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Using v4l2_camera package

In Ubuntu 22.04 for ROS-humble

Installation

sudo apt install ros-${ROS_DISTRO}-v4l2-camera

Parameter files

Run v4l2_camera, and dump the parameters in yaml file like ...

ros2 run v4l2_camera v4l2_camera_node

ros2 param dump /v4l2_camera > <path_to_yaml_file>

Parameter file example

/**:
  ros__parameters:
    image_size:
      - 640
      - 480
    output_encoding: bgr8
    camera_frame_id: camera_optical_frame
    qos_overrides:
      /parameter_events:
        publisher:
          depth: 1000
          durability: volatile
          history: keep_last
          reliability: reliable
    use_sim_time: false
    video_device: /dev/video2   # Change according to your device id
    camera_info_url: "package://silo/config/c270.yaml"

Camera info file example

image_width: 640
image_height: 480
camera_name: c270
camera_matrix:
  rows: 3
  cols: 3
  data: [720.8, 0.000000, 290.67425, 0.000000, 713.35, 195.11265, 0.000000, 0.000000, 1.000000]
distortion_model: plumb_bob
distortion_coefficients:
  rows: 1
  cols: 5
  data: [0.0126, 0.8867, 0.0030, 0.0001507, -3.0664] # [k1, k2, t1, t2, k3]
rectification_matrix:
  rows: 3
  cols: 3
  data: [1.000, 0.00, 0.00, 0.00, 1.000, 0.00, 0.00, 0.00, 1.00]
projection_matrix:
  rows: 3
  cols: 4
  data: [720.8, 0.000000, 290.67425, 0.000000, 0.000000, 713.35, 195.11265, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000]

Running node

ros2 run v4l2_camera v4l2_camera_node --ros-args --params-file <path_to_parameter_file>

Pitfalls encountered

  1. Camera_info file should have all the elements as shown in example. Missing any one (except camera_name) results in error.
  2. Incorrect format for camera_info_url
    If camera_info file inside a ros2 package: 
    camera_info_url: 'package://<package_name>/<path_to_camera_info_file>'
    If camera_info file is given as file system path: 
    camera_info_url: 'file://<absolute_path_to_camera_info_file>
    Do not forget to add 'file://...' before giving absolute path

Why I used <v4l2> instead of <usb_cam>?

Although usb_cam has good documentation and more customization options in parameters files. It doesnot support bgr output encoding natively. And, bgr is default encoding of opencv package.

Reference

  1. Official repo: gitlab_link
  2. For camera_info file: usb_cam package