-- the output, although you can ignore them if you don't need them
-- (they're useful if you want to e.g. know what to resample by).
--
--- <signals> is basically an exposed InputState, which you can use to
--- query for information about the signals at the point of the current
--- frame. In particular, you can call get_width() and get_height()
--- for any signal number, and use that to e.g. assist in scene selection.
+-- <signals> is an object which you can query for information
+-- about the signals at the point of the current frame. In particular,
+-- you can call get_frame_width() and get_frame_height() for any
+-- signal number, and use that to e.g. see if you wish to enable
+-- a scaler or not. (You can also use get_width() and get_height(),
+-- which return the _field_ size. This has half the height for
+-- interlaced signals.)
--
-- You should return the scene to use, after having set any parameters you
-- want to set (through set_int() etc.). The parameters will be snapshot