opencv cap = cv2.VideoCapture(0) takes a long time to open the webcam please give me a solution

I tried cap = cv2.VideoCapture(1) doesnt work takes a long time too

CodePudding user response：

If you got any kind of warnings, you may need to search for how to fix those warnings.

Or you can try to specify the video source. For example:

# If you are using Windows
cap = cv2.VideoCapture(1, cv2.CAP_DSHOW)

# If you are using Linux
cap = cv2.VideoCapture(1, cv2.CAP_V4L2)

CodePudding user response：

The DSHOW backend API is faster.

On windows:

cap = cv2.VideoCapture(0, cv2.CAP_DSHOW)

CodePudding user response：

This takes 0.9692582 seconds vs 5.8355613;

import cv2
import os

cap = cv2.VideoCapture(0,cv2.CAP_DSHOW)

e1 = cv2.getTickCount()

print(os.name)
# detect operating system 
if os.name != 'nt':
    # Not Windows
    cap = cv2.VideoCapture(1, cv2.CAP_V4L2)

ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
ret, thresh = cv2.threshold(gray, 127, 255, cv2.THRESH_BINARY)
contours, hierarchy = cv2.findContours(
    thresh, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
cv2.drawContours(frame, contours, -1, (0, 255, 0), 3)
e2 = cv2.getTickCount()
time = (e2 - e1) / cv2.getTickFrequency()
print(time)

cv2.imshow('frame', frame)
cv2.waitKey(0)
cap.release()
cv2.destroyAllWindows()

Output: