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5.2.3. Multi-Camera Synchronization Verification Node

File path: image_sync_example_node.cpp

This example node is designed for synchronized capture and timestamp verification across four Orbbec cameras. It can be used to validate frame alignment accuracy under the multi-camera Primary / Secondary Synced mode.

5.2.3.1. Usage Guide

  1. Modify multi_camera_synced.launch as follows

    • Add include blocks to support four cameras.

    • Select the appropriate launch file based on your camera model. For example, use gemini_330_series.launch for the Gemini 330 series.

    • Naming convention: camera_name should follow the format camera_01, camera_02, camera_03, …

    • Set device_num to 4.

    • Configure the USB ports using:

      rosrun orbbec_camera list_devices_node

      to view and bind the correct ports.

    • Set synchronization mode to Primary/Secondary Synced, with one camera as primary and the others as secondary_synced.

    • Startup sequence: Start secondary cameras first, and start the Primary camera last to ensure the synchronization signal is established correctly.

  1. Modify configuration files

    Edit the following two files under the config directory:

    • camera_params.yaml

    • camera_secondary_params.yaml

    Ensure the following settings are consistent across all cameras:

    • Enable both depth and color streams.

    • Use the same frame rate (fps) for all cameras.

  1. Launch and Verification

    • Start the multi-camera synchronization launch file:

      roslaunch orbbec_camera multi_camera_synced.launch

    • In a new terminal, run the synchronization verification node:

      rosrun orbbec_camera image_sync_example_node

      This node outputs timestamp differences between multiple camera streams for synchronization validation.

  1. Reference Launch File

<launch>
  <arg name="device_num" default="4"/>

  <arg name="camera1_name" default="camera_01"/>
  <arg name="camera2_name" default="camera_02"/>
  <arg name="camera3_name" default="camera_03"/>
  <arg name="camera4_name" default="camera_04"/>

  <arg name="camera1_usb_port" default="2-2.3"/>
  <arg name="camera2_usb_port" default="2-1"/>
  <arg name="camera3_usb_port" default="2-3"/>
  <arg name="camera4_usb_port" default="2-4"/>

  <arg name="primary_config" default="$(find orbbec_camera)/config/camera_params.yaml"/>
  <arg name="secondary_config" default="$(find orbbec_camera)/config/camera_secondary_params.yaml"/>

  <!-- secondary cameras -->
  <include file="$(find orbbec_camera)/launch/gemini_330_series.launch">
    <arg name="camera_name" value="$(arg camera2_name)"/>
    <arg name="usb_port" value="$(arg camera2_usb_port)"/>
    <arg name="device_num" value="$(arg device_num)"/>
    <arg name="sync_mode" value="secondary_synced"/>
    <arg name="config_file_path" value="$(arg secondary_config)"/>
    <arg name="trigger_out_enabled" value="false"/>
  </include>

  <include file="$(find orbbec_camera)/launch/gemini_330_series.launch">
    <arg name="camera_name" value="$(arg camera3_name)"/>
    <arg name="usb_port" value="$(arg camera3_usb_port)"/>
    <arg name="device_num" value="$(arg device_num)"/>
    <arg name="sync_mode" value="secondary_synced"/>
    <arg name="config_file_path" value="$(arg secondary_config)"/>
    <arg name="trigger_out_enabled" value="false"/>
  </include>

  <include file="$(find orbbec_camera)/launch/gemini_330_series.launch">
    <arg name="camera_name" value="$(arg camera4_name)"/>
    <arg name="usb_port" value="$(arg camera4_usb_port)"/>
    <arg name="device_num" value="$(arg device_num)"/>
    <arg name="sync_mode" value="secondary_synced"/>
    <arg name="config_file_path" value="$(arg secondary_config)"/>
    <arg name="trigger_out_enabled" value="false"/>
  </include>

  <!-- primary camera -->
  <include file="$(find orbbec_camera)/launch/gemini_330_series.launch">
    <arg name="camera_name" value="$(arg camera1_name)"/>
    <arg name="usb_port" value="$(arg camera1_usb_port)"/>
    <arg name="device_num" value="$(arg device_num)"/>
    <arg name="sync_mode" value="primary"/>
    <arg name="config_file_path" value="$(arg primary_config)"/>
    <arg name="trigger_out_enabled" value="true"/>
  </include>
</launch>

5.2.3.2. System Configuration Requirements

  1. Increase USB Buffer Memory

    Prevent frame drops caused by concurrent data transmission:

    echo 512 | sudo tee /sys/module/usbcore/parameters/usbfs_memory_mb

  2. Tune ROS1 Runtime Performance

    Optimize CPU and USB usage to reduce transmission delay and instability. See this section for detailed tuning instructions.