Lag with opencv

First of all, i’d like to say thank you for your previous solving of blue raw.

opencv preview is lagging about 2 seconde on preview i have a lag of about 2s with logitech webcam C920

I try this script in python without lagging:

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

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


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

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

Steps to reproduce the bug

take a photo
preview is late about 2-3 sec
See error.

Is alpha or resizing, can cause this delay? Is it possible to downsample preview to erase latency?

Environment

OS [Raspbian Buster]
Camera [Logitech C920]
Pibooth version [1.1.4]

Thanks

Issue Analytics

State:
Created 4 years ago
Comments:15 (5 by maintainers)

Top GitHub Comments

1reaction

JFK344commented, Feb 8, 2022

In my case the camera was not using the right codec. I used this command to get all the available Codecs.

v4l2-ctl --list-formats-ext

my camera used YUYV which was capable of 6 fps at 1920x1080.

Changed the settings to cam.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter.fourcc('M','J','P','G')) whichs had NO result eighter.

insted of accesssing the camer by index i used reversingCam = cv2.VideoCapture("/dev/video0") which made things working.

heres my whole Code:

import cv2
  
reversingCam = cv2.VideoCapture("/dev/video0")
reversingCam.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter.fourcc('M','J','P','G'))
reversingCam.set(3, 1280)
reversingCam.set(4, 720)

reversingCam.set(cv2.CAP_PROP_BUFFERSIZE, 1)

while(True):
    ret, frame = reversingCam.read()
    
    cv2.imshow('frame', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

reversingCam.release()
cv2.destroyAllWindows()

0reactions

anxuaecommented, May 7, 2021

OpenCV camera improved in pibooth v2.0.2

Please re-open the issue if you are still facing to the same issue.

BR anxuae