LiveKit Portal for ROS composition

Overview

The LiveKit Portal for ROS can run as a ROS 2 component  inside a component container, a process that loads and runs several nodes. This setup is called composition. Nodes in the same container can exchange messages through intra-process communication instead of the ROS middleware,so the portal can receive high-bandwidth topics such as camera images, point clouds, and other large data types without serializing them.

The package exports the ros_portal::RosPortal component. Composition requires v0.3.0  or later of LiveKit Portal for ROS.

Add the portal to your ComposableNodeContainer

Add a ComposableNode for ros_portal::RosPortal to the container that runs your other nodes. Use a single-threaded container such as component_container:

from launch_ros.actions import ComposableNodeContainer
from launch_ros.descriptions import ComposableNode

container = ComposableNodeContainer(
    name='robot_container',
    namespace='',
    package='rclcpp_components',
    executable='component_container',
    composable_node_descriptions=[
        ComposableNode(
            package='ros_portal',
            plugin='ros_portal::RosPortal',
            name='ros_portal',
            parameters=[{'config_path': '/path/to/config.yaml'}],
        ),
        # Add other composable nodes here
    ],
)

In composition, the container owns the executor, so the node ignores the ros_threads configuration field. If the configuration is invalid or LiveKit fails to initialize, the component fails to load and the container logs the error.

Intra-process communication

Intra-process communication reduces transport overhead and latency for high-bandwidth topics, such as camera images. To use intra-process communication, all of the following must be true:

• The ROS Portal and its peer nodes run in the same process and have the same ROS context.
• The ROS Portal and its peer nodes enable use_intra_process_comms.
• The publishers and subscriptions use compatible QoS.

Enable intra-process communication in each ComposableNode description:

extra_arguments=[{'use_intra_process_comms': True}],

How a producer publishes affects whether ROS copies the message before the ROS Portal receives it. Both styles forward the topic. Only the copy differs.

Intra-process communication has the following limitations:

• Intra-process communication reduces ROS delivery overhead only. Video encoding, decoding, and LiveKit networking still copy data.
• The ROS Portal republishes inbound LiveKit video as sensor_msgs/CompressedImage, and ROS copies it to local subscribers.
• On Jazzy, generic serialized topics don't use rclcpp intra-process delivery.
• Only one ROS Portal can be loaded in a process.

Additional resources

The following resource provides more information about running LiveKit Portal for ROS.