行空板使用摄像头OpenCV错误

报错段代码：cap = cv2.VideoCapture(0)
def video_head():    u_gui.clear()
    cap = cv2.VideoCapture(0)
    cap.set(cv2.CAP_PROP_BUFFERSIZE,1)
    cap.open(0)
    while cap.isOpened():
        ret,img = cap.read()
        if ret:
            h,w,c = img.shape
            w1 = h*240//320
            x1 = (w-w1)//2
            img = img[:,x1:x1+w1]
            img2 = cv2.resize(img, (240, 320))
        if button_b.is_pressed():
            cap.release()
            break
报错信息：
[ WARN:0@145.288] global cap_v4l.cpp:982 open VIDEOIO(V4L2:/dev/video0): can't open camera by index[ERROR:0@145.292] global obsensor_uvc_stream_channel.cpp:156 getStreamChannelGroup Camera index out of range[ WARN:0@145.293] global cap_v4l.cpp:982 open VIDEOIO(V4L2:/dev/video0): can't open camera by index[ERROR:0@145.296] global obsensor_uvc_stream_channel.cpp:156 getStreamChannelGroup Camera index out of range