This little java application adds dictionary definitions to video subtitle files, with the interface in the video itself. For Japanese text online we have extensions like Rikai that let us look up words as we read, but there hasn't been anything for videos until now. At least not one that can be used on any device.
Jijimaku is a video overlay that shows Japanese definitions on screen, just long enough for you to pause the video, check the meaning, and continue. It isn't meant to be a subtitle program, but rather a quick reference so that you don't have to stop what you're doing and look up a new word. One of its biggest draws is that it claims to work for "any O.S., on smartphone, on TV, etc…"
You also have the option to either ignore words by frequency or ignore a list of words that you enter yourself. If you watch a lot of video content to study, this could be a huge time saver for your current routine.