How to capture photos in a fixed frequency while flying?

[Konjak2e8]

I tried using multithread to make a drone capture photos while flying by trajectory. However, after it reached the first trajectory point, the drone just hovered there, and the python script keeps waiting for simGetImages() to complete. Here is my code:

import threading
import time
import airsim
import numpy as np
import os
import tempfile
import cv2
import pandas as pd

# params
num_drone = 1  # drone index
fixed_height = -15  
trajectory_file = './trace/u_xy/u_xy1.csv'
photo_interval = 0.1  # in second

# read trajectories
all_drones_df = pd.read_csv(trajectory_file, header=0)
drone_trajectory = all_drones_df.iloc[num_drone-1::10].values / 10

# connect to AirSim
client = airsim.MultirotorClient()
client.confirmConnection()

# init drones
client.enableApiControl(True, vehicle_name=f"UAV{num_drone}")
client.armDisarm(True, vehicle_name=f"UAV{num_drone}")
client.takeoffAsync(vehicle_name=f"UAV{num_drone}").join()
client.moveToZAsync(fixed_height, 5, vehicle_name=f"UAV{num_drone}").join()

def capture_photos():
    while not stop_thread:
        # take photos and save as image
        responses = client.simGetImages([
            airsim.ImageRequest("front_center", airsim.ImageType.DepthVis),
            airsim.ImageRequest("front_center", airsim.ImageType.Scene, False, False)
        ], vehicle_name=f"UAV{num_drone}")
        
        tmp_dir = os.path.join(tempfile.gettempdir(), f"airsim_drone{num_drone}")
        os.makedirs(tmp_dir, exist_ok=True)
        step_time = int(time.time())  # name photos by timestamp

        for idx, response in enumerate(responses):
            filename = os.path.join(tmp_dir, f"{step_time}_{idx}.png")
            if response.compress:  # check if the photos are compressed
                with open(filename, 'wb') as f:
                    f.write(response.image_data_uint8)
            else:  # if not compressed
                img1d = np.frombuffer(response.image_data_uint8, dtype=np.uint8)
                img_rgb = img1d.reshape(response.height, response.width, 3)
                cv2.imwrite(filename, img_rgb)
        time.sleep(photo_interval)

# start taking photos
stop_thread = False
photo_thread = threading.Thread(target=capture_photos)
photo_thread.start()

# fly by trajectory
for (x, y) in drone_trajectory:
    client.moveToPositionAsync(x, y, fixed_height, 6, vehicle_name=f"UAV{num_drone}").join()

# stop taking photos
stop_thread = True
photo_thread.join()

# land
client.landAsync(vehicle_name=f"UAV{num_drone}").join()
client.armDisarm(False, vehicle_name=f"UAV{num_drone}")
client.enableApiControl(False, vehicle_name=f"UAV{num_drone}")

settings.json is here:

{
  "SeeDocsAt": "https://github.com/Microsoft/AirSim/blob/main/docs/settings.md",
  "SettingsVersion": 1.2,
  "SimMode": "Multirotor",
  "ViewMode": "Manual",
  "ClockSpeed": 1,
  "SubWindows": [
    {"WindowID": 0, "ImageType": 0, "CameraName": "front_center", "Visible": true},
    {"WindowID": 1, "ImageType": 3, "CameraName": "front_center", "Visible": true},
    {"WindowID": 2, "ImageType": 4, "CameraName": "front_center", "Visible": true}
  ],
  "Recording": {
    "RecordInterval": 0.05,
    "Cameras": [
        { "CameraName": "front_center", "ImageType": 0, "PixelsAsFloat": false, "Compress": true }
    ]
  },
  "CameraDefaults": {
    "CaptureSettings": [
      {
        "ImageType": 0,
        "Width": 600,
        "Height": 400,
        "FOV_Degrees": 90
      }
    ]
  },
  "Vehicles": {
    "UAV1": {
      "VehicleType": "SimpleFlight",
      "X": 0, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV2": {
      "VehicleType": "SimpleFlight",
      "X": 1.5, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV3": {
      "VehicleType": "SimpleFlight",
      "X": -1.5, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV4": {
      "VehicleType": "SimpleFlight",
      "X": 3, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV5": {
      "VehicleType": "SimpleFlight",
      "X": -3, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV6": {
      "VehicleType": "SimpleFlight",
      "X": 4.5, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV7": {
      "VehicleType": "SimpleFlight",
      "X": -4.5, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV8": {
      "VehicleType": "SimpleFlight",
      "X": 6, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV9": {
      "VehicleType": "SimpleFlight",
      "X": -6, "Y": 0, "Z": 0,
      "Yaw": 0
    },
    "UAV10": {
      "VehicleType": "SimpleFlight",
      "X": 7.5, "Y": 0, "Z": 0,
      "Yaw": 0
    }
  }
}