Display Multiple Video in Window Python

Question

I am beginner for the openCV.

I am using below codes to get four video in a file system and show to user. Like this:

V1 | V2
V3 | V4

Video length does not match, If the video comes to end I restart again:

import numpy as np
import cv2



v1 = cv2.VideoCapture('first.avi')
v2 = cv2.VideoCapture('second.avi')
v3 = cv2.VideoCapture('third.avi')
v4 = cv2.VideoCapture('fourth.avi')

v1_length = int(v1.get(cv2.CAP_PROP_FRAME_COUNT))
v2_length = int(v2.get(cv2.CAP_PROP_FRAME_COUNT))
v3_length = int(v3.get(cv2.CAP_PROP_FRAME_COUNT))
v4_length = int(v4.get(cv2.CAP_PROP_FRAME_COUNT))

count1=0
count2 =0
count3= 0
count4 = 0

while True:
    ret1, frame1 = v1.read()
    ret2, frame2 = v2.read()
    ret3, frame3 = v3.read()
    ret4, frame4 = v4.read()
    # print(ret1,ret2,ret3,ret4)

    if count1 == v1_length:
        a = v1.set(cv2.CAP_PROP_POS_FRAMES, 0)

        print(1,count1)
        count1 = 0
    if count2 == v2_length:
        b = v2.set(cv2.CAP_PROP_POS_FRAMES, 0)

        print(2,count2)
        count2 = 0
    if count3 == v3_length:
        c = v3.set(cv2.CAP_PROP_POS_FRAMES, 0)

        print(3,count3)
        count3 = 0
    if count4 == v4_length:
        d = v4.set(cv2.CAP_PROP_POS_FRAMES, 0)

        print(4,count4)
        count4 = 0

    if ret1 and ret2 and ret3 and ret4:
        s1 = np.hstack((frame1,frame2))
        s2 = np.hstack((frame3,frame4))

        s3 = np.vstack((s1,s2))

        cv2.imshow("Result",s3)
        count1 += 1
        count2 += 1
        count3 += 1
        count4 += 1
    else:
        v1 = cv2.VideoCapture('first.avi')
        v2 = cv2.VideoCapture('second.avi')
        v3 = cv2.VideoCapture('third.avi')
        v4 = cv2.VideoCapture('fourth.avi')


    if cv2.waitKey(20) & 0xFF == ord('q'):
        break
v1.release()
v2.release()
v3.release()
v4.release()

cv2.destroyAllWindows() 

It works but I don't think it's a very good code. How can I write better? How can I increase the number of videos more optimized? For example, how can I simply do it when it is 3x3 grid instead of 2x2 video?

Answer 1

The main and the most noticeable problem is code duplication. Imagine you have not 4 but 64 windows.
That's 64 lines every time you need to do something for each video.

Put everything related to particular video instances in a list. When you need to do something for every video, write a for loop.

Instead of

v1 = cv2.VideoCapture('first.avi')
v2 = cv2.VideoCapture('second.avi')
v3 = cv2.VideoCapture('third.avi')
v4 = cv2.VideoCapture('fourth.avi')

you get

for idx in range(len(videos)):
    videos[idx] = cv2.VideoCapture(num2words(idx + 1, to='ordinal') + '.avi')

In this case it's important that you iterate through the indices and change list values at those indices as opposed to iterating through the elements of the list for video in videos: and changing them (it won't actually affect the list).

Then you can group videos by raws based on their index in the list.

After doing that your code will become thin and clean.