G-LEC S-Drive II Quick Start Manual - page 9
Understanding Variable Cropping
Due to data rate limitations, the fiber optic link can transmit only something like 400,000 pixels (exact
number depends upon resolution, frequency, and shape). Whereas the S-Drive 1 was merely a converter
and always converted the entire input signal (including 40 trailing blanking lines at the top) to fiber optic
protocol (and thus was limited to 640x480 pixels), the S-Drive II accepts any input resolution, and crops the
needed part and sends it to the panels. The software is written in a manner to make this calculation process
as easy and transparent as possible.
Imagine just one panel you might wish to locate at x = 200, y = 100 (the top-left pixel of the panel shall
show the pixel in row 100, column 200, of your input feed).
With S-Drive 1, the S-Drive wouldn't do any cropping, and wouldn't need to be programmed. The panel
would be programmed to 200 x 140 (remember the aforementioned blanking lines).
With S-Drive II, the S-Drive would be programmed to cropping start at 200 x 100 (automatically allowing for
the blanking lines), and the panel would be programmed to 0 x 0. (Cropping width/height is calculated by
the software too, based on maximum height/width of panels in your setup. S-Drive will default to minimum
cropping dimensions of 150 pixels in smaller setups).
(examples and screenshots are on following pages)
In any case, you do not have to do all the calculations: it's the software which does it for you. All you have
to do is click
Things you should keep in mind:
Unlike with S-Drive 1, some important data – the cropping coordinates - are stored in the S-Drive II.
When using another S-Drive as backup, and expecting immediate switch-over (well, plug-over), make sure
to program both S-Drive II to the same cropping coordinates prior to your show.
Outside the cropping area, no meaningful video signal is being transmitted. Hence, if you forget to
activate 'variable cropping' when uploading, it's likely that your panels are outside the variable cropping
area, and don't show proper content. In that case: activate Variable Cropping, and upload again.
When using S-Drive II, it's common to position frames at y < 40 (see above explanation) – in fact at
least one panel will be at y < 40, since it's the S-Drive who cares for the overall offset. If such a panel is
connected to an S-Drive 1 later, it will be in the blanking area. It will show its serial number, but if not
uploaded correctly, it will flash randomly. Just do a proper upload, and enjoy.
The same is true for x > 640 and y > 480 (520), which might occur in larger setups. Again: make up a
new project, do a proper upload, and off you go.
S-Drive II prior version 1.4 only: if the entire variable cropping area is outside the video input resolution
(e.g. after unintentionally toggling resolution to a smaller one), it's possible that the panels do not show
anything, not even their serial number. The only hint is the message ERR in the S-Drive's display. In that
case, either toggle resolution back to a higher one, or blindly program variable cropping into the resolution
(just make a new project, one panel, no number, switch on variable cropping and upload) – and try again.
S-Drive II version 1.4 and above will temporarily reset to cropping coordinates of 0, 0, 150, 150 in that case
(a 150 px square in the top-left corner of the screen), and panels will at least show their serial number. S-
Drive will show a meaningful message in the display (cropping area outside video area), and the DVI LED
will blink.
The maximum cropping area is approx. 400,000 pixels (width x height). If this is exceeded, distortions
in your content will appear, squares being rectangles etc. Furthermore, there is a max. cropping width of
approx. 1,000 pixels. Full details of this will be given in the full user manual.
G-Lec Vision GmbH
S-Drive II Quick Setup Guide
Page 9