You are right that you need to input the particular video for now, but we are expanding to include multi-video search (constantly indexing in the background). Right now the use case is particularly nice for finding phrases in long videos (look for Donald Trump saying random stuff {wall, tremendous, many many, women}, it is pretty comical - e.g. http://www.lexika.io/?s=https%3A%2F%2Fwww.youtube.com%2Fwatc...).