About Videocapture opencv-CodePudding

OpenCV => 4.2 (4.5.5)
Operating System / Platform => Windows 64 Bit
Compiler => Visual Studio Code
Python Version : 3.8

Hello to everyone,

I want to ask you something about setting height and width set of videocapture.

Is there any fastest way to set the video frame height and width. Because the process, for ex: cap.set(3,720) is too slow. This process takes approximately 6 seconds.

Let me write some code to explain well.

import cv2
import time

cap = cv2.VideoCapture(0)

#Set the resolution

time1 = time.time()
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)
print("time1 is :"   str(time.time() - time1))

time2 = time.time()
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)
print("time2 is :"   str(time.time() - time2))

while(True):
    ret, frame = cap.read()

    # Display the resulting frame
    
    cv2.imshow("preview",frame)
    
    cv2.imwrite("outputImage.jpg", frame)

    #Waits for a user input to quit the application
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

The output is

time1 is : 5.48

time2 is : 5.42

This is too slow to set resolution. I want to reduces this setting time if possible.Is there any faster way to set the resolution do you know?

CodePudding user response：

Pass your desired properties when you instantiate the VideoCapture.

Docs: https://docs.opencv.org/4.x/d8/dfe/classcv_1_1VideoCapture.html#a31e7cf5ba9debaec15437a200b18241e

import cv2 as cv

cap = cv.VideoCapture(index=0, apiPreference=cv.CAP_ANY, params=[
    cv.CAP_PROP_FRAME_WIDTH, 1920,
    cv.CAP_PROP_FRAME_HEIGHT, 1080,
])
assert cap.isOpened()

while True:
    (success, frame) = cap.read()
    if not success: break

    ...

cap.release()

And may I suggest playing with the apiPreference argument? Try CAP_DSHOW as well as CAP_MSMF, since you are on Windows.

CodePudding user response：

Thanks for your answer.

I did what you say but it didn't work. I mean, I tried to pass desired properties when instantiate the VideoCapture but It still takes approximately 20 seconds for initialize.

Also I changed the apiPreference argument, still same.