python – 如何使用OpenCV从网络摄像头读取视频？

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

while(True):
    # Capture frame-by-frame
    ret,frame = cap.read()

    # Our operations on the frame come here
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)

    # Display the resulting frame
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done,release the capture
cap.release()
cv2.destroyAllWindows()

它失败并带有以下输出：

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor,file /io/opencv/modules/imgproc/src/color.cpp,line 9748
Traceback (most recent call last):
File “capture.py”,line 11,in
gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
cv2.error: /io/opencv/modules/imgproc/src/color.cpp:9748: error: (-215) scn == 3 || scn == 4 in function cvtColor

进一步检查,似乎：

> ret永远是假的.
>添加cap.get(3)(以获得图片的宽度)返回0.0.
>如果我测试cap.isOpened(),结果始终为False.
>如果我添加对cap.open(0)的调用,open也会返回False.
>调用cap.open(“/ dev / video0”)不会改变任何内容.
>用cap = cv2.VideoCapture(“/ dev / video0”)取代cap = cv2.VideoCapture(0)无效.

在VLC中打开/ dev / video0显示来自网络摄像头的视频.当我打开Cheese时,它还会显示来自网络摄像头的视频.只有一台摄像机连接到PC.

有什么建议？