| Product | Support sync mode | Notes |
|---|---|---|
| Astra 2 | Primary, Secondary-synced | The Sync mode settings are retained after power cycling |
- USB devices must be connected to a sync hub (via the 8-pin port). Please refer to the Multi-device Sync documentation.
The standard hardware cable sync mode. One device acts as the Primary outputting sync trigger signals, while the other devices act as Secondary receiving trigger signals, achieving frame exposure synchronization across all devices.
Use case: Multi-device synchronized capture via USB connection, using the standard 8-pin sync cable + sync hub solution.
How it works:
- The Primary device sends a hardware trigger signal via the 8-pin sync cable at each frame exposure.
- The sync hub distributes the signal to secondary devices.
- Secondary devices perform exposure capture upon receiving the trigger signal.
Startup sequence:
- Start all Secondary devices first (wait for initialization to complete).
- Start the Primary device last.
| Field | Description |
|---|---|
syncMode |
Sync mode. Available values: OB_MULTI_DEVICE_SYNC_MODE_PRIMARY, OB_MULTI_DEVICE_SYNC_MODE_SECONDARY_SYNCED |
depthDelayUs |
Configure depth trigger delay, unit: microseconds |
colorDelayUs |
Color trigger signal input delay in microseconds. |
trigger2ImageDelayUs |
Delay from trigger signal input to image capture in microseconds. |
triggerOutEnable |
Device trigger signal output enable switch |
triggerOutDelayUs |
Device trigger signal output delay in microseconds. |
framesPerTrigger |
Number of frames captured per trigger. Only effective in SOFTWARE_TRIGGERING and HARDWARE_TRIGGERING modes, typically set to 1 |
- The MultiDeviceSyncConfig.json configuration for the Astra 2 device differs between Star Topology and Daisy-chain Topology. Please update the file according to the actual topology being used.
The Star Topology configuration file is as follows:
- triggerOutDelayUs: -1 represents the default exposure output time for the camera; 0 indicates that no external trigger signal is being sent.
- trigger2ImageDelayUs: To avoid laser interference between multiple cameras, e.g., device 1 = 0, device 2 = 4000us, device 3 = 8000us ...
{
"sn": "CP2194200060",
"syncConfig": {
"syncMode": "OB_MULTI_DEVICE_SYNC_MODE_PRIMARY",
"depthDelayUs": 0,
"colorDelayUs": 0,
"trigger2ImageDelayUs": 0,
"triggerOutEnable": true,
"triggerOutDelayUs": -1,
"framesPerTrigger": 1
}
}{
"sn": "CP0Y8420004K",
"syncConfig": {
"syncMode": "OB_MULTI_DEVICE_SYNC_MODE_SECONDARY_SYNCED",
"depthDelayUs": 0,
"colorDelayUs": 0,
"trigger2ImageDelayUs": 4000,
"triggerOutEnable": true,
"triggerOutDelayUs": 0,
"framesPerTrigger": 1
}
}The Daisy-chain Topology configuration file is as follows:
- triggerOutDelayUs: -1 represents the default exposure output time for the camera; 0 indicates that no external trigger signal is being sent.
{
"sn": "CP2194200060",
"syncConfig": {
"syncMode": "OB_MULTI_DEVICE_SYNC_MODE_PRIMARY",
"depthDelayUs": 0,
"colorDelayUs": 0,
"trigger2ImageDelayUs": 0,
"triggerOutEnable": true,
"triggerOutDelayUs": -1,
"framesPerTrigger": 1
}
}{
"sn": "CP0Y8420004K",
"syncConfig": {
"syncMode": "OB_MULTI_DEVICE_SYNC_MODE_SECONDARY_SYNCED",
"depthDelayUs": 0,
"colorDelayUs": 0,
"trigger2ImageDelayUs": 0,
"triggerOutEnable": true,
"triggerOutDelayUs": -1,
"framesPerTrigger": 1
}
}Open a terminal and navigate to the project directory:
cd Multi-Device-Synchronization-Example
mkdir build
cd build
cmake ..
cmake --build . --config ReleaseEdit the configuration file to match your actual device serial numbers. Device serial numbers can be viewed using the OrbbecViewer tool or found in the program log after connecting the devices.
The following demonstrates how to use the multi-device synchronization sample on Windows.
- Double-click MultiDeviceSync.exe. When the following dialog appears, select 0.
0: Configure sync mode and start stream
1: Start stream: If the parameters for multi-device sync mode have been configured, you can start the stream directly.
- Multi-device synchronization test results are as follows
Observe the timestamps. As shown in the figure below, the device timestamps of the two devices are identical, indicating that the two devices are successfully synchronized.
- For USB device or Ethernet device multi-device synchronization, simply execute MultiDeviceSync.
$ ./MultiDeviceSync
-
After starting the device, press 'ESC' in the image preview window to stop the data stream and exit the program. Abnormal program termination may cause incomplete shutdown of the device, leading to continuous triggering of the secondary device (restarting the device can resolve this).
-
The same device can only be accessed by one application at a time. Opening the same device with multiple applications simultaneously may cause anomalies. Please use with caution.
-
Using AE (Auto Exposure) may result in synchronization delays due to significant environmental differences between cameras. It is recommended to use the SDK to call exposure control interfaces and set fixed exposures to mitigate this issue.
-
For Linux computers, such as Ubuntu, the default kernel allocates only 16 MB of memory for USB controllers to handle USB transfers. This amount may be insufficient for high-resolution images or multiple streams and devices. To support multiple devices, the USB controller must have more memory allocated. Follow these steps to increase the allocated memory:
echo 128 | sudo tee /sys/module/usbcore/parameters/usbfs_memory_mb
To make this change permanent:
Open the /etc/default/grub file, find and replace:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
with this
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash usbcore.usbfs_memory_mb=128"
Update grub
sudo update-grub
Reboot and check
cat /sys/module/usbcore/parameters/usbfs_memory_mb