树莓派 4 带 2 cam USB答案

【问题标题】：Raspberry pi 4 with 2 cam USB树莓派 4 带 2 cam USB
【发布时间】：2020-09-16 05:04:03
【问题描述】：

我正在尝试在我的 Raspberry pi 中使用我的代码，但我只能在计算机上看到摄像头的图像我已经可以看到两个 USB 摄像头的图像有人知道发生了什么，你能帮忙吗我？

import threading

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)
    if cam.isOpened():  # try to get the first frame
        rval, frame = cam.read()
    else:
        rval = False

    while rval:
        cv2.imshow(previewName, frame)
        rval, frame = cam.read()
        key = cv2.waitKey(20)
        if key == 27:  # exit on ESC
            break
    cv2.destroyWindow(previewName)

thread1 = camThread("Camera 1", 0)
thread2 = camThread("Camera 2", 1)
thread1.start()
thread2.start()

外壳：

Python 3.7.3 (/usr/bin/python3)

>>> %Run cameraa.py

Starting Camera 1Starting Camera 2

/*error*/
>>> Xlib: charsets ISO8859-1:GR and ISO8859-1:GR have the same CT sequence
Xlib: charsets JISX0201.1976-0:GR and JISX0201.1976-0:GR have the same CT sequence
Xlib: charsets JISX0212.1990-0:GL and JISX0212.1990-0:GL have the same CT sequence
Xlib: charsets CNS11643.1986-1:GR and CNS11643.1986-1:GR have the same CT sequence
Xlib: charsets CNS11643.1992-3:GR and CNS11643.1992-3:GR have the same CT sequence
Xlib: charsets CNS11643.1992-5:GR and CNS11643.1992-5:GR have the same CT sequence
Xlib: charsets CNS11643.1992-7:GR and CNS11643.1992-7:GR have the same CT sequence
Xlib: charsets BIG5-E0:GL and BIG5-E0:GL have the same CT sequence
[ WARN:0] global /home/pi/opencv_build/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video1): can't open camera by index

【问题讨论】：

标签： python python-3.x raspberry-pi raspbian raspberry-pi4

【解决方案1】：

同时与 X11（或任何其他 UI 后端）交互并不是一个好主意。详情请见here。

专门针对 OpenCV，您可以查看此问题：

您应该只从“主”线程与 UI 交互。

https://github.com/opencv/opencv/issues/8407

因此，解决方法是仅在主线程上使用imshow 和waitKey。（而不是超过两个线程）。换句话说，将三个调用（两个imshows 和一个waitKey）移动到主线程，并同步对两个Mat 对象的访问，您可以用来在主线程和其他两个线程之间共享数据.

【讨论】：