python - opencv python多线程视频采集

Question

我正在尝试读取 2 个视频文件并同时在单独的 Windows 中显示它们。这是我的代码:

import threading
import cv2
threadLock=threading.Lock()
class myThread (threading.Thread):
    maxRetries=20
    def __init__(self, threadID, name,video_url):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.video_url=video_url

    def attemptRead(self,cvVideo):
        threadLock.acquire()
        (isRead,cvImage)=cvVideo.read()
        threadLock.release()
        if isRead==False:
            count=1
            while isRead==False and count<myThread.maxRetries:
                threadLock.acquire()
                (isRead,cvImage)=cvVideo.read()
                threadLock.release()
                print self.name+' try no: ',count
                count+=1
        return (isRead,cvImage)

    def run(self):
        print "Starting " + self.name
        windowName = self.name
        cv2.namedWindow(windowName)
        cvVideo = cv2.VideoCapture(self.video_url)


        while True:
            (isRead,cvImage)=self.attemptRead(cvVideo)
            if isRead==False:
                break
            cv2.imshow(windowName,cvImage)
            key=cv2.waitKey(50)
            if key==27:
                break

        cv2.destroyWindow(windowName)
        print self.name + "Exiting"

def main():
    thread1 = myThread(1, "Thread1",'C:/Traffic Pics/Videos/Panjim Capture.mp4')
    thread2 = myThread(2, "Thread2",'C:/Traffic Pics/Videos/Miramar Capture.mp4')

    thread1.start()
    thread2.start()

print "Exiting Main Thread"

if __name__ == '__main__':
    main()

发生的事情是，只有 线程 2 窗口正在显示。 线程 1 在尝试读取超过 ma​​x_retries 限制(在我的例子中为 10)之后退出。问题是虽然我创建了单独的 cvVideo 对象，但我似乎无法同时使用它们。可能是什么问题？

Answer 1

*edit:我将把代码留在下面，但我猜你遇到了编解码器问题？我安装了 xvid 编解码器(样本 Megamind.avi 就是用它编码的)，程序在运行 megamind 视频的任一线程或两个线程上都能正常工作。你能让 megamind 视频在单线程版本中运行吗？

这里是 an SO post on opencv video codecs以防万一。这是 xvid download我用过的(k-lite 对我不起作用)。

---

你写的代码基本上对我有用。对于您和任何其他想要尝试的人，我做了以下事情:

• 应用 PEP 8 建议
• 删除了不必要的读取尝试代码(这也删除了在工作视频的最后一帧之后误导性的线程重读警告)
• 使用了可能每个使用 opencv 的人都有的视频文件
• 至少在我的系统上删除了对 opencv 似乎无关紧要的线程锁定
• 移动了一些其他的小东西

VideoCapture.read 可能会出现其他错误，这会使 read_attempt 方法值得，但我只能找到 the two errors the docs mention .对于那些它只返回代码已经测试过的 false。

import os
import threading

import cv2

my_opencv_path = "C:/opencv2.4.3"
video_path_1 = os.path.join(my_opencv_path, "samples", "cpp", "tutorial_code",
                            "HighGUI", "video-input-psnr-ssim", "video",
                            "Megamind.avi")
video_path_2 = os.path.join(my_opencv_path, "samples", "c", "tree.avi")
assert os.path.isfile(video_path_1)
assert os.path.isfile(video_path_2)


class MyThread (threading.Thread):
    maxRetries = 20

    def __init__(self, thread_id, name, video_url, thread_lock):
        threading.Thread.__init__(self)
        self.thread_id = thread_id
        self.name = name
        self.video_url = video_url
        self.thread_lock = thread_lock

    def run(self):
        print "Starting " + self.name
        window_name = self.name
        cv2.namedWindow(window_name)
        video = cv2.VideoCapture(self.video_url)
        while True:
            # self.thread_lock.acquire()  # These didn't seem necessary
            got_a_frame, image = video.read()
            # self.thread_lock.release()
            if not got_a_frame:  # error on video source or last frame finished
                break
            cv2.imshow(window_name, image)
            key = cv2.waitKey(50)
            if key == 27:
                break
        cv2.destroyWindow(window_name)
        print self.name + " Exiting"


def main():
    thread_lock = threading.Lock()
    thread1 = MyThread(1, "Thread 1", video_path_1, thread_lock)
    thread2 = MyThread(2, "Thread 2", video_path_2, thread_lock)
    thread1.start()
    thread2.start()
    print "Exiting Main Thread"

if __name__ == '__main__':
    main()