add_argument(
+        "indices",
+        type=int,
+        nargs="*",
+        help="Camera indices to preview (e.g. 0 1 2). If omitted, discovers and previews all OpenCV cameras.",
+    )
+    args = parser.parse_args()
+
+    if args.indices:
+        indices = args.indices
+    else:
+        # Discover all OpenCV cameras
+        try:
+            found = OpenCVCamera.find_cameras()
+        except Exception as e:
+            print(f"Error discovering cameras: {e}", file=sys.stderr)
+            sys.exit(1)
+        if not found:
+            print("No OpenCV cameras detected. Try: lerobot-find-cameras opencv", file=sys.stderr)
+            sys.exit(1)
+        indices = [c["id"] for c in found]
+        print(f"Previewing cameras: {indices}")
+
+    preview_cameras(indices)
+
+
+if __name__ == "__main__":
+    main()