使用 Opencv Python 多线程录制视频

Question

在窗口上显示流的线程中进行多线程处理时，我试图在 python 中使用 opencv 录制视频。 我对多线程相当陌生，我不确定我无法录制视频的原因是什么。 我保存了一个文件，但其中没有流。 非常感谢指针。这是我的代码：

import cv2
import os
import threading
import shutil
import json
import re
import datetime
import time
now=datetime.datetime.now()



class camThread(threading.Thread):
    def __init__(self, previewName, camID):
        threading.Thread.__init__(self)
        self.previewName = previewName

        self.camID = camID

    def run(self):
        print("Starting " + self.previewName)
        camPreview(self.previewName, self.camID)

def camPreview(previewName, camID):
    cv2.namedWindow(previewName)
    cam = cv2.VideoCapture(camID)
    cam.set(cv2.CAP_PROP_FRAME_WIDTH, 480)
    cam.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)
    if cam.isOpened():
        rval, frame = cam.read()
        frame_width = int(cam.get(3))
        frame_height = int(cam.get(4))

    else:
        rval = False

    while rval:
        cv2.namedWindow(previewName, cv2.WINDOW_NORMAL)
        if (camID == 2):
            frame= cv2.flip(frame,-1)
       # cv2.setWindowProperty(previewName, cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN)
        cv2.imshow(previewName, frame)
      # cam.set(CV_CAP_PROP_SETTINGS, 0)
        rval, frame = cam.read()

        key = cv2.waitKey(20)
        if key == 115 :
            Cam1="Cam"+str(camID)+"_"+timestr
            ts=datetime.datetime.now()
            filename="{}.avi".format(Cam1+ts.strftime("%Y%m%d_%H-%M-%S"))
            out=cv2.VideoWriter(filename,cv2.VideoWriter_fourcc('M','J', 'P','G'),10,(480,720))
            out.write(frame)
            if key == 27:
              print("Stopping recording")
              break
        if key == 27:  # exit on ESC
            break
    cv2.destroyWindow(previewName)

# Create threads as follows
thread1 = camThread("Camera 1", 0)
thread2 = camThread("Camera 2", 2)
thread3 = camThread("Camera 3", 3)
timestr=str(now.strftime("%Y%m%d_%H-%M-%S"))

print("Working Directory:")
print(timestr)

#thread1.start()
thread2.start()
thread3.start()
print()
print("Active threads", threading.activeCount())

Answer 1

我认为您在正确的轨道上，但我无法使用您的代码保存文件。 这是一个使用多线程获取帧的视频流到视频小部件。 每个摄像头流有两个线程：

• 线程 #1 - 专用于仅从相机流中读取帧。
• 线程 #2 - 专用于处理帧（显示和写入）。

我们将阅读帧与显示/写入分开，因为cv2.VideoCapture.read()是一个阻塞操作。 因此，我们在自己的独立线程中读取帧，通过减少 I/O 操作引起的延迟来“提高”FPS。 此外，通过将帧捕获隔离到它自己的线程，总会有一个帧准备好被处理，而不必等待 I/O 操作完成并返回一个新的帧。 在我们专用于处理的第二个线程中，我们现在可以自由地显示每一帧并将其保存到我们的输出文件中。

此外，通过将所有这些都封装到单个对象中，我们可以为每个相机创建一组线程，无论使用多少个相机，这些线程都可以轻松缩放。 由于每个相机流都在后台线程中生成，因此我们必须保持主线程处于活动状态。 请务必将src字符串更改为您自己的相机。 这是同时录制三个视频流的示例。

from threading import Thread
import cv2
import time

class VideoWriterWidget(object):
    def __init__(self, video_file_name, src=0):
        # Create a VideoCapture object
        self.frame_name = str(src)
        self.video_file = video_file_name
        self.video_file_name = video_file_name + '.avi'
        self.capture = cv2.VideoCapture(src)

        # Default resolutions of the frame are obtained (system dependent)
        self.frame_width = int(self.capture.get(3))
        self.frame_height = int(self.capture.get(4))

        # Set up codec and output video settings
        self.codec = cv2.VideoWriter_fourcc('M','J','P','G')
        self.output_video = cv2.VideoWriter(self.video_file_name, self.codec, 30, (self.frame_width, self.frame_height))

        # Start the thread to read frames from the video stream
        self.thread = Thread(target=self.update, args=())
        self.thread.daemon = True
        self.thread.start()

        # Start another thread to show/save frames
        self.start_recording()
        print('initialized {}'.format(self.video_file))

    def update(self):
        # Read the next frame from the stream in a different thread
        while True:
            if self.capture.isOpened():
                (self.status, self.frame) = self.capture.read()

    def show_frame(self):
        # Display frames in main program
        if self.status:
            cv2.imshow(self.frame_name, self.frame)

        # Press Q on keyboard to stop recording
        key = cv2.waitKey(1)
        if key == ord('q'):
            self.capture.release()
            self.output_video.release()
            cv2.destroyAllWindows()
            exit(1)

    def save_frame(self):
        # Save obtained frame into video output file
        self.output_video.write(self.frame)

    def start_recording(self):
        # Create another thread to show/save frames
        def start_recording_thread():
            while True:
                try:
                    self.show_frame()
                    self.save_frame()
                except AttributeError:
                    pass
        self.recording_thread = Thread(target=start_recording_thread, args=())
        self.recording_thread.daemon = True
        self.recording_thread.start()

if __name__ == '__main__':
    src1 = 'Your link1'
    video_writer_widget1 = VideoWriterWidget('Camera 1', src1)
    src2 = 'Your link2'
    video_writer_widget2 = VideoWriterWidget('Camera 2', src2)
    src3 = 'Your link3'
    video_writer_widget3 = VideoWriterWidget('Camera 3', src3)

    # Since each video player is in its own thread, we need to keep the main thread alive.
    # Keep spinning using time.sleep() so the background threads keep running
    # Threads are set to daemon=True so they will automatically die 
    # when the main thread dies
    while True:
        time.sleep(5)

Answer 2

from threading import Thread
import cv2
import time

class VideoWriterWidget(object):
    def __init__(self, video_file_name, src=0):
        # Create a VideoCapture object
        self.frame_name = str(src) # if using webcams, else just use src as it is.
        self.video_file = video_file_name
        self.video_file_name = video_file_name + '.avi'
        self.capture = cv2.VideoCapture(src)

        # Default resolutions of the frame are obtained (system dependent)
        self.frame_width = int(self.capture.get(3))
        self.frame_height = int(self.capture.get(4))

        # Set up codec and output video settings
        self.codec = cv2.VideoWriter_fourcc('M','J','P','G')
        self.output_video = cv2.VideoWriter(self.video_file_name, self.codec, 30, (self.frame_width, self.frame_height))

        # Start the thread to read frames from the video stream
        self.thread = Thread(target=self.update, args=())
        self.thread.daemon = True
        self.thread.start()

        # Start another thread to show/save frames
        self.start_recording()
        print('initialized {}'.format(self.video_file))

    def update(self):
        # Read the next frame from the stream in a different thread
        while True:
            if self.capture.isOpened():
                (self.status, self.frame) = self.capture.read()

    def show_frame(self):
        # Display frames in main program
        if self.status:
            cv2.imshow(self.frame_name, self.frame)

        # Press Q on keyboard to stop recording
        key = cv2.waitKey(1)
        if key == ord('q'):
            self.capture.release()
            self.output_video.release()
            cv2.destroyAllWindows()
            exit(1)

    def save_frame(self):
        # Save obtained frame into video output file
        self.output_video.write(self.frame)

    def start_recording(self):
        # Create another thread to show/save frames
        def start_recording_thread():
            while True:
                try:
                    self.show_frame()
                    self.save_frame()
                except AttributeError:
                    pass
        self.recording_thread = Thread(target=start_recording_thread, args=())
        self.recording_thread.daemon = True
        self.recording_thread.start()

if __name__ == '__main__':
    src1 = 'Your link1'
    video_writer_widget1 = VideoWriterWidget('Camera 1', src1)
    src2 = 'Your link2'
    video_writer_widget2 = VideoWriterWidget('Camera 2', src2)
    src3 = 'Your link3'
    video_writer_widget3 = VideoWriterWidget('Camera 3', src3)

    # Since each video player is in its own thread, we need to keep the main thread alive.
    # Keep spinning using time.sleep() so the background threads keep running
    # Threads are set to daemon=True so they will automatically die 
    # when the main thread dies
    while True:
        time.sleep(5)