OpenCv无法按索引打开摄影机

Question

操作系统

Ubuntu 20.04

OPENCV版本

4.4.0

语言

Python 3.8.5

代码和问题描述：

我试图学习和使用OPENCV，但我遇到了一个奇怪的问题。我不能将网络摄像头与opencv一起使用。Web cam正在使用Cheese应用程序。我尝试了来自this答案的多种解决方案，但都不起作用

我逐行检查代码，发现错误在cv2.VideoCapture(index)

In [1]: import cv2

In [2]: cv2.VideoCapture(0)
[ WARN:0] global /tmp/pip-req-build-a3np7pha/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
Out[2]: <VideoCapture 0x7f1773353550>

In [3]: cv2.VideoCapture(-1)
[ WARN:0] global /tmp/pip-req-build-a3np7pha/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
Out[3]: <VideoCapture 0x7f1773304990>

In [4]: cv2.VideoCapture(1)
[ WARN:0] global /tmp/pip-req-build-a3np7pha/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video1): can't open camera by index
Out[4]: <VideoCapture 0x7f17733048b0>