Unable to limit frames per second while reading frames python

Question

I have the following code in which I am reading data from folder, I want to limit the number of frame rate to 5fps, 10fps,15fps,20fps,25fps being read from a folder. When I run below code my code is hanged and I doubt the below approach I am using is not correct.

filenames = [img for img in glob.glob("video-frames/*.jpg")]
fps = 5
#calculate the interval between frame.
interval = int(1000/fps)
filenames = sorted(filenames, key=os.path.getctime) or filenames.sort(key=os.path.getctime)
images = []
for img in filenames:
  n= cv2.imread(img)
  time.sleep(interval)
  images.append(n)
  print(img)

Help is highly appreciated if someone would help me in this regard.

If you sleep for 200 seconds (1000/5) it will appear hung. – Mark Setchell Dec 10 '20 at 18:24 — Mark Setchell, Dec 10 '20 at 18:24

score 1 · Accepted Answer · answered Dec 11 '20 at 15:20

I think you can use this relation for calculating the intervals:

delay = int((1 / int(fps)) * 1000)

Here I rewrote your code with the above formula. Also, I added cv2.imshow() for showing images and cv2.waitKey for making the delay.

import cv2
import os
import glob

file_names = [img for img in glob.glob("video-frames/*.jpg")]
fps = 5

# calculate the interval between frames.
delay = int((1 / int(fps)) * 1000)

file_names = sorted(file_names, key=os.path.getctime) or file_names.sort(key=os.path.getctime)
images = []

# Creating a window for showing the images
cv2.namedWindow('images', cv2.WINDOW_NORMAL)

for path in file_names:
    image = cv2.imread(path)

    # time.sleep(interval)
    
    cv2.waitKey(delay)
    # Show an image
    cv2.imshow('images', image)

    images.append(image)
    print(path)

Thanks, @MohammadHosseinZiyaaddini, would you please let me know why you are multiplying it with 1000? — gohar shah, Dec 11 '20 at 17:15
@goharshah YW. Please follow this [thread](https://stackoverflow.com/questions/25182278/opencv-python-video-playback-how-to-set-the-right-delay-for-cv2-waitkey). — MohammadHosseinZiyaaddini, Dec 12 '20 at 05:49

Unable to limit frames per second while reading frames python

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