Hardware trigger synchronization including RGB image (Oakd-s2)

toon

I am trying to trigger my Oakd-s2 (AF) on ubuntu24 with the example provided here.

https://gist.github.com/Erol444/0138af63378dc8de5b3f7d80db1ea1a5

I managed to get this script working, however, the RGB image is not shown. In the following thread, https://discuss.luxonis.com/d/2304-multiple-oak-ffc-4p-based-cameras-timestamp-sync/5 it was said that they got the trigger working included RGB image, unfortunately any example is missing. Could this be shared?

jakaskerl

toon
You are using an external trigger right?

The code is meant for OAK-FFC (or POE M8) devices where the FSIN is exposed. This is not possible on S2 unless you open it and connect it to a FSIN line (which is not easily accessible).

Thanks,
Jaka

erik

@toon RGB camera won't work because the sensor doesn't support "snapshot" triggering, only "continuous" triggering at a very fixed intervals (eg. 30.00Hz). Pleas see link below for details:
https://docs.luxonis.com/hardware/platform/deploy/frame-sync/#Sensor%20FSYNC%20support
Thanks, Erik

toon

jakaskerl sorry for the misconfusion, I am using a OAK-D S2 PoE with autofocus, so I have already implemented the M8 connector.

What I would like to do is to trigger multiple devices (3) with a external trigger pulse. Furthermore I want to output an rgb image as close as possible with the triggered mono-images, but they don't have to be fully hardware synchronised.

jakaskerl

toon
Then the code is fine, just set the color camera FPS to the exactly the same FPS at which you are triggering the other two cameras. As Erik said, snapshot mode does not work.

Continuous streaming with external syncing, configured with CameraControl.setFrameSyncMode(). In this mode, the FSIN signal is expected to arrive at a continuous rate matching the configured sensor FPS, and trigger can't arrive at arbitrary times as that would disrupt internal sensor operations (leading to bad frames, etc). It can only correct for very small amounts of drift over time.

Thanks,
Jaka

jakaskerl

toon
You need to trigger at exactly 30Hz for this to work. as mentioned in jakaskerl

toon

Dear Jakaskerl,

Indeed the color camera in following script does not work example.

Instead I wrote the following script including sync node, but still I do not get an image, what am I doing wrong?

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

# FPS_tof = 10
FPS_rgb = 10
with_trigger = True


pipeline = dai.Pipeline()

# RGB camera
camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)
camRgb.setIspScale(2, 3)
camRgb.setBoardSocket(dai.CameraBoardSocket.RGB)
camRgb.setFps(FPS_rgb)
if with_trigger:
    camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
    camRgb.initialControl.setExternalTrigger(4, 3)


xout = pipeline.create(dai.node.XLinkOut)
xout.setStreamName("out")
# camRgb.isp.link(xout.input)  # Link the RGB output to XLinkOut

# Mono left camera
monoLeft = pipeline.create(dai.node.MonoCamera)
monoLeft.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoLeft.setBoardSocket(dai.CameraBoardSocket.LEFT)
monoLeft.setFps(FPS_rgb)
if with_trigger:
    monoLeft.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)
    monoLeft.initialControl.setExternalTrigger(4, 3)

# Mono right camera
monoRight = pipeline.create(dai.node.MonoCamera)
monoRight.setResolution(dai.MonoCameraProperties.SensorResolution.THE_720_P)
monoRight.setBoardSocket(dai.CameraBoardSocket.RIGHT)
monoRight.setFps(FPS_rgb)
if with_trigger:
    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)

# Sync node (if you want to sync all cameras)
sync = pipeline.create(dai.node.Sync)
# sync.setSyncThreshold(50)  # Sync threshold in milliseconds
sync.setSyncThreshold(timedelta(milliseconds=1000))

# Linking RGB, left, and right to the sync node
camRgb.isp.link(sync.inputs["color"])  # Link RGB to sync
monoLeft.out.link(sync.inputs["left"])
monoRight.out.link(sync.inputs["right"])

# You can link the sync output to XLinkOut for all cameras
sync.out.link(xout.input)
# sync.out.link(xoutLeft.input)
# sync.out.link(xoutRight.input)

# Device connection
device_id = "169.254.1.103"
with dai.Device(pipeline, dai.DeviceInfo(device_id)) as device:

    queue = device.getOutputQueue("out", 8, False)
    queueright=device.getOutputQueue("right")

    print("Starting...", queue)
    while True:
        # if queueright["right"].has():
        #     test=queueright["right"].get().getCvFrame()
        #     print("x")
        messageGroup: dai.MessageGroup = queue.get()
        frameMono_right: dai.ImgFrame = messageGroup["right"]
        frameMono_left: dai.ImgFrame = messageGroup["left"]
        # frameDepth_tof: dai.ImgFrame = messageGroup["depth_tof"]
        frameRgb: dai.ImgFrame = messageGroup["color"]
        # Blend when both received
        if frameMono_right is not None:
            if frameRgb is not None:
                print(frameMono_right.getSequenceNum())
                print(frameRgb.getSequenceNum())
                # print(messageGroup["depth"].getTimestamp()-messageGroup["rgb"].getTimestamp())
                # print(messageGroup["rgb"].getSequenceNum())
                # print(messageGroup["depth"].getSequenceNum())
                monoRight_img = frameMono_right.getCvFrame()
                # # cv2.imshow("rgb", frameRgb)
                # # cv2.imshow("depth", colorizeDepth(frameDepth.getCvFrame()))
                test=frameRgb.getCvFrame()
                print("It is working")
            else:
                print("no depth frame")
        else:
            print("no rgb frame")

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


cv2.destroyAllWindows()

jakaskerl

toon
How does the trigger signal look?

Thanks,
Jaka

toon

The trigger signal is just a signal triggered by a pushbutton (for test and verification). Same setup as in externally trigger fsync. In the end we would like to trigger with a PLC based on the encoder value (every x cm).

toon

Ok, so if I understand correctly, there is no way to hardware-trigger the stereo frames and then find the most close rgb-frame softwarematticaly (even if we leave it streaming at 30FPS)?

jakaskerl

toon
Correct, the frame triggers are expected (by IMX378) to come at a fixed rate. The issue is the the fsin lines are connected together and only triggering the OV strereo cameras wouldn't work. If the lines were separate this should be possible.

RGB will not stream if both left and right are set to input mode.

Thanks,
Jaka

toon

Dear @jakaskerl

We have tested the provided code with an configured external trigger on 6hz. The left and rgb camera are streaming. However after ±1 minutes a fraction of the color images is under-exposed. It looks like that the fraction of the image, has an older frame? Could you help me out. I am using the following example script:

https://docs.luxonis.com/hardware/platform/deploy/frame-sync/#Sensor%20FSYNC%20support

Thanks in advance.

jakaskerl

toon
Can you share some minimal reproducible code?

Thanks,
Jaka

toon

If I copy paste the code, somehow identation is incorrect, so a link instead:

https://filesender.surf.nl/?s=download&token=52d56732-0b4d-445d-afae-3868a4c9d5f2

Code is similar as the example, except for line 14 (set FPS for the RGB camera). Trigger signal is 6hz.

jakaskerl

toon
I'll check tomorrow. But it looks like there is some drift... Does the image get better if you wait some time - so it gets in sync?

Thanks,
Jaka

toon

First minute it works, then in steps of 5 you will see more and more part of the image becoming darker, until you get something like the image above. How accurate does the trigger need to be? I am currently using a revolution pi to create the signal which I believe is accurate, however of course it can be a few microseconds off.

toon

Update if add manual exposure:

camRgb.initialControl.setManualExposure(1000,300) # exposturetime US, sensitivityIs

Then output is consistent incorrect:

Also it seems that sometimes a trigger is missed. Even at low fps of 6, I am missing a few frames. Both infrared and colour camera. What should be the duration of the trigger?

jakaskerl

toon
cc @Luxonis-Alex any ideas to what might be happening?

Thanks,
Jaka

bartvm

Hi @jakaskerl , Bart a colleague of Toon here.

We did some additional experiments today, and the issue appears when setting the exposure time < 17000 us. I am going to use my camera in high light conditions, so this is not acceptable for me.

Second observation is even with fixed exposure the video stream is changing a lot. See example video below with in the terminal the exposure. This is caused by the line:

camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT) # should be enabled otherwise it is streaming continuous

If i disable the setFrameSynMode "flashing" does not occur.

another qustion is the SetFrameSynMode also required for left and right camera? If I do that streaming of infrared images does not work.

To summarize:

How to trigger RGB and Infrared camera below 17000 us?
How to prevent "flashing" issue (occurs as well without fixed exposure)?
The SetFrameSyncMode, should it be enabled for infrared left and right as well?

luxonis-recording-17000us.mp4

3MB

#!/usr/bin/env python3

import depthai as dai

import cv2

import time

fps = 15focus = 126
expTime = 17000 # if <10000 black images will appear
sensIso = 100
pipeline = dai.Pipeline()
camRgb = pipeline.create(dai.node.ColorCamera)
camRgb.setColorOrder(dai.ColorCameraProperties.ColorOrder.RGB)camRgb.initialControl.setManualFocus(focus)camRgb.initialControl.setManualExposure(expTime,sensIso) # exposturetime US, sensitivityIsocamRgb.setFps(fps)
camRgb.setIspScale(2,3)camRgb.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT) # should be enabled otherwise it is streaming continuous
xoutRgb = pipeline.create(dai.node.XLinkOut)xoutRgb.setStreamName("color")camRgb.isp.link(xoutRgb.input)
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) ## if I enable this at some point it will freezemonoLeft.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) ## if i enable this at some point int will freezemonoRight.initialControl.setExternalTrigger(4,3)# monoRight.setFps(fps)
xoutRight = pipeline.create(dai.node.XLinkOut)xoutRight.setStreamName("right")monoRight.out.link(xoutRight.input)
# Connect to device with pipeline# with dai.Device(pipeline) as device: # Device connectiondevice_id = "169.254.1.114"with dai.Device(pipeline, dai.DeviceInfo(device_id)) as device: # controlQueue = device.getInputQueue('control') # ctrl = dai.CameraControl() # ctrl.setManualExposure(expTime, sensIso) # controlQueue.send(ctrl)
arr = ['left', 'right','color'] queues = {} frames = {}
for name in arr: queues[name] = device.getOutputQueue(name)
print("Starting...") counter = 0 msg_exp = None while True: for name in arr: if queues[name].has(): msg = queues[name].get() frames[name]=msg.getCvFrame() if name=="color": msg_exp = msg
for name, frame in frames.items(): cv2.imshow(name, frame) counter +=1
if msg_exp is not None: print("exposure rgb [us] %d"%(msg_exp.getExposureTime().total_seconds()*1e6))

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

bartvm

Forgot to mention the shorter the the exposure time, the more the line shifts upwards. Flashing only occurs at bright part. For example 10000us:

5000us