如何根據 OpenCV VideoWriter 的觸發器開始和停止保存視頻幀

Question

我正在構建一個通過 RTSP 記錄來自 IP 攝像機的幀的應用程序。

我的引擎負責將視頻保存在 mp4 中，Opencv VideoWriter 運行良好。 我正在尋找的是創建一個 startRecord 和一個 stopRecord 類方法，它們將根據觸發器分別開始和停止記錄（它可能是我傳遞給線程的參數）。 有誰知道做這種事情的最好方法是什么？

這是我的課：

from threading import Thread
import cv2
import time
import multiprocessing
import threading
class RTSPVideoWriterObject(object):
    def __init__(self, src=0):
        # Create a VideoCapture object
        self.capture = cv2.VideoCapture(src)

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

    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 endRecord(self):
        self.capture.release()
        self.output_video.release()
        exit(1)

    def startRecord(self,endRec):

        self.frame_width = int(self.capture.get(3))
        self.frame_height = int(self.capture.get(4))
        self.codec = cv2.VideoWriter_fourcc(*'mp4v')
        self.output_video = cv2.VideoWriter('fileOutput.mp4', self.codec, 30, (self.frame_width, self.frame_height))
        while True:          
            try:
                self.output_video.write(self.frame)
                if endRec:
                    self.endRecord()
            except AttributeError:
                pass




if __name__ == '__main__':

    rtsp_stream_link = 'rtsp://foo:192.5545....'
    video_stream_widget = RTSPVideoWriterObject(rtsp_stream_link)

    stop_threads = False
    t1 = threading.Thread(target = video_stream_widget.startRecord, args =[stop_threads]) 
    t1.start() 
    time.sleep(15)
    stop_threads = True

正如您在主 I 閱讀框架中看到的那樣，並將它們存儲在一個單獨的線程中。 然后我開始記錄（記錄方法是無限循環，因此阻塞），然后在 15 秒后，我試圖傳遞一個“stop_record”參數以正確停止記錄。

部分代碼來自Storing RTSP stream as video file with OpenCV VideoWriter

有人有想法嗎？ 我讀了很多 OpenCV 對於多線程來說可能非常棘手

N。

Answer 1

不是將參數傳遞給線程，而是使用類中的內部標志來確定何時開始/停止記錄。 觸發器可以像按空格鍵開始/停止錄制一樣簡單。 當按下空格鍵時，它會切換一個內部變量，將self.record設為True以開始錄制，設為False以停止錄制。 具體來說，要檢查何時按下空格鍵，您可以檢查cv2.waitKey()返回的鍵值是否為32 。 如果您想要基於任何其他鍵的觸發器，請查看此帖子以確定鍵代碼。 這是使用空格鍵開始/停止錄制視頻的快速示例：

from threading import Thread
import cv2

class RTSPVideoWriterObject(object):
    def __init__(self, src=0):
        # Create a VideoCapture object
        self.capture = cv2.VideoCapture(src)
        self.record = True

        # 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(*'mp4v')
        self.output_video = cv2.VideoWriter('output.mp4', 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()

    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('frame', self.frame)
            if self.record:
                self.save_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)
        # Press spacebar to start/stop recording
        elif key == 32:
            if self.record:
                self.record = False
                print('Stop recording')
            else:
                self.record = True
                print('Start recording')

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

if __name__ == '__main__':
    rtsp_stream_link = 'Your stream link!'
    video_stream_widget = RTSPVideoWriterObject(rtsp_stream_link)
    while True:
        try:
            video_stream_widget.show_frame()
        except AttributeError:
            pass

Answer 2

我通過在類中創建一個全局變量來解決這個問題，對於你的案例 endRec。