1. 개발기록

import cv2
import threading
import sys
from PyQt5 import QtWidgets
from PyQt5 import QtGui
from PyQt5 import QtCore

running = False

def run():
    global running
    cap = cv2.VideoCapture(0)
    width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
    height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
    label.resize(width, height)
    while running:
        ret, img = cap.read()
        if ret:
            img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
            h,w,c = img.shape
            qImg = QtGui.QImage(img.data, w, h, w*c, QtGui.QImage.Format_RGB888)
            pixmap = QtGui.QPixmap.fromImage(qImg)
            label.setPixmap(pixmap)
        else:
            QtWidgets.QMessageBox.about(win, "Error", "Cannot read frame.")
            print("cannot read frame.")
            break
    cap.release()
    print("Thread end.")


def stop():
    global running
    running = False
    print("stoped..")

def start():
    global running
    running = True
    th = threading.Thread(target=run)
    th.start()
    print("started..")

def save():
    pass

def onExit():
    print("exit")
    stop()

app = QtWidgets.QApplication([])
win = QtWidgets.QWidget()
vbox = QtWidgets.QVBoxLayout()
label = QtWidgets.QLabel()
btn_start = QtWidgets.QPushButton("Camera On")
btn_stop = QtWidgets.QPushButton("Camera Off")
btn_save = QtWidgets.QPushButton("Camera Save")

vbox.addWidget(label)
vbox.addWidget(btn_start)
vbox.addWidget(btn_stop)
win.setLayout(vbox)
win.show()

btn_start.clicked.connect(start)
btn_stop.clicked.connect(stop)
btn_save.clicked.connect(save)
app.aboutToQuit.connect(onExit)

sys.exit(app.exec_())

여기서 카메라를 두개 더 늘리는 것 까진 어떻게 했는데,
저장기능은 아직 구현하지 못함 ㅠㅠ..