usb_cam
A ROS Driver for V4L USB Cameras
Links
README
usb_cam 
A ROS 2 Driver for V4L USB Cameras
This package is based off of V4L devices specifically instead of just UVC.
For ros1 documentation, see the ROS wiki.
Supported ROS 2 Distros and Platforms
All Officially supported Linux Distros and corresponding ROS 2 releases are supported. Please create an issue if you experience any problems on these platforms.
Windows: TBD/Untested/Unproven MacOS: TBD/Untested/Unproven
For either MacOS or Windows - if you would like to try and get it working please create an issue to document your effort. If it works we can add it to the instructions here!
Quickstart
Assuming you have a supported ROS 2 distro installed, run the following command to install the binary release:
sudo apt-get install ros-<ros2-distro>-usb-cam
As of today this package should be available for binary installation on all active ROS 2 distros.
If for some reason you cannot install the binaries, follow the directions below to compile from source.
Building from Source
Clone/Download the source code into your workspace:
cd /path/to/colcon_ws/src
git clone https://github.com/ros-drivers/usb_cam.git
Or click on the green “Download zip” button on the repo’s github webpage.
Once downloaded and ensuring you have sourced your ROS 2 underlay, go ahead and install the dependencies:
cd /path/to/colcon_ws
rosdep install --from-paths src --ignore-src -y
From there you should have all the necessary dependencies installed to compile the usb_cam package:
cd /path/to/colcon_ws
colcon build
source /path/to/colcon_ws/install/setup.bash
Be sure to source the newly built packages after a successful build.
Once sourced, you should be able to run the package in one of three ways, shown in the next section.
Running
The usb_cam_node can be ran with default settings, by setting specific parameters either via the command line or by loading in a parameters file.
We provide a “default” params file in the usb_cam/config/params.yaml directory to get you started. Feel free to modify this file as you wish.
Also provided is a launch file that should launch the usb_cam_node_exe executable along with an additional node that displays an image topic.
The commands to run each of these different ways of starting the node are shown below:
NOTE: you only need to run ONE of the commands below to run the node
# run the executable with default settings (without params file)
ros2 run usb_cam usb_cam_node_exe
# run the executable while passing in parameters via a yaml file
ros2 run usb_cam usb_cam_node_exe --ros-args --params-file /path/to/colcon_ws/src/usb_cam/config/params.yaml
# launch the usb_cam executable that loads parameters from the same `usb_cam/config/params.yaml` file as above
# along with an additional image viewer node
ros2 launch usb_cam camera.launch.py
Launching Multiple usb_cam’s
To launch multiple nodes at once, simply remap the namespace of each one:
ros2 run usb_cam usb_cam_node_exe --remap __ns:=/usb_cam_0 --params-file /path/to/usb_cam/config/params_0.yaml
ros2 run usb_cam usb_cam_node_exe --remap __ns:=/usb_cam_1 --params-file /path/to/usb_cam/config/params_1.yaml
Supported formats
Device supported formats
To see a connected devices supported formats, run the usb_cam_node and observe the console output.
An example output is:
This devices supproted formats:
Motion-JPEG: 1280 x 720 (30 Hz)
Motion-JPEG: 960 x 540 (30 Hz)
Motion-JPEG: 848 x 480 (30 Hz)
Motion-JPEG: 640 x 480 (30 Hz)
Motion-JPEG: 640 x 360 (30 Hz)
YUYV 4:2:2: 640 x 480 (30 Hz)
YUYV 4:2:2: 1280 x 720 (10 Hz)
YUYV 4:2:2: 640 x 360 (30 Hz)
YUYV 4:2:2: 424 x 240 (30 Hz)
YUYV 4:2:2: 320 x 240 (30 Hz)
YUYV 4:2:2: 320 x 180 (30 Hz)
YUYV 4:2:2: 160 x 120 (30 Hz)
Driver supported formats
The driver has its own supported formats. See the source code for details.
After observing the devices supported formats, specify which
format to use via the parameters file with the pixel_format parameter.
To see a list of all currently supported driver formats, run the following command:
ros2 run usb_cam usb_cam_node_exe --ros-args -p pixel_format:="test"
Note: “test” here could be replaced with any non-supported pixel format string. The driver will detect if the given pixel format is supported or not.
More formats and conversions can be added, contributions welcome!
Supported IO methods
This driver supports three different IO methods as of today:
read: copies the video frame between user and kernal spacemmap: memory mapped buffers allocated in kernel spaceuserptr: memory buffers allocated in the user space
To read more on the different methods, check out this article that provides a good overview of each
Compression
Big thanks to the ros2_v4l2_camera package and their documentation on this topic.
The usb_cam should support compression by default since it uses image_transport to publish its images as long as the image_transport_plugins package is installed on your system. With the plugins installed the usb_cam package should publish a compressed topic automatically.
Unfortunately rviz2 and show_image.py do not support visualizing the compressed images just yet so you will need to republish the compressed image downstream to uncompress it:
ros2 run image_transport republish compressed raw --ros-args --remap in/compressed:=image_raw/compressed --remap out:=image_raw/uncompressed
Address and leak sanitizing
Incorporated into the CMakelists.txt file to assist with memory leak and address sanitizing
is a flag to add these compile commands to the targets.
To enable them, pass in the SANITIZE=1 flag:
colcon build --packages-select usb_cam --cmake-args -DSANITIZE=1
Once built, run the nodes executable directly and pass any ASAN_OPTIONS that are needed:
ASAN_OPTIONS=new_delete_type_mismatch=0 ./install/usb_cam/lib/usb_cam/usb_cam_node_exe
After shutting down the executable with Ctrl+C, the sanitizer will report any memory leaks.
By default this is turned off since compiling with the sanatizer turned on causes bloat and slows down performance.
Documentation
Doxygen files can be found on the ROS wiki.
License
usb_cam is released with a BSD license. For full terms and conditions, see the LICENSE file.