v4l2_camera

A ROS 2 camera driver using Video4Linux2 (V4L2).

Custom Dependencies

The following dependencies need to be pulled in manually, because we need new features in them that have not been released yet:

• common_interfaces - USB cameras mostly use the YUY2 format, which historically hasn’t been supported in ROS. Support has landed recently, but has not been released yet, so you need to clone master into your workspace:

    git clone https://github.com/ros2/common_interfaces.git src/common_interfaces
  

• vision_opencv - The OpenCV bridge is used to convert between image formats. Support for the YUY2 format has not landed yet (see PR ros-perception/vision_opencv#309. Until that has happened, clone the fork into your workspace:

    git clone --branch yuv422-yuy2 https://github.com/sgvandijk/vision_opencv.git src/vision_opencv
  

Nodes

v4l2_camera_node

The v4l2_camera_node interfaces with standard V4L2 devices and publishes images as sensor_msgs/Image messages.

Published Topics

• /image_raw - sensor_msgs/Image

  The image.

Parameters

• video_device - string, default: "/dev/video0"

  The device the camera is on.

• pixel_format - string, default: "YUYV"

  The pixel format to request from the camera. Must be a valid four character ‘FOURCC’ code supported by V4L2 and by your camera. The node outputs the available formats supported by your camera when started.

  Currently only "YUYV" is supported, which results in image messages with the YUV422_YUY2 encoding.

• output_encoding - string, default: "rgb8"

  The encoding to use for the output image. Any format supported by cv_bridge::cvtColor is allowed. If this matches the input format from the camera, no conversion and thus no additional overhead is required.

• image_size - integer_array, default: [640, 480]

  Width and height of the image.

• Camera Control Parameters

  Camera controls, such as brightness, contrast, white balance, etc, are automatically made available as parameters. The driver node enumerates all controls, and creates a parameter for each, with the corresponding value type. The parameter name is derived from the control name reported by the camera driver, made lower case, commas removed, and spaces replaced by underscores. So Brightness becomes brightness, and White Balance, Automatic becomes white_balance_automatic.

Compressed Transport

Streaming raw images from a robot to your machine takes up a very large bandwidth and is especially not feasible through WiFi. By using image_transport the images can be compressed to make streaming possible. However, by default image_transport only supports raw transfer, and additional plugins are required to enable compression.

Standard ones are available in the image_transport_plugins repository. You can clone these into your workspace to get these:

git clone --branch ros2 https://github.com/ros-perception/image_transport_plugins.git src/image_transport_plugins

Building: Ubuntu

The following packages are required to be able to build the plugins:

sudo apt install libtheora-dev libogg-dev libboost-python-dev

Building: Arch

To get the plugins compiled on Arch Linux, a few special steps are

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