4.1. Mono Camera Tools and Capture Node

4.1.1. Mono Camera Tools

Camera Calibration: A Python tool for camera calibration is provided: $SDK_DIR/tools/mono_camera/camera_calibration.py. This tool calibrates the camera using a set of checkerboard images captured with the target USB camera and generates a camera_info.yaml file. Example calibration images are provided. While setting up the Docker environment, the calibration images are downloaded under $HOME/j7ros_home/data/calib_images. Below is the usage of the camera calibration tool.

usage: camera_calibration.py [-h] [-p PATH] [-e EXT] [-r PTS_ROWS] [-c PTS_COLUMNS] [-s SQUARE_SIZE] [-v VISUALIZE] [-f SCALING_FACTOR] [-o OUT_FNAME] [-n CAMERA_NAME]

optional arguments:
-h, --help            show this help message and exit
-p PATH, --path PATH  Path to the directory storing images for calibration
-e EXT, --ext EXT     Extension of the files
-r PTS_ROWS, --pts_rows PTS_ROWS
                        Number of inner corners per row
-c PTS_COLUMNS, --pts_columns PTS_COLUMNS
                        Number of inner corners per column
-s SQUARE_SIZE, --square_size SQUARE_SIZE
                        Size of a square (the edge, by mm) of the checker board
-v VISUALIZE, --visualize VISUALIZE
                        Visualize the checker board or not
-f SCALING_FACTOR, --scaling_factor SCALING_FACTOR
                        scaling factor after reading images
-o OUT_FNAME, --out_fname OUT_FNAME
                        Path to the output file to store result (in YAML format)
-n CAMERA_NAME, --camera_name CAMERA_NAME
                        Camera name

For examples of how to use the tool, please refer to $SDK_DIR/tools/mono_camera/calib_C920.sh.

Rectification Map Generation: A Python tool is provided for generating rectification map: $SDK_DIR/tools/mono_camera/generate_rect_map_mono.py. This tool takes the camera_info YAML file as input and generates a binary file for undistortion/rectification look-up-table (LUT). The generated LUT is required for offloading the undistortion/rectification processes to the VPAC/LDC hardware accelerator. Below is the usage of the tool.
```
usage: generate_rect_map_mono.py [-h] [--input INPUT] [--name NAME]

optional arguments:
-h, --help            show this help message and exit
--input INPUT, -i INPUT
                        YAML file name for camera_info. The file should be stored under ../config folder
--name NAME, -n NAME  Camera name
```
For examples of how to use the tool, please see $SDK_DIR/tools/mono_camera/calib_C920.sh.

4.1.2. USB Mono Camera ROS Node

This is a ROS node for USB mono cameras (Webcam) based on the OpenCV VideoCapture API. The node publishes raw images and camera information.

Note

This ROS node has only been tested with Logitech C920 and C270 webcams in ‘YUYV’ (YUYV 4:2:2) mode. ‘MJPG’ (Motion-JPEG) mode is currently not enabled or tested. If you want to use the camera in ‘MJPG’ mode, it is recommended to use the gscam / gscam2 ROS package instead.

4.1.2.1. Usage

Build the USB mono camera ROS node

cd $ROS_WS
# ROS 1
catkin_make --source /opt/robotics_sdk/ros1 --force-cmake
source devel/setup.bash
# ROS 2
colcon build --base-paths /opt/robotics_sdk/ros2 --cmake-force-configure
source install/setup.bash

Launch the mono camera node

# ROS 1
roslaunch mono_capture mono_capture.launch
# ROS 2
ros2 launch mono_capture mono_capture_launch.py

4.1.2.2. Launch File Parameters

Parameter	Description	Value
model_str	Camera model string	string
cam_id	Camera ID number. Set `cam_id = X` if the device shows up as `/dev/video-usb-camX` on the target with TI Edge AI	string
camera_mode	Camera mode	‘FHD’ (1920x1080)
		‘HD’ (1280x720)
		‘VGA’ (640x480)
frame_rate	Frame rate at which raw images are published	int
encoding	Image encoding	‘yuv422’ (default) or ‘bgr8’
topic_ns	Topic namespace	‘camera’ (default)

Note

When encoding is set to ‘yuv422’, the pixel format YUV422::YUYV from the webcam is converted to YUV422::UYVY format to ensure compatibility with the LDC hardware accelerator.