Use VapourSynth to extract video frames for comparision

make_comparision.py

import vapoursynth as vs
import random
from os import mkdir
from os.path import exists, basename, dirname, splitext
import numpy as np
import cv2 as cv
import mvsfunc as mvs

core = vs.get_core()
encodeddir = r''
#copy as much as you need
bdmvdirs = [
	r''
]
compare_vids_group = [
	[
		#This order is not hard requirement
		bdmvdirs[0] + '',
		encodeddir + '',
	],
]

comppicdir = encodeddir + 'com/'
if not exists(comppicdir): mkdir(comppicdir)

for group in compare_vids_group:
	print('Reading ' + group[0])
	src_o = core.lsmas.LWLibavSource(group[0])
	print('Reading ' + group[1])
	src_e1 = core.lsmas.LWLibavSource(group[1])
	#print('Reading ' + group[2])
	#src_e2 = core.lsmas.LWLibavSource(group[2])
	
	epdir = comppicdir + '{ep}/'.format(ep=splitext(basename(group[2]))[0])
	if not exists(epdir): mkdir(epdir)
	
	total_frames = src_o.num_frames
	frames = []
	#Randomly insert or just fill the list above
	for i in range(10): frames.append(random.randint(0, total_frames))
	frames.sort()
	
	for fr in frames:
		clips = [
			src_o[fr],
			src_e1[fr],
			#src_e2[fr]
		]
		for cl in clips:
			#10 bit source with depth=8 will make cv.merge() give you picture with only darkness
			rgbcl = mvs.ToRGB(input=cl, depth=16, kernel='spline64')
			rgbcl = rgbcl.get_frame(0)
			#final path to output image file:
				#%ep% derived your encoded filename
				#%frame% self explaintory
				#%source% where this frame come from
				#%encodeddir%/com/%ep%/%frame%-%source%.png
			fntmpl = epdir + '{fr}-{srcf}.png'
			srcbase = basename(group[clips.index(cl)])
			nbase = splitext(srcbase)[0]
			nfn = fntmpl.format(srcf=nbase, fr=fr)
			print('Saving frame {n} of {src} to {fn}'.format(n=fr, src=srcbase, fn=nfn))
			planes_count = rgbcl.format.num_planes
			v = cv.merge([np.array(rgbcl.get_read_array(i), copy=False) for i in reversed(range(planes_count))])
			cv.imwrite(nfn, v)

Get OpenCV and NumPy here for easy install
mvsfunc