Synchronize subtitles of a given movie based on another movie

main.py

import cv2
import numpy
import math
import srt
import datetime
	
vidA = cv2.VideoCapture('movieA.mkv') #reference
vidB = cv2.VideoCapture('movieB.mkv') #to synchronize

with open('subtitles.srt', 'r') as f: #from fileA.mkv
	subs = list(srt.parse(f.read()))

seek = 1000 #adjustment is max [-500;500] frames
midseek = seek//2
posA = 0
posB = 0
permaOffset = 0
queue = []	
	
for s in subs: 
	for offset in [[math.floor(s.start.total_seconds()*25),0], [math.floor(s.end.total_seconds()*25),1]]:

		frameA = offset[0]
		frameB = math.floor(offset[0]*25/24)-540-midseek+permaOffset #assume 25->24 fps conversion
					
		#get reference frame from movieA
		while posA < (frameA+1):
			success,imageA = vidA.read()
			posA = posA + 1

			imageA = cv2.resize(imageA, (720//2, 304//2))
			imageA = cv2.cvtColor(imageA, cv2.COLOR_BGR2GRAY)		
			brightness = numpy.average(imageA)
			imageA = cv2.equalizeHist(imageA)	 		
		
		#fill queue
		while posB < (frameB+seek): 
			success,imageB = vidB.read()
			posB = posB + 1
				
			if posB > frameB:
				imageB = imageB[92:640, 0:1280]	 #crop
				imageB = cv2.resize(imageB, (720//2, 304//2))
				#might do other adjustments as well (eg: zoom)
				#...

				imageB = cv2.cvtColor(imageB, cv2.COLOR_BGR2GRAY)		
				imageB = cv2.equalizeHist(imageB)				
				
				queue.append(imageB)
				if len(queue) > seek:
					queue.pop(0)
				
		#search best matching frame
		best = 0
		max = 0
		bestImage = None

		for x in [-1] + list(range(seek)):
			
			if x==-1:
				earlyExit = True
				x = midseek
			else:
				earlyExit = False
			
			imageB = queue[x]
			
			#try to align both frames before compare
			imageCrop = imageB[50:304-50, 50:720-50] #crop				
			min_val, max_val, min_loc, max_loc = cv2.minMaxLoc(cv2.matchTemplate(imageA, imageCrop, cv2.TM_CCORR_NORMED))
			offsetx = max_loc[0]-50
			offsety = max_loc[1]-50			
			imageB = cv2.warpAffine(imageB, numpy.float32([[1, 0, offsetx],[0, 1, offsety]]), (imageB.shape[1], imageB.shape[0]))
			
			res = cv2.PSNR(imageA, imageB)					
			if res > max: #take best result
				max = res
				best = x 
				bestImage = imageB		
			
			#if frame already get a good score or if brightness is too low, don't bother searching
			if (earlyExit and res > 10.0) or brightness < 40:
				break
				
		#adjust start-end timings 
		target = datetime.timedelta(seconds=(frameB+best)/25)
		if offset[1]==0:
			s.start = target
		else:
			s.end = target
			
		print (s.index, offset, int(max), int(brightness), permaOffset, best-midseek)
				
		permaOffset += best-midseek
		#make sure offset stay in acceptable range
		if permaOffset>400:
			permaOffset = 400
			
		if permaOffset<-400:
			permaOffset = -400

#save subtitles
with open('out.srt', 'w') as f:
	f.write(srt.compose(subs))