Have you looked at the Video Library page

In a private message, you mention the Capture part of the library.
Personally, I only used the MovieMaker class, but saw some uses of the Movie class (in the forum, this huge information pool, as you point out), so I thought that by "video input" you mean reading a movie file.
I was terse because 1) some newcomers just overlook some information, or fail to mention their previous searches, 2) I have no direct experience in the field, but was willing to give a quick answer.

Movie extends PImage, ie. can be treated as such, which is obvious in the available() example, where we have myMovie.read() followed by image(myMovie, 0, 0).

Well, it looks like Capture behaves identically, so I think you have your answer. Which might not been so obvious, on second thought: indeed, stating the above explicitly (instead of letting people guess from code samples) might be good.