Triggering OAK using FSYNC issue

yishu_corpex

Hi,

I am triggering an OKA-D S2 PoE camera using FSYNC using an external trigger. As we know the color camera works on continuous mode only we need to mention a given FPS and also trigger the camera at the same FPS in order to get the RGB image as well.

I am able to get the RGB images but i see an issue with camera settings. For example, I am trying to use setManualExposure to fix the exposure value to a given value, however I feel as the camera gets triggered it sometimes resets the value to auto exposure. You get to see a blinking effect on each camera side. If i only use the RGB camera in continues mode using camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT) and make both the stereo camera's in snapshot mode by only using monoLeft.initialControl.setExternalTrigger(4,3) then i don't see the blinking effect in the stereo camera's but still see it in the RGB camera.

I have attached the screen recording of this issue below.

recording-2025-12-02-153039.mp4

49MB

Also I feel this issue is similar to this reported issues I think. Below is my updated code as well for your reference

import depthai as dai
import cv2
import time

pipeline = dai.Pipeline()

camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)
camRgb.setIspScale(2,3)
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.initialControl.setExternalTrigger(4,3)
camRgb.setFps(10)

xoutRgb = pipeline.create(dai.node.XLinkOut)
xoutRgb.setStreamName("color")
camRgb.isp.link(xoutRgb.input)

controlIn = pipeline.create(dai.node.XLinkIn)
controlIn.setStreamName('control')
controlIn.out.link(camRgb.inputControl)

monoLeft = pipeline.create(dai.node.MonoCamera)
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoLeft.setBoardSocket(dai.CameraBoardSocket.LEFT)
monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoLeft.initialControl.setExternalTrigger(4,3)

xoutLeft = pipeline.create(dai.node.XLinkOut)
xoutLeft.setStreamName("left")
monoLeft.out.link(xoutLeft.input)

monoRight = pipeline.createMonoCamera()
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setBoardSocket(dai.CameraBoardSocket.RIGHT)
monoRight.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoRight.initialControl.setExternalTrigger(4,3)

xoutRight = pipeline.create(dai.node.XLinkOut)
xoutRight.setStreamName("right")
monoRight.out.link(xoutRight.input)

i = 0 
# Connect to device with pipeline
device_info = dai.DeviceInfo("192.168.220.10")
with dai.Device(pipeline, device_info) as device:
    arr = ['left', 'right', 'color']
    queues = {}
    frames = {}
    controlQueue = device.getInputQueue('control')
    ctrl = dai.CameraControl()
    #ctrl.AutoFocusMode(dai.CameraControl.AutoFocusMode.AUTO)
    #ctrl.setAutoFocusRegion(100,1200,3500,700)
    #ctrl.setAutoExposureRegion(2028,0,2028,3040)
    #ctrl.setAutoFocusLensRange(100,125)

    #ctrl.setManualExposure(10000, 200) #1500, 700
    #ctrl.setContrast(8)
    
    ctrl.setManualExposure(15000, 200)   # 50 µs, gain 200
    ctrl.setManualFocus(158)

    #ctrl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
    #ctrl.setManualWhiteBalance(4000)
    controlQueue.send(ctrl)


    for name in arr:
        queues[name] = device.getOutputQueue(name)

    print("Starting...")

    while True:
        i += 1
        #print("No frames")
        for name in arr:
            if queues[name].has():
                #print("Image Available")
                img_frame = queues[name].get().getCvFrame()
                frames[name]= img_frame
                cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), img_frame)

        for name, frame in frames.items():
            cv2.imshow(name, frame)
            #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), frame)

        key = cv2.waitKey(1)
        if key == ord('q'):
            break

Thanks,
Yishu

OskarSonc

Hey @yishu_corpex - On OAK-D S2 the RGB sensor should stay in continuous mode – putting camRgbon setExternalTriggermakes it behave like a per-pulse snapshot and lets AE/AWB kick in, which causes the blinking. Try removing camRgb.initialControl.setExternalTrigger(4,3), keep only setFrameSyncMode(INPUT) with camRgb.setFps(10) to match your FSYNC rate, and in initialControl(and once via the control queue if you like) disable AE/AWB and set manual exposure. Keep the mono cameras in external trigger mode as you have.

Thanks,
Oskar

yishu_corpex

OskarSonc

I have already tried that as well. I made sure that the mono cameras are in snapshot mode and the RGB camera is in continuous mode. I also made sure the fps on the RGB is set to 10 FPS and the external trigger is also being sent at 10 FPS (to match the FSYNC rate). I set all my parameters like Exposure and witched off the AWB as well during the initial config. However, I still get the same issue on the RGB camera stream/images.

Below is my updated code for your reference.

#!/usr/bin/env python3
import depthai as dai
import cv2
import time

pipeline = dai.Pipeline()

camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)
camRgb.setIspScale(2,3)
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.initialControl.setManualExposure(4500, 200)
camRgb.initialControl.setManualFocus(142)
camRgb.initialControl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
#camRgb.initialControl.setExternalTrigger(4,3)
camRgb.setFps(10)

xoutRgb = pipeline.create(dai.node.XLinkOut)
xoutRgb.setStreamName("color")
camRgb.isp.link(xoutRgb.input)

controlIn = pipeline.create(dai.node.XLinkIn)
controlIn.setStreamName('control')
controlIn.out.link(camRgb.inputControl)

monoLeft = pipeline.create(dai.node.MonoCamera)
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoLeft.setBoardSocket(dai.CameraBoardSocket.LEFT)
#monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoLeft.initialControl.setExternalTrigger(4,3)
#monoLeft.setFps(10)

xoutLeft = pipeline.create(dai.node.XLinkOut)
xoutLeft.setStreamName("left")
monoLeft.out.link(xoutLeft.input)

monoRight = pipeline.createMonoCamera()
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setBoardSocket(dai.CameraBoardSocket.RIGHT)
#monoRight.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoRight.initialControl.setExternalTrigger(4,3)
#monoRight.setFps(10)

xoutRight = pipeline.create(dai.node.XLinkOut)
xoutRight.setStreamName("right")
monoRight.out.link(xoutRight.input)

i = 0 
# Connect to device with pipeline
device_info = dai.DeviceInfo("192.168.220.10")
with dai.Device(pipeline, device_info) as device:
    arr = ['left', 'right', 'color']
    queues = {}
    frames = {}
    controlQueue = device.getInputQueue('control')
    ctrl = dai.CameraControl()
    #ctrl.AutoFocusMode(dai.CameraControl.AutoFocusMode.AUTO)
    #ctrl.setAutoFocusRegion(100,1200,3500,700)
    #ctrl.setAutoExposureRegion(2028,0,2028,3040)
    #ctrl.setAutoFocusLensRange(100,125)

    #ctrl.setManualExposure(10000, 200) #1500, 700
    #ctrl.setContrast(8)
    
    ctrl.setManualExposure(4500, 200)   # 50 µs, gain 200
    ctrl.setManualFocus(142)

    ctrl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
    #ctrl.setManualWhiteBalance(4000)
    controlQueue.send(ctrl)


    for name in arr:
        queues[name] = device.getOutputQueue(name)

    print("Starting...")

    while True:
        i += 1
        #print("No frames")
        for name in arr:
            if queues[name].has():
                #print("Image Available")
                img_frame = queues[name].get().getCvFrame()
                frames[name]= img_frame
                #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), img_frame)

        for name, frame in frames.items():
            cv2.imshow(name, frame)
            #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), frame)

        key = cv2.waitKey(1)
        if key == ord('q'):
            break

Thanks,
Yishu

OskarSonc

Hmmm could yoou try something like this:

camRgb.setFps(10)
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.setWaitForConfigInput(True)  # don’t start streaming until we send control
camRgb.initialControl.setAutoExposureEnable(False)
camRgb.initialControl.setManualExposure(4500, 200)
camRgb.initialControl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
camRgb.initialControl.setManualFocus(142)

After creating the device, send the same control once before reading frames (this is what releases waitForConfigInput)

ctrl = dai.CameraControl()
ctrl.setAutoExposureEnable(False)
ctrl.setManualExposure(4500, 200)
ctrl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
ctrl.setManualFocus(142)
controlQueue = device.getInputQueue('control')
controlQueue.send(ctrl)

Leave mono cameras in snapshot mode with initialControl.setExternalTrigger(4,3) and also set frame-sync input to be explicit:

monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoRight.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)

Also do you have latest version of DepthAi v2 installed?

yishu_corpex

OskarSonc

camRgb.initialControl.setAutoExposureEnable(False)

This does not seem to be the right as it errors out (incompatible function arguments) and I think this function as per the documentation of depthai v2 can only be used to enable Auto Exposure mode and does not accept any arduments.

After creating the device, I send the same control once before reading frames and have commented the setAutoExposureEnable(False) as it errors out.

I have the mono cameras in snapshot mode. If I also set the frame-sync input to be explicit as mentioned by you above then I get the same blinking effect on the mono cameras as well as shown in the attached screen recording below.

recording-2025-12-10-103056.mp4

15MB

My updated code is below for your reference:

#!/usr/bin/env python3
import depthai as dai
import cv2
import time

pipeline = dai.Pipeline()

camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)
camRgb.setIspScale(2,3)
camRgb.setFps(10)
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.setWaitForConfigInput(True)  # don’t start streaming until we send control
#camRgb.initialControl.setAutoExposureEnable(False)
camRgb.initialControl.setManualExposure(4500, 200)
camRgb.initialControl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
camRgb.initialControl.setManualFocus(142)

xoutRgb = pipeline.create(dai.node.XLinkOut)
xoutRgb.setStreamName("color")
camRgb.isp.link(xoutRgb.input)

controlIn = pipeline.create(dai.node.XLinkIn)
controlIn.setStreamName('control')
controlIn.out.link(camRgb.inputControl)

monoLeft = pipeline.create(dai.node.MonoCamera)
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoLeft.setBoardSocket(dai.CameraBoardSocket.LEFT)
monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoLeft.initialControl.setExternalTrigger(4,3)
#monoLeft.setFps(10)

xoutLeft = pipeline.create(dai.node.XLinkOut)
xoutLeft.setStreamName("left")
monoLeft.out.link(xoutLeft.input)

monoRight = pipeline.createMonoCamera()
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setBoardSocket(dai.CameraBoardSocket.RIGHT)
monoRight.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoRight.initialControl.setExternalTrigger(4,3)
#monoRight.setFps(10)

xoutRight = pipeline.create(dai.node.XLinkOut)
xoutRight.setStreamName("right")
monoRight.out.link(xoutRight.input)

i = 0 
# Connect to device with pipeline
device_info = dai.DeviceInfo("192.168.220.10")
with dai.Device(pipeline, device_info) as device:
    arr = ['left', 'right', 'color']
    queues = {}
    frames = {}
    controlQueue = device.getInputQueue('control')
    ctrl = dai.CameraControl()
    #ctrl.setAutoExposureEnable(False)
    ctrl.setManualExposure(4500, 200)
    ctrl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
    ctrl.setManualFocus(142)
    controlQueue = device.getInputQueue('control')
    controlQueue.send(ctrl)


    for name in arr:
        queues[name] = device.getOutputQueue(name)

    print("Starting...")

    while True:
        i += 1
        #print("No frames")
        for name in arr:
            if queues[name].has():
                #print("Image Available")
                img_frame = queues[name].get().getCvFrame()
                frames[name]= img_frame
                #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), img_frame)

        for name, frame in frames.items():
            cv2.imshow(name, frame)
            #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), frame)

        key = cv2.waitKey(1)
        if key == ord('q'):
            break

Also, I have the latest DepthAI v2 version 2.31.0.0

Thanks,
Yishu

jakaskerl

yishu_corpex

#!/usr/bin/env python3
import depthai as dai
import cv2
import time

pipeline = dai.Pipeline()

camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)
camRgb.setIspScale(2,3)
camRgb.setFps(10)
camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
camRgb.setWaitForConfigInput(True)  # don’t start streaming until we send control
#camRgb.initialControl.setAutoExposureEnable(False)
camRgb.initialControl.setManualExposure(4500, 200)
camRgb.initialControl.setAutoWhiteBalanceMode(dai.CameraControl.AutoWhiteBalanceMode.OFF)
camRgb.initialControl.setManualFocus(142)

xoutRgb = pipeline.create(dai.node.XLinkOut)
xoutRgb.setStreamName("color")
camRgb.isp.link(xoutRgb.input)

controlIn = pipeline.create(dai.node.XLinkIn)
controlIn.setStreamName('control')
controlIn.out.link(camRgb.inputControl)

monoLeft = pipeline.create(dai.node.MonoCamera)
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoLeft.setBoardSocket(dai.CameraBoardSocket.LEFT)
monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoLeft.initialControl.setManualExposure(4500, 200)
monoLeft.initialControl.setExternalTrigger(1,1)
#monoLeft.setFps(10)

xoutLeft = pipeline.create(dai.node.XLinkOut)
xoutLeft.setStreamName("left")
monoLeft.out.link(xoutLeft.input)

monoRight = pipeline.createMonoCamera()
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setBoardSocket(dai.CameraBoardSocket.RIGHT)
monoRight.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
monoRight.initialControl.setExternalTrigger(1,1)
monoRight.initialControl.setManualExposure(4500, 200)
#monoRight.setFps(10)

xoutRight = pipeline.create(dai.node.XLinkOut)
xoutRight.setStreamName("right")
monoRight.out.link(xoutRight.input)

i = 0 
# Connect to device with pipeline
device_info = dai.DeviceInfo("192.168.220.10")
with dai.Device(pipeline) as device:
    arr = ['left', 'right', 'color']
    queues = {}
    frames = {}
    controlQueue = device.getInputQueue('control')
    ctrl = dai.CameraControl()
    #ctrl.setAutoExposureEnable(False)
    ctrl.setManualExposure(4500, 200)
    ctrl.setManualFocus(142)
    controlQueue = device.getInputQueue('control')
    controlQueue.send(ctrl)


    for name in arr:
        queues[name] = device.getOutputQueue(name)

    print("Starting...")

    while True:
        i += 1
        #print("No frames")
        for name in arr:
            if queues[name].has():
                #print("Image Available")
                img_frame = queues[name].get().getCvFrame()
                frames[name]= img_frame
                #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), img_frame)

        for name, frame in frames.items():
            cv2.imshow(name, frame)
            #cv2.imwrite("C:/EMVS_Development_Camera_Scripts/OAK_IO_Triggering/images/"+str(name)+"_Image{}.bmp".format(i), frame)

        key = cv2.waitKey(1)
        if key == ord('q'):
            break