Viggo Mortensen pauses a lot when speaking. It’s not that he doesn’t know what to say in answer to a question, it’s that he wants to convey exactly what he means, so he takes the time to choose his words carefully. When asked whether he was worried about comparisons between his work in “Eastern Promises,” which was released on DVD Tuesday, and his role in “A History of Violence” (also made with director David Cronenberg) he says the major difference between his two characters is that in “Eastern Promises,” “my character is quite clear on who he is and what he is attempting to do, what he is sacrificing, what’s at stake. Mortensen oozes intensity