Reset Camera Timestamp in Python

[kranok-dev]

Hi,

I would like to know how to reset the camera's timestamp in Python? Can't seem to find the equivalent of GevTimestampControlReset to Python from the documentation.

Thank you,

[Abhilashsabhi]

@kranok-dev Got Any solution?

[thiesmoeller]

https://docs.baslerweb.com/timestamp#resetting-the-timestamp-value

[SMA2016a]

This parameter is only available on a GigE camera. Do you have GigE or USB camera?

[kranok-dev]

@Abhilashsabhi, not yet :(

@SMA2016a, it's USB camera. Is it possible to reset the timestamp from a USB camera without being powered off? If the camera is on for extended period of time without being reset, would the timestamp variable overflow?

[thiesmoeller]

@kranok-dev .. you saw the docu link ?

And one other advice. Typically you track this in the application. E.g. by matching it to system clock with a running mean or even a proper fitting over the last e.g. minute.( Cam time vs precision system time directly after RetrieveResult) This way you can assign precision system time to each frame received

[kranok-dev]

@thiesmoeller, yes, thank you for sharing. Though the reset command (GevTimestampControlReset) doesn't seem to work for me in Python. Do you know what the equivalent function is in Python?

Right now, I'm matching system time with the camera's tick count before capture. After capture, I get the timestamp from the grab_result object, subtract the camera's tick count before capture, and add the corresponding seconds (adjusting the camera ticks to seconds) to the system time I got before capture.

[thiesmoeller]

The Docs are dynamic. Please select your camera in the top menu

As the userland timestamp jitters a lot you habe to average or even do a fit over multiple frames to vet the precise time

[kranok-dev]

Yes, I have put one of the cameras I'm using but I'm not sure how to call such function (TimestampReset) with Python:

From the camera object, I only find these functions:

• ...
• TestPendingAck
• TimerControl
• TimerDelay
• TimerDuration
• TimerReset
• TimerSelector
• TimerStatus
• TimerTriggerActivation
• TimerTriggerArmDelay
• TimerTriggerSource
• TimestampLatch
• TimestampLatchValue
• TransportLayer
• TransportLayerControl
• TriggerActivation
• TriggerDelay
• TriggerEventTest
• TriggerMode
• TriggerSelector
• TriggerSoftware
• TriggerSource
• ...

[thiesmoeller]

@kranok-dev :-/ it might be that your cameras don't have the function Timestamp reset

Nevertheless the timestamp is a 64bit counter at 1GHz.
Due to the fact that genicam only has signed int64 datatypes, 63 bits are usable.

This results in a usable time of >292 years. This should be enough for most applications.

[kranok-dev]

@thiesmoeller understood, I appreciate the follow-up and clarification, thank you.

[Abhilashsabhi]

I have Basler acA1920-40 gc cameras, which are directly connected to my system. Then I synchronized cameras using GNSS. Now GNSS is acting as the grandmaster, and my system is acting as the boundary clock, and the cameras are slaves. I enabled all cameras' synchronous free run option in the Pylon Viewer and set the frame rate to 10. Then I wrote the following code for recording images from all the cameras. Can anyone verify if the code is correct?

#!/usr/bin/env python3
# Basler multi-camera PTP + ROS publishing (2x3 grid + individual cameras)

from pypylon import pylon
import time
import rospy
import cv2
import numpy as np
from sensor_msgs.msg import Image
from std_msgs.msg import Header
from cv_bridge import CvBridge

TARGET_SERIALS = ["24264461","24264465","24264462","24264477","24222613","24135744"]
PTP_WAIT_TIMEOUT_S = 60
GRID_TOPIC = "/camera_grid/image_raw"

bridge = CvBridge()


def wait_until_ptp_slave(cam, timeout_s=PTP_WAIT_TIMEOUT_S):
    start = time.time()
    status_node = getattr(cam, "GevIEEE1588Status", None)
    offset_node = getattr(cam, "GevIEEE1588OffsetFromMaster", None)
    last_report = ""
    while time.time() - start < timeout_s:
        try:
            state = status_node.GetValue() if status_node else ""
        except Exception:
            state = ""
        if state == "Slave":
            try:
                off = offset_node.GetValue() if offset_node else None
                print(f"[{cam.DeviceSerialNumber.GetValue()}] PTP state=Slave, OffsetFromMaster={off} ns")
            except Exception:
                print(f"[{cam.DeviceSerialNumber.GetValue()}] PTP state=Slave")
            return True
        if state and state != last_report:
            print(f"[{cam.DeviceSerialNumber.GetValue()}] PTP state={state} (waiting for Slave)")
            last_report = state
        time.sleep(0.2)
    print(f"[{cam.DeviceSerialNumber.GetValue()}] WARNING: Timed out waiting for PTP Slave (last state: {last_report})")
    return False


def configure_ptp_freerun(cam):
    cam.Open()
    if hasattr(cam, "GevIEEE1588"):
        cam.GevIEEE1588.SetValue(True)
        print(f"[{cam.DeviceSerialNumber.GetValue()}] PTP enabled")
    else:
        raise RuntimeError("Camera does not expose GevIEEE1588 parameter (PTP not supported?).")
    cam.TriggerSelector.SetValue("FrameStart")
    cam.TriggerMode.SetValue("Off")
    cam.Close()


def find_cameras(serials=None):
    tl_factory = pylon.TlFactory.GetInstance()
    devices = tl_factory.EnumerateDevices()
    if not devices:
        raise RuntimeError("No Basler cameras found.")
    if serials:
        by_sn = {d.GetSerialNumber(): d for d in devices}
        selected = []
        for sn in serials:
            if sn not in by_sn:
                raise RuntimeError(f"Requested camera with serial {sn} not found.")
            selected.append(by_sn[sn])
        return selected
    return devices


def main():
    rospy.init_node("basler_multicam_node")
    devices = find_cameras(TARGET_SERIALS)
    print(f"Discovered {len(devices)} camera(s).")

    cameras = [pylon.InstantCamera(pylon.TlFactory.GetInstance().CreateDevice(d)) for d in devices]

    # Publishers
    pub_grid = rospy.Publisher(GRID_TOPIC, Image, queue_size=1)
    pub_individual = [rospy.Publisher(f"/camera_{cam.GetDeviceInfo().GetSerialNumber()}/image_raw", Image, queue_size=1)
                      for cam in cameras]

    # Pylon converter
    converter = pylon.ImageFormatConverter()
    converter.OutputPixelFormat = pylon.PixelType_RGB8packed
    converter.OutputBitAlignment = pylon.OutputBitAlignment_MsbAligned

    # Configure cameras
    for cam in cameras:
        sn = cam.DeviceSerialNumber.GetValue() if cam.IsOpen() else "[unknown SN]"
        print(f"Configuring camera {sn}...")
        configure_ptp_freerun(cam)

    # Wait for PTP sync
    print("Waiting for all cameras to become PTP Slave...")
    all_ok = True
    for cam in cameras:
        cam.Open()
        ok = wait_until_ptp_slave(cam, timeout_s=PTP_WAIT_TIMEOUT_S)
        cam.Close()
        all_ok = all_ok and ok

    if not all_ok:
        print("WARNING: Not all cameras reached PTP Slave. Timestamps may not be aligned.")

    # Start grabbing
    for cam in cameras:
        cam.Open()
        cam.StartGrabbing(pylon.GrabStrategy_LatestImageOnly)
    rate = rospy.Rate(30)
    try:
        while not rospy.is_shutdown():
            imgs = []
            timestamps = []

            for i, cam in enumerate(cameras):
                if cam.IsGrabbing():
                    res = cam.RetrieveResult(500, pylon.TimeoutHandling_Return)
                    if res and res.GrabSucceeded():
                        img_rgb = converter.Convert(res).Array
                        imgs.append(img_rgb)
                        timestamps.append(res.TimeStamp)

                        # Publish individual camera
                        ts_ns = res.TimeStamp
                        sec = ts_ns // 1_000_000_000
                        nsec = ts_ns % 1_000_000_000
                        header = Header()
                        header.stamp = rospy.Time(sec, nsec)
                        header.frame_id = f"camera_{cam.DeviceSerialNumber.GetValue()}_frame"
                        msg = bridge.cv2_to_imgmsg(img_rgb, encoding="rgb8")
                        msg.header = header
                        pub_individual[i].publish(msg)

                        res.Release()

            rate.sleep()
    finally:
        for cam in cameras:
            if cam.IsGrabbing():
                cam.StopGrabbing()
            cam.Close()
        print("Exiting.")


if __name__ == "__main__":
    main()

[Abhilashsabhi]

Please review the attached code and let me know if any issues are there in the code.