python opencv 使用摄像头捕获视频并显示

参考的OpenCV-Python-Toturial-中文版.pdf的代码：

import numpy as np
import cv2

cap = cv2.VideoCapture(0) # 默认内置摄像头

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()
    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BAYER_BG2GRAY)
    # 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()

结果出现下面的错误：

[ WARN:0] videoio(MSMF): OnReadSample() is called with error status: -1072875772
[ WARN:0] videoio(MSMF): async ReadSample() call is failed with error status: -1072875772
[ WARN:1] videoio(MSMF): can't grab frame. Error: -1072875772

解决方案如下：

# import numpy as np 
# import cv2

# camera_number = 0 
# cap = cv2.VideoCapture( camera_number + cv2.CAP_DSHOW)

# # define the codec and create VideoWriter object
# fourcc = cv2.VideoWriter_fourcc(*'XVID')
# out = cv2.VideoWriter('output.avi',fourcc,20.0,(640,480))

# while(cap.isOpened()):
#     ret, frame = cap.read()
#     # write the flipped frame
#     out.write(frame)
#     cv2.imshow('image',frame)
#     if cv2.waitKey(1) & 0xFF == ord('q'):
#         break
#     else:
#         break
        
# # release everything if job is finished
# cap.release()
# out.release()
# cv2.destroyAllWindows()




import numpy as np
import cv2

camera_number = 0 
cap = cv2.VideoCapture( camera_number + cv2.CAP_DSHOW)

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()
    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BAYER_BG2GRAY)
    # 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()

参考的解决方案：
https://stackoverflow.com/questions/51851198/opencv-set-camera-resolution-windows-vrs-linux
https://blog.csdn.net/root__yang/article/details/83180822