# Multi camera sync



<!-- TOC -->

- Contents:

  - [Preparation](#preparation)
  - [Check the camera usb port](#check-the-camera-usb-port)
  - [Configure multi_camera_synced.launch.py](#configure-multi_camera_synced.launch.py)
  - [Run multi_camera_synced.launch.py](#run-multi_camera_synced.launch.py)
  - [Advanced Parameters](#advanced-parameters)
  - [Gmsl example](#gmsl-example)
<!-- TOC -->

----------------------------------------------------------------



## Preparation

First, please read the Multi-machine Synchronizer User Documentation:[https://www.orbbec.com/docs/set-up-cameras-for-external-synchronization_v1-2/](https://www.orbbec.com/docs/set-up-cameras-for-external-synchronization_v1-2/)

Secondly,make sure the camera is properly connected to the multi-camera synchronizer

Finally,please browse the launch file for multi-machine synchronous startup:[https://github.com/orbbec/OrbbecSDK_ROS2/blob/main/orbbec_camera/launch/multi_camera_synced.launch.py](https://github.com/orbbec/OrbbecSDK_ROS2/blob/main/orbbec_camera/launch/multi_camera_synced.launch.py)

## Check the camera usb port

```bash
ros2 run orbbec_camera list_devices_node
```

Output:

![Multi_camera1](../image/Multi_camera1.png)

## Configure multi_camera_synced.launch.py

Open multi_camera_synced.launch.py, the camera configuration is as shown below

![Multi_camera1](../image/Multi_camera2.png)

1.gemini_330_series.launch.py is the camera startup file

2.camera_name is set to front_camera, for example, the color image topic name is /front_camera/color/image_raw"

3.**usb_port is set to 2-7, indicating that the 2-7 camera device is started**, 2-7 is taken from the usb port output by ros2 run orbbec_camera list_devices_node

4.device_num is set to 4, indicating that four cameras are started

5.**sync_mode is set to software_triggering**, indicating that the 2-7 camera device is set to software trigger mode, and the selection of multi-machine synchronization mode can refer to the following figure

6.Calling the parameter settings in config_file_path will overwrite the parameter settings in emini_330_series.launch.py, optional

![Multi_camera1](../image/Multi_camera3.png)

multi_camera_synced.launch.py camera startup order, the host must be started last

![Multi_camera1](../image/Multi_camera4.png)

## Run multi_camera_synced.launch.py

```bash
ros2 launch orbbec_camera multi_camera_synced.launch.py
```

## Advanced Parameters

Some camera parameters are related to multi-camera sync

| Camera parameters       | action                                                        |
| ----------------------- | ------------------------------------------------------------- |
| trigger_out_enabled     | Trigger signal switch setting                                 |
| trigger2image_delay_us  | Configure the secondarydepth delay and secondarycolor delay  |
| trigger_out_delay_us    | Trigger signal delay                                          |
| frames_per_trigger      | Software trigger frequency(used with software_trigger_period) |
| software_trigger_period | Software trigger interval(used with frames_per_trigger)       |

## Gmsl example

![Multi_camera1](../image/gmsl_1.png)