> Hmmm, Interresting. I actully just made a LED panel and I'm having some
> problems. When the picture is moving the dots seems to be double (is this
> what you call "seams"). I fount out that I could remove this by setting
> the
> refresh rate down to once per frame. But then I get flickker due to the
> low
> refresh rate.
> What can I do to prevent this when I change the refresh rate?
> And how these special refresh algorithms working?
> Can the problem be solved by double the display buffer, and how?

I'd suggest that you--either in your imagination or in reality--place a
piece of acetate or other transparent material over the signboard and move
it right to left at the rate the dots will be moving.  Every time a dot
flashes, mark it on the acetate.  [obviously, doing this for real would
require the ability to step through the frames unless you've got a REALLY
fast hand with that Sharpie(r)].

If you do this with a display that's shown twice per, you will observe
that each dot will appear twice on the acetate; the second appearance will
be 1/2 dot to the right of the first.  There is no way to rid yourself of
this phenomenon other than by speeding up the scrolling, slowing down the
refresh, or both so as to be at a rate of one dot per frame.  If neither
of these options is acceptable, you can try instead to take advantage of
the phenomenon by doubling the width of your display buffer and showing
the even pixels on one flash and the odd ones on the other.  This will
allow you to double the perceived resolution of your display, and may help
to reduce the annoying double-dottiness of the scroll.

Additionally, if you are using discrete LED's you may improve the
appearance of *scrolling* text by staggering the LED's in alternate rows.
You then scan the rows in even/odd order, so that the flicker will be less
noticeable than on a straight scan.  Unfortunately, this will be a bit of
an annoying display layout for anything other than text which is scrolling
at the proper speed, but such is life.