Help comparing folders

[aiconan90]

Hi, I am editing videos with ffmpeg and I am trying to automate the process as much as possible. I make a video called frame.mkv to paste other videos (video1,video2,video3.mkv) onto frame.mkv. I need to extract the number of frames from each video to know just exactly how many frames I will need to match the timing on the video so that frame.mkv isn't too long. What I want to do is compare two folders and make sure that the amount of frames from the videos I crop (video1,video2,video3.mkv) will match the number of frames I will need for frame.mkv so, say (video1,video2,video3.mkv) is 300 frames each and I know this because I extracted them to folder A, I would need to make sure that the number of frames in folder B which is for frame.mkv matches exactly 300 frames and deletes the remaining number of frames. A real world example is this, i use a batch file to duplicate the same image for folder B and it wound up being 138,200 images for frame.mkv, meanwhile video.mkv was only 54,225 images. It would be easier for me as an editor to have a script or a program to compare the two folders and automatically delete the uneccesary files. Have any idea what I can do?

Thanks in advance!