I was talking with my friend called Uğur about the project and he was also working on it about the testing part. When we were talking, he gave me such a great idea about configuring the start point of two videos. I was about to do it with showing marker before actually starting to record but that requires a marker which is not practical (OK, it can be simply printed but anyway that is additional work anyway.) so the idea he gave me is "It is possible to determine initial point with sound". So i'll check if i can go with that and if it is easier then marker thing or not.
Well, thanks to Uğur for such a great idea!