There are two types of library research - primary and secondary source.  Secondary source, by far the most common, is reading what someone else wrote about a topic.  Primary source is looking at data of one sort or another.

Secondary source has its limits, and can easily get caught up in the sort of infinite regression loop mentioned earlier.  Primary source research is an entirely different animal.

The fact is complicated by the fact that many disciplines take secondary sources as their primary sources - that is, they look at such writings not for their argument or whatnot, but rather for what the langauge and the nature of the argument made says about the people who did the research and their culture, assumptions, etc.  Anything can be looked at in this fashion, from novels and essays, to diaries, to recpiets and account books, to pages of numeric data left by old scientific studies.

The knowledge produced is, of course, historical, and of thus a different order than any sort of empirical science, and quite likely will have no practical use. However, it's still real research.

One other point, on video.  It's great if there is actually something to be shown to begin with.  When one is dealing with purely abstract notions (philosophy being the best example), video is wasted.  There's just nothing to see in a discussion of the nature of truth.

Again, one might make the argument that, since there's nothing to see, then the field is of questionable value.  But that's another issue entirely.