Everyone on here is going to tell you something different. I'll give you my answer, and that is no it is not. Sparring is the ultimate form of learning self defense. Its the closest thing to simulating a real fight. If you don't spar, your martial art isn't worth jack. Ninjutsu practitioners don't spar, and the reason they say is because its too deadly, that they'd go in there and just kill each other. The real reason is because of the many techniques they teach simply won't work in the ring.
I invite you to watch this video. It'll explain in visuals what I'm trying to show you in words.
http://www.youtube.com/watch?v=orHyWCXO0pw
And as far as learning martial arts through DVD's, its simply not possible. Anyone can mimic the moves you see, but to see it and apply it correctly are two different things. You need someone there to tell you if your doing it right.
Good luck in your travels friend.