在Python OpenCV2中多个摄像机之间小于1帧的切换

Question

有人对如何快速切换由python开放CV2程序控制的网络摄像机阵列有更好的想法吗?我希望在切换相机之间没有明显的停顿。我愿意学习其他语言，比如c++ ?

目前为止我有什么:

#%% import the opencv library
import cv2
from multiprocessing import Queue, Process, Manager
import time
import keyboard
import glob
import threading
import signal
import sys
#%%
baseVidList = glob.glob("/dev/video*")
baseVidList = baseVidList[:-2]
#%%
manager = Manager()
selectedCam = manager.Value('i', 0)
endSignal = manager.Value('i', 0)
qqq = Queue()
vidDict = {}

# define a video capture object
for device in baseVidList:
vidDict[device] = lambda: cv2.VideoCapture(f"{device}")
#%%
ejections = []
for device, capDevice in vidDict.items():
vidDict[device] = capDevice()
if vidDict[device].isOpened():
print(f"{device} Sucess")
vidDict[device].set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'))
else:
print(f"{device} Failed, Ejecting")
vidDict[device].release()
ejections.append(device)
for eject in ejections:
vidDict.pop(eject)
#%%
font = cv2.FONT_HERSHEY_SIMPLEX
#### Functions ####
# Thread class
class VideoCaptureThread(threading.Thread):
def __init__(self, device, camID, endSignal):
super().__init__()
self.camID = camID
self.device = device
self.stopped = False
self.fps = 10
self.endSignal = endSignal
def run(self):
print("RUNNNN", self.endSignal != 1)
while self.endSignal != 1:
start_time = time.time()
print("S cam is:", selectedCam.value)
ret, frame = self.device.read()
if ret and selectedCam.value == self.camID:
# print(self.camID, xW, yH)
cv2.putText(frame,f"{self.camID}",(100,100),font,1,(255,0,0),1)
qqq.put(frame)
# Control the frame rate
sleep_time = 1/self.fps - (time.time() - start_time)
if sleep_time > 0:
time.sleep(sleep_time)
def stop(self):
self.stopped = True
self.device.release()
# Multiprocessing thread launch
def runCamera(device, camID):
# assert cap.isOpened()
# Usage
capture_thread = VideoCaptureThread(device, camID, endSignal) # src can be a filepath or a device index
capture_thread.start()
# # To stop the thread
# capture_thread.stop()
# Display Process
def runViewer():
while endSignal != 1:
# print("Qlen: ", qqq.qsize())
if qqq.empty() != True:
frame = qqq.get()
fy, fx, _  = frame.shape 
frame = cv2.resize(frame,(int(2*fx),int(2*fy)))
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
while qqq.qsize() > 0: # Empty the Q
qqq.get()
# Signal Handler
def signal_handler(sig, arg2):
print("Exiting...")
endSignal.value = 1
sys.exit(0)

#### MAIN ####
if __name__ == '__main__':
signal.signal(signal.SIGINT, signal_handler)
processes = []
idx = 0
# Setup the cameras
for device, capDevice in vidDict.items():
if capDevice.isOpened():
processes.append(Process(target=runCamera, args=(capDevice,idx)))
idx = idx + 1
else:
print(f"Ejecting: {device}")
numProcesses = len(processes)
print(f"Processes: {numProcesses}")
processes.append(Process(target=runViewer))
# Launch the processes
for process in processes:
process.start()
# Keyboard control
while endSignal != 1:
if keyboard.is_pressed('d'):  # if key 'q' is pressed 
print('You Pressed d Key!')
selectedCam.value = (selectedCam.value + 1) % numProcesses
time.sleep(250/1000)
if keyboard.is_pressed('a'):  # if key 'q' is pressed 
print('You Pressed a Key!')
selectedCam.value = (selectedCam.value - 1) % numProcesses
time.sleep(250/1000)
# Graceful shutdown?
print("START END")

for process in processes:
process.join()
for device, capDevice in vidDict.items():
capDevice.release()
# Destroy all the windows
cv2.destroyAllWindows()

这个代码似乎支持多达5个相机没有问题。扩展到10种工作，但有些相机似乎不发送数据。线程和多处理的结合是为了让下一帧准备好立即添加到队列中，因此在切换摄像机时不会出现暂停，如果我们必须经历整个cap设置和读取过程的话。

谢谢。

Answer 1

通过使用多线程在单独的线程中运行每个相机捕获。在这个方法中，当其他线程正在捕获下一个帧时，主线程可以继续处理当前显示的帧。