如何使用OpenCV捕获多路摄像头流？

Question

我必须拼接从许多(9)个相机捕获的图像。最初，我尝试以15帧/秒的速率从2个摄像头捕捉帧。然后，我连接了4个摄像头(我也使用了外部供电的USB集线器来提供足够的电力)，但我只能看到一个流。

为了进行测试，我使用了以下脚本：

import numpy as np
import cv2
import imutils

index = 0
arr = []
while True:
    cap = cv2.VideoCapture(index)

    if not cap.read()[0]:
        break
    else:
        arr.append(index)
    cap.release()
    index += 1

video_captures = [cv2.VideoCapture(idx) for idx in arr]

while True:
    # Capture frame-by-frame
    frames = []
    frames_preview = []

    for i in arr:
        # skip webcam capture
        if i == 1: continue
        ret, frame = video_captures[i].read()
        if ret:
            frames.append(frame)
            small = cv2.resize(frame, (0, 0), fx=0.25, fy=0.25)
            frames_preview.append(small)

    for i, frame in enumerate(frames_preview):
        cv2.imshow('Cam {}'.format(i), frame)


    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything is done, release the capture
for video_capture in video_captures:
    video_capture.release()
cv2.destroyAllWindows()

摄像头的数量有限制吗？谁知道从多个摄像头捕获帧的正确方法是什么？

Answer 1

​

​

要使用OpenCV捕获多个流，我建议使用线程，它可以通过减轻对单独线程的繁重I/O操作来提高性能。由于使用以下命令访问网络摄像头/IP/RTSP流

是一个分块操作，我们的主程序会被卡住，直到从摄像头设备读取到帧。如果你有多个流，这个延迟肯定是可见的。为了解决这个问题，我们可以使用线程来产生另一个线程，以便并行地使用一个双队列来获取帧，而不是依赖单个线程来按顺序获取帧。线程允许连续读取帧，而不会影响主程序的性能。使用线程和OpenCV捕获单个流的想法来自

来自摄像头的Python OpenCV多线程流

..。

但如果你想捕获

多流

，仅有OpenCV是不够的。您可以将OpenCV与图形用户界面框架结合使用，将每个图像拼接到一个漂亮的显示上。我将使用

PyQt4

作为框架，

qdarkstyle

对于GUI CSS，和

imutils

用于OpenCV便利函数。

这是我目前使用的相机GUI的一个非常精简的版本，没有占位符图像、凭证管理登录页面和相机切换功能。我保留了自动摄像头重新连接功能，以防互联网中断或摄像头连接中断。我只有8个摄像头，如上图所示，但添加另一个摄像头非常简单，应该不会影响性能。此摄像头GUI目前的性能约为

FPS所以它是实时的。您可以使用PyQt布局轻松地重新排列布局，因此请随意修改代码！记住要更改流链接！

from PyQt4 import QtCore, QtGui
import qdarkstyle
from threading import Thread
from collections import deque
from datetime import datetime
import time
import sys
import cv2
import imutils

class CameraWidget(QtGui.QWidget):
    """Independent camera feed
    Uses threading to grab IP camera frames in the background

    @param width - Width of the video frame
    @param height - Height of the video frame
    @param stream_link - IP/RTSP/Webcam link
    @param aspect_ratio - Whether to maintain frame aspect ratio or force into fraame
    """

    def __init__(self, width, height, stream_link=0, aspect_ratio=False, parent=None, deque_size=1):
        super(CameraWidget, self).__init__(parent)

        # Initialize deque used to store frames read from the stream
        self.deque = deque(maxlen=deque_size)

        # Slight offset is needed since PyQt layouts have a built in padding
        # So add offset to counter the padding 
        self.offset = 16
        self.screen_width = width - self.offset
        self.screen_height = height - self.offset
        self.maintain_aspect_ratio = aspect_ratio

        self.camera_stream_link = stream_link

        # Flag to check if camera is valid/working
        self.online = False
        self.capture = None
        self.video_frame = QtGui.QLabel()

        self.load_network_stream()

        # Start background frame grabbing
        self.get_frame_thread = Thread(target=self.get_frame, args=())
        self.get_frame_thread.daemon = True
        self.get_frame_thread.start()

        # Periodically set video frame to display
        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.set_frame)
        self.timer.start(.5)

        print('Started camera: {}'.format(self.camera_stream_link))

    def load_network_stream(self):
        """Verifies stream link and open new stream if valid"""

        def load_network_stream_thread():
            if self.verify_network_stream(self.camera_stream_link):
                self.capture = cv2.VideoCapture(self.camera_stream_link)
                self.online = True
        self.load_stream_thread = Thread(target=load_network_stream_thread, args=())
        self.load_stream_thread.daemon = True
        self.load_stream_thread.start()

    def verify_network_stream(self, link):
        """Attempts to receive a frame from given link"""

        cap = cv2.VideoCapture(link)
        if not cap.isOpened():
            return False
        cap.release()
        return True

    def get_frame(self):
        """Reads frame, resizes, and converts image to pixmap"""

        while True:
            try:
                if self.capture.isOpened() and self.online:
                    # Read next frame from stream and insert into deque
                    status, frame = self.capture.read()
                    if status:
                        self.deque.append(frame)
                    else:
                        self.capture.release()
                        self.online = False
                else:
                    # Attempt to reconnect
                    print('attempting to reconnect', self.camera_stream_link)
                    self.load_network_stream()
                    self.spin(2)
                self.spin(.001)
            except AttributeError:
                pass

    def spin(self, seconds):
        """Pause for set amount of seconds, replaces time.sleep so program doesnt stall"""

        time_end = time.time() + seconds
        while time.time() < time_end:
            QtGui.QApplication.processEvents()

    def set_frame(self):
        """Sets pixmap image to video frame"""

        if not self.online:
            self.spin(1)
            return

        if self.deque and self.online:
            # Grab latest frame
            frame = self.deque[-1]

            # Keep frame aspect ratio
            if self.maintain_aspect_ratio:
                self.frame = imutils.resize(frame, width=self.screen_width)
            # Force resize
            else:
                self.frame = cv2.resize(frame, (self.screen_width, self.screen_height))

            # Add timestamp to cameras
            cv2.rectangle(self.frame, (self.screen_width-190,0), (self.screen_width,50), color=(0,0,0), thickness=-1)
            cv2.putText(self.frame, datetime.now().strftime('%H:%M:%S'), (self.screen_width-185,37), cv2.FONT_HERSHEY_SIMPLEX, 1.2, (255,255,255), lineType=cv2.LINE_AA)

            # Convert to pixmap and set to video frame
            self.img = QtGui.QImage(self.frame, self.frame.shape[1], self.frame.shape[0], QtGui.QImage.Format_RGB888).rgbSwapped()
            self.pix = QtGui.QPixmap.fromImage(self.img)
            self.video_frame.setPixmap(self.pix)

    def get_video_frame(self):
        return self.video_frame

def exit_application():
    """Exit program event handler"""

    sys.exit(1)

if __name__ == '__main__':

    # Create main application window
    app = QtGui.QApplication([])
    app.setStyleSheet(qdarkstyle.load_stylesheet_pyqt())
    app.setStyle(QtGui.QStyleFactory.create("Cleanlooks"))
    mw = QtGui.QMainWindow()
    mw.setWindowTitle('Camera GUI')
    mw.setWindowFlags(QtCore.Qt.FramelessWindowHint)

    cw = QtGui.QWidget()
    ml = QtGui.QGridLayout()
    cw.setLayout(ml)
    mw.setCentralWidget(cw)
    mw.showMaximized()

    # Dynamically determine screen width/height
    screen_width = QtGui.QApplication.desktop().screenGeometry().width()
    screen_height = QtGui.QApplication.desktop().screenGeometry().height()

    # Create Camera Widgets 
    username = 'Your camera username!'
    password = 'Your camera password!'

    # Stream links
    camera0 = 'rtsp://{}:{}@192.168.1.43:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera1 = 'rtsp://{}:{}@192.168.1.45/axis-media/media.amp'.format(username, password)
    camera2 = 'rtsp://{}:{}@192.168.1.47:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera3 = 'rtsp://{}:{}@192.168.1.40:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera4 = 'rtsp://{}:{}@192.168.1.44:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera5 = 'rtsp://{}:{}@192.168.1.42:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera6 = 'rtsp://{}:{}@192.168.1.46:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)
    camera7 = 'rtsp://{}:{}@192.168.1.41:554/cam/realmonitor?channel=1&subtype=0'.format(username, password)

    # Create camera widgets
    print('Creating Camera Widgets...')
    zero = CameraWidget(screen_width//3, screen_height//3, camera0)
    one = CameraWidget(screen_width//3, screen_height//3, camera1)
    two = CameraWidget(screen_width//3, screen_height//3, camera2)
    three = CameraWidget(screen_width//3, screen_height//3, camera3)
    four = CameraWidget(screen_width//3, screen_height//3, camera4)
    five = CameraWidget(screen_width//3, screen_height//3, camera5)
    six = CameraWidget(screen_width//3, screen_height//3, camera6)
    seven = CameraWidget(screen_width//3, screen_height//3, camera7)

    # Add widgets to layout
    print('Adding widgets to layout...')
    ml.addWidget(zero.get_video_frame(),0,0,1,1)
    ml.addWidget(one.get_video_frame(),0,1,1,1)
    ml.addWidget(two.get_video_frame(),0,2,1,1)
    ml.addWidget(three.get_video_frame(),1,0,1,1)
    ml.addWidget(four.get_video_frame(),1,1,1,1)
    ml.addWidget(five.get_video_frame(),1,2,1,1)
    ml.addWidget(six.get_video_frame(),2,0,1,1)
    ml.addWidget(seven.get_video_frame(),2,1,1,1)

    print('Verifying camera credentials...')

    mw.show()

    QtGui.QShortcut(QtGui.QKeySequence('Ctrl+Q'), mw, exit_application)

    if(sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()