由于項目需要進行數(shù)據(jù)采集赏表，從攝像頭讀取后匈仗，將讀取的每幀數(shù)據(jù)進行保存視頻。在使用過程中悠轩，發(fā)現(xiàn)采集的生成的視頻達不到指定的fps，存在丟幀現(xiàn)象鉴象。經(jīng)過排查，在寫視頻write(frame)存在IO耗時偏高牛欢，每幀處理耗時長了傍睹，導(dǎo)致掉幀犹菱。特別在1080p,30fps的寫入視頻對CPU占用都較高腊脱。
為了解決這個問題陕凹，將單線程改為多線程進行 讀寫分離 處理數(shù)據(jù)幀杜耙，將讀出的視頻幀泥技，放入FIFO隊列,寫視頻線程從隊列中讀取數(shù)據(jù)幀珊豹，按照指定幀率進行寫入保存視頻店茶。
代碼如下：

import os
import time

import cv2
import datetime
import configparser
import csv


import queue

import threading

thread_exit = False
ready = False

q = queue.Queue()

class myThread(threading.Thread):
    def __init__(self, camera_id, img_width, img_height, fps):
        super(myThread, self).__init__()
        self.camera_id = camera_id
        self.img_width = img_width
        self.img_height = img_height
        self.fps = fps

        self.cap = cv2.VideoCapture(self.camera_id)

        print("攝像頭默認幀率:{}".format(self.cap.get(cv2.CAP_PROP_FPS)))
        print("攝像頭設(shè)置幀率:{}".format(self.fps))
        ret = self.cap.set(5, self.fps)        # 設(shè)置視頻讀取幀率
        print("攝像頭設(shè)置后幀率:{},{}".format(ret, self.cap.get(cv2.CAP_PROP_FPS)))

        self.cap.set(3, self.img_width)  # 設(shè)置視頻的寬
        self.cap.set(4, self.img_height)  # 設(shè)置視頻的高

        print("攝像頭默認編解碼:{}".format(self.cap.get(cv2.CAP_PROP_FOURCC)))
        fourcc = cv2.VideoWriter_fourcc('M', 'J', 'P', 'G')
        self.cap.set(6, fourcc)  # 設(shè)置解碼格式
        print("攝像頭設(shè)置后編解碼:{}".format(self.cap.get(cv2.CAP_PROP_FOURCC)))

        self.img_width = int(self.cap.get(cv2.CAP_PROP_FRAME_WIDTH))  # 重新獲取最大的分辨率寬
        self.img_height = int(self.cap.get(cv2.CAP_PROP_FRAME_HEIGHT))  # 重新獲取最大的分辨率高
        self.fps = int(self.cap.get(cv2.CAP_PROP_FPS))                # 獲取支持的fps


    def run(self):
        global thread_exit
        global ready
        global q
       
        frame_count = 0
        str_time = datetime.datetime.now().strftime('%Y%m%d%H%M%S')
        f = open(str_time + '.csv', 'w', encoding='utf-8', newline='')
        header = ['Frame', 'DateTime']
        writer = csv.writer(f)
        writer.writerow(header)
        while not thread_exit:
            ret, frame = self.cap.read()
            if ret:
                print(self.cap.get(cv2.CAP_PROP_POS_MSEC))
              
                font = cv2.FONT_HERSHEY_SIMPLEX
                text = 'Width: ' + str(self.img_width) + ' Height:' + str(self.img_height)

                datet = str(datetime.datetime.now())
                str_date = datet.replace('.', ' ')  # .分隔會導(dǎo)致csv文件格式顯示不對,需要格式處理
                # datet = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S %f')[:-3] # .分隔會導(dǎo)致csv文件格式顯示不對需要格式處理
                frame = cv2.putText(frame, text, (10, 50), font, 0.5,
                                    (0, 255, 255), 2, cv2.LINE_AA)
                frame = cv2.putText(frame, datet, (10, 100), font, 1,
                                    (0, 255, 255), 2, cv2.LINE_AA)
                my_list = [frame_count, str_date]
                writer.writerow(my_list)

                q.put(frame)
                ready = True
                frame_count = frame_count + 1
            else:
                f.close()
                thread_exit = True
                self.cap.release()


def main():
    # 默認設(shè)置
    id = 0
    width = 640
    height = 480
    fps = 30

    status = os.path.exists("config.ini")
    if status == True:
        config = configparser.ConfigParser()
        config.read("config.ini")

        config.sections()
        config.options("camera")
        id = config.getint("camera", "id")
        width = config.getint("camera", "width")
        height = config.getint("camera", "height")
        fps = config.getint("camera", "fps")
        print("配置文件中讀取配置")

    global thread_exit
    global ready
    global q

    thread = myThread(id, width, height,  fps)
    thread.start()

    tmp_list = []

    # 構(gòu)建視頻保存的對象
    fourcc = cv2.VideoWriter_fourcc('M', 'J', 'P', 'G')  
    str_time = datetime.datetime.now().strftime('%Y%m%d%H%M%S')

    out = cv2.VideoWriter(str_time + ".avi", fourcc, thread.fps, (thread.img_width, thread.img_height))

    interval = 1 / thread.fps   # 毫秒為單位
    print(interval)

    while not thread_exit:
        if ready:
            start = time.time()
            print(start)

            print(q.qsize())
            q_start = time.time()
            frame = q.get()
            q_end = time.time()
            qt = (round(q_end * 1000) - round(q_start * 1000)) / 1000
            print("隊列獲取數(shù)據(jù)耗時:{}".format(qt))

            cv2.imshow('Video', frame)

            start_time = time.time()
            out.write(frame)  # 保存視頻
            end_time = time.time()
            tt = (round(end_time * 1000) - round(start_time * 1000)) / 1000
            print("寫耗時:{}".format(tt))

            end = time.time()
            print(end)

            t = (round(end * 1000) - round(start * 1000)) / 1000
            print(t)
            # if t < interval:
            #     time.sleep(interval-t)

            if cv2.waitKey(1) & 0xFF == ord('q'):
                thread_exit = True
                out.release()
                cv2.destroyAllWindows()


        else:
            continue

    thread.join()



if __name__ == "__main__":
    main()