Thought of your project when reading the following passage in book on translation:

It has become conventional to regard average moviegoers as capable of reading only about fifteen characters per second; and in order to be legible on a screen as small as a television set, no more than thirty-two alphabetic characters can be displayed in a line. In addition, no more than two lines can be displayed at a time without obscuring significant parts of the image, so the subtitler has around sixty-four characters, including spaces, that can be displayed for a few seconds at most to express the key meanings of a host of sequence in which characters may speak many more words than that. The limits are set by human physiology, average reading speeds, and the physical shape of the movie screen. It’s really amazing that it can be done at all.