I'd like to use a flatbed scanner for continuous capture. By this I mean: 
the scan head does not move, and I regularly (quickly) get updates from
the scan head.

If I understand SANE, there are at least two ways I might do this:

1 Physically modify the scanner to not move the head, and capture images
that are the maximum dimension of the scan area. Use sane_read to
continually update the scan head state, which is accessed by another thread.

2 Capture images that are one pixel tall.

Both of these require using sane_start to get a new frame every so often
(much more often, in the case of 2), and I'm worried about the "glitch"
that will occur at that point. Does anybody have an idea about how long
the scanner will stall while getting ready to start a new frame? It's
probably very scanner-dependent, I'm guessing... but on order of
magnitude guess would be great. Or: is there a way to continue using
sane_read without worrying about approaching an EOF...?

Thanks!
Kyle