<s>
A	O
video	B-Device
wall	I-Device
is	O
a	O
special	O
multi-monitor	B-General_Concept
setup	O
that	O
consists	O
of	O
multiple	O
computer	B-Device
monitors	I-Device
,	O
video	B-Device
projectors	I-Device
,	O
or	O
television	O
sets	O
tiled	O
together	O
contiguously	O
or	O
overlapped	O
in	O
order	O
to	O
form	O
one	O
large	O
screen	O
.	O
</s>
<s>
Typical	O
display	O
technologies	O
include	O
LCD	B-Device
panels	I-Device
,	O
Direct	O
View	O
LED	O
arrays	O
,	O
blended	O
projection	O
screens	O
,	O
Laser	B-Device
Phosphor	I-Device
Displays	I-Device
,	O
and	O
rear	O
projection	O
cubes	O
.	O
</s>
<s>
Jumbotron	B-Application
technology	O
was	O
also	O
previously	O
used	O
.	O
</s>
<s>
Diamond	B-General_Concept
Vision	I-General_Concept
was	O
historically	O
similar	O
to	O
Jumbotron	B-Application
in	O
that	O
they	O
both	O
used	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	O
)	O
technology	O
,	O
but	O
with	O
slight	O
differences	O
between	O
the	O
two	O
.	O
</s>
<s>
Early	O
Diamond	B-General_Concept
vision	I-General_Concept
displays	O
used	O
separate	O
flood	O
gun	O
CRTs	O
,	O
one	O
per	O
subpixel	O
.	O
</s>
<s>
Later	O
Diamond	B-General_Concept
vision	I-General_Concept
displays	O
and	O
all	O
Jumbotrons	B-Application
used	O
field-replaceable	O
modules	O
containing	O
several	O
flood	O
gun	O
CRTs	O
each	O
,	O
one	O
per	O
subpixel	O
,	O
that	O
had	O
common	O
connections	O
shared	O
across	O
all	O
CRTs	O
in	O
a	O
module	O
;	O
the	O
module	O
was	O
connected	O
through	O
a	O
single	O
weather-sealed	O
connector	O
.	O
</s>
<s>
Screens	O
specifically	O
designed	O
for	O
use	O
in	O
video	B-Device
walls	I-Device
usually	O
have	O
narrow	O
bezels	O
in	O
order	O
to	O
minimize	O
the	O
gap	O
between	O
active	O
display	O
areas	O
,	O
and	O
are	O
built	O
with	O
long-term	O
serviceability	O
in	O
mind	O
.	O
</s>
<s>
Such	O
screens	O
often	O
contain	O
the	O
hardware	O
necessary	O
to	O
stack	O
similar	O
screens	O
together	O
,	O
along	O
with	O
connections	O
to	O
daisy	B-Application
chain	I-Application
power	O
,	O
video	O
,	O
and	O
command	O
signals	O
between	O
screens	O
.	O
</s>
<s>
A	O
command	O
signal	O
may	O
,	O
for	O
example	O
,	O
power	O
all	O
screens	O
in	O
the	O
video	B-Device
wall	I-Device
on	O
or	O
off	O
,	O
or	O
calibrate	O
the	O
brightness	O
of	O
a	O
single	O
screen	O
after	O
bulb	O
replacement	O
(	O
in	O
Projection-based	O
screens	O
)	O
.	O
</s>
<s>
Reasons	O
for	O
using	O
a	O
video	B-Device
wall	I-Device
instead	O
of	O
a	O
single	O
large	O
screen	O
can	O
include	O
the	O
ability	O
to	O
customize	O
tile	O
layouts	O
,	O
greater	O
screen	O
area	O
per	O
unit	O
cost	O
,	O
and	O
greater	O
pixel	B-Algorithm
density	I-Algorithm
per	O
unit	O
cost	O
,	O
due	O
to	O
the	O
economics	O
of	O
manufacturing	O
single	O
screens	O
which	O
are	O
unusual	O
in	O
shape	O
,	O
size	O
,	O
or	O
resolution	B-General_Concept
.	O
</s>
<s>
Video	B-Device
walls	I-Device
are	O
sometimes	O
found	O
in	O
control	O
rooms	O
,	O
stadiums	B-Application
,	O
and	O
other	O
large	O
public	O
venues	O
.	O
</s>
<s>
Examples	O
include	O
the	O
video	B-Device
wall	I-Device
in	O
Oakland	O
International	O
Airport	O
's	O
baggage	O
claim	O
,	O
where	O
patrons	O
are	O
expected	O
to	O
observe	O
the	O
display	O
at	O
long	O
distances	O
,	O
and	O
the	O
100	O
screen	O
video	B-Device
wall	I-Device
at	O
McCarran	O
International	O
Airport	O
,	O
which	O
serves	O
as	O
an	O
advertising	O
platform	O
for	O
the	O
40	O
million	O
passengers	O
passing	O
through	O
airport	O
annually	O
.	O
</s>
<s>
Video	B-Device
walls	I-Device
can	O
also	O
benefit	O
smaller	O
venues	O
when	O
patrons	O
may	O
view	O
the	O
screens	O
both	O
up	O
close	O
and	O
at	O
a	O
distance	O
,	O
respectively	O
necessitating	O
both	O
high	O
pixel	B-Algorithm
density	I-Algorithm
and	O
large	O
size	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
100-inch	O
video	B-Device
wall	I-Device
located	O
in	O
the	O
main	O
lobby	O
of	O
the	O
Lafayette	O
Library	O
and	O
Learning	O
Center	O
has	O
enough	O
size	O
for	O
the	O
distant	O
passerby	O
to	O
view	O
photos	O
while	O
also	O
providing	O
the	O
nearby	O
observer	O
enough	O
resolution	B-General_Concept
to	O
read	O
about	O
upcoming	O
events	O
.	O
</s>
<s>
Simple	O
video	B-Device
walls	I-Device
can	O
be	O
driven	O
from	O
multi-monitor	B-General_Concept
video	O
cards	O
,	O
however	O
more	O
complex	O
arrangements	O
may	O
require	O
specialized	O
video	O
processors	O
,	O
specifically	O
designed	O
to	O
manage	O
and	O
drive	O
large	O
video	B-Device
walls	I-Device
.	O
</s>
<s>
Software-based	O
video	B-Device
wall	I-Device
technology	O
that	O
uses	O
ordinary	O
PCs	O
,	O
displays	O
and	O
networking	O
equipment	O
can	O
also	O
be	O
used	O
for	O
video	B-Device
wall	I-Device
deployments	O
.	O
</s>
<s>
The	O
largest	O
video	B-Device
wall	I-Device
as	O
of	O
2013	O
was	O
located	O
at	O
the	O
backstretch	O
of	O
the	O
Charlotte	O
Motor	O
Speedway	O
motorsport	O
track	O
.	O
</s>
<s>
Video	B-Device
walls	I-Device
are	O
not	O
limited	O
to	O
a	O
single	O
purpose	O
but	O
are	O
now	O
being	O
used	O
in	O
dozens	O
of	O
different	O
applications	O
.	O
</s>
<s>
A	O
video	B-Device
wall	I-Device
controller	O
(	O
sometimes	O
called	O
“	O
processor	O
”	O
)	O
is	O
a	O
device	O
that	O
splits	O
a	O
single	O
image	O
into	O
parts	O
to	O
be	O
displayed	O
on	O
individual	O
screens	O
.	O
</s>
<s>
Video	B-Device
wall	I-Device
controllers	O
can	O
be	O
divided	O
into	O
groups	O
:	O
</s>
<s>
The	O
advantage	O
of	O
using	O
a	O
hardware	O
video	B-Device
wall	I-Device
controller	O
is	O
high	O
performance	O
and	O
reliability	O
.	O
</s>
<s>
The	O
most	O
simple	O
example	O
of	O
video	B-Device
wall	I-Device
controller	O
is	O
single	O
input	O
multiple	O
outputs	O
scaler	O
.	O
</s>
<s>
It	O
accepts	O
one	O
video	O
input	O
and	O
splits	O
the	O
image	O
into	O
parts	O
corresponding	O
to	O
displays	O
in	O
the	O
video	B-Device
wall	I-Device
.	O
</s>
<s>
Most	O
of	O
professional	O
video	B-Device
wall	I-Device
displays	O
also	O
have	O
built-in	O
controller	O
(	O
sometimes	O
called	O
an	O
integrated	O
video	O
matrix	O
processor	O
or	O
splitter	O
)	O
.	O
</s>
<s>
This	O
matrix	O
splitter	O
allows	O
to	O
“	O
stretch	O
”	O
the	O
image	O
from	O
a	O
single	O
video	O
input	O
across	O
all	O
the	O
displays	O
within	O
the	O
whole	O
video	B-Device
wall	I-Device
(	O
typically	O
arranged	O
in	O
a	O
linear	O
matrix	O
,	O
e.g.	O
,	O
2x2	O
,	O
4x4	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
It	O
is	O
a	O
fairly	O
simple	O
method	O
to	O
build	O
a	O
video	B-Device
wall	I-Device
but	O
it	O
has	O
some	O
disadvantages	O
.	O
</s>
<s>
First	O
of	O
all	O
,	O
it	O
is	O
impossible	O
to	O
use	O
full	O
pixel	O
resolution	B-General_Concept
of	O
the	O
video	B-Device
wall	I-Device
because	O
the	O
resolution	B-General_Concept
cannot	O
be	O
bigger	O
than	O
the	O
resolution	B-General_Concept
of	O
the	O
input	O
signal	O
.	O
</s>
<s>
These	O
video	B-Device
wall	I-Device
controllers	O
are	O
often	O
built	O
on	O
industrial-grade	O
chassis	O
due	O
to	O
the	O
reliability	O
requirements	O
of	O
control	O
rooms	O
and	O
situational	O
centers	O
.	O
</s>
<s>
Though	O
this	O
approach	O
is	O
typically	O
more	O
expensive	O
,	O
the	O
advantage	O
of	O
a	O
software-based	O
video	B-Device
wall	I-Device
controller	O
vs	O
the	O
hardware	O
splitter	O
is	O
that	O
it	O
can	O
launch	O
applications	O
like	O
maps	O
,	O
VoIP	O
client	O
(	O
to	O
display	O
IP	O
cameras	O
)	O
,	O
SCADA	O
clients	O
,	O
Digital	O
Signage	O
software	O
that	O
can	O
directly	O
utilize	O
the	O
full	O
resolution	B-General_Concept
of	O
the	O
video	B-Device
wall	I-Device
.	O
</s>
<s>
Datapath	O
Limited	O
,	O
Matrox	B-Application
Graphics	I-Application
,	O
Jupiter	O
Systems	O
)	O
.	O
</s>
<s>
Video	B-Device
wall	I-Device
controllers	O
typically	O
support	O
bezel	O
correction	O
(	O
outside	O
frame	O
of	O
monitor	O
)	O
to	O
correct	O
for	O
any	O
bezel	O
with	O
LED	O
displays	O
or	O
overlap	O
the	O
images	O
to	O
blend	O
edges	O
with	O
projectors	O
.	O
</s>
<s>
The	O
integrated	O
video	B-Device
wall	I-Device
scalers	O
are	O
often	O
limited	O
to	O
matrix	O
grid	O
layouts	O
(	O
e.g.	O
,	O
2x2	O
,	O
3x3	O
,	O
4x4	O
,	O
etc	O
.	O
)	O
</s>
<s>
where	O
the	O
aspect	O
ratio	O
of	O
the	O
video	B-Device
wall	I-Device
can	O
be	O
very	O
different	O
from	O
that	O
of	O
individual	O
displays	O
.	O
</s>
<s>
The	O
most	O
advanced	O
video	B-Device
wall	I-Device
controllers	O
enable	O
full	O
artistic	O
control	O
of	O
the	O
displays	O
,	O
enabling	O
a	O
heterogeneous	O
mix	O
of	O
different	O
displays	O
as	O
well	O
as	O
360deg	O
multi-angle	O
rotation	O
of	O
any	O
individual	O
display	O
within	O
the	O
video	B-Device
wall	I-Device
canvas	O
.	O
</s>
<s>
Advanced	O
video	B-Device
wall	I-Device
controllers	O
will	O
allow	O
you	O
to	O
output	O
multiple	O
sources	O
to	O
groups	O
of	O
displays	O
within	O
the	O
video	B-Device
wall	I-Device
and	O
change	O
these	O
zones	O
at	O
will	O
even	O
during	O
live	O
playback	O
.	O
</s>
<s>
The	O
more	O
basic	O
scalers	O
only	O
allow	O
you	O
to	O
output	O
a	O
single	O
source	O
to	O
the	O
entire	O
video	B-Device
wall	I-Device
.	O
</s>
<s>
Some	O
video	B-Device
wall	I-Device
controllers	O
can	O
reside	O
in	O
the	O
server	O
room	O
and	O
communicate	O
with	O
their	O
"	O
graphics	O
cards	O
"	O
over	O
the	O
network	O
.	O
</s>
<s>
Often	O
this	O
is	O
achieved	O
via	O
a	O
traditional	O
video	B-Device
wall	I-Device
controller	O
(	O
with	O
multiple	O
graphics	O
cards	O
)	O
in	O
the	O
server	O
room	O
with	O
a	O
"	O
sender	O
"	O
device	O
attached	O
to	O
each	O
graphics	O
output	O
and	O
a	O
"	O
receiver	O
"	O
attached	O
to	O
each	O
display	O
.	O
</s>
<s>
Even	O
more	O
advanced	O
is	O
a	O
pure	O
network	O
video	B-Device
wall	I-Device
where	O
the	O
server	O
does	O
not	O
require	O
any	O
video	O
cards	O
and	O
communicates	O
directly	O
over	O
the	O
network	O
with	O
the	O
receiver	O
devices	O
.	O
</s>
<s>
Windows-based	O
Network	O
video	B-Device
walls	I-Device
are	O
the	O
most	O
common	O
in	O
the	O
market	O
and	O
will	O
allow	O
a	O
much	O
better	O
functionality	O
.	O
</s>
<s>
A	O
network	O
configuration	O
allows	O
video	B-Device
walls	I-Device
to	O
be	O
synchronized	O
with	O
individual	O
digital	O
signs	O
.	O
</s>
<s>
Transparent	O
video	B-Device
walls	I-Device
combine	O
transparent	O
LCD	B-Device
screens	I-Device
with	O
a	O
video	B-Device
wall	I-Device
controller	O
to	O
display	O
video	O
and	O
still	O
images	O
on	O
a	O
large	O
transparent	O
surface	O
.	O
</s>
<s>
Bezel-less	O
transparent	O
displays	O
can	O
be	O
combined	O
using	O
certain	O
video	B-Device
wall	I-Device
controllers	O
to	O
turn	O
the	O
individual	O
displays	O
into	O
a	O
video	B-Device
wall	I-Device
to	O
cover	O
a	O
significantly	O
larger	O
surface	O
.	O
</s>
<s>
Jason	O
Leigh	O
and	O
others	O
at	O
the	O
Electronic	O
Visualization	O
Laboratory	O
,	O
University	O
of	O
Illinois	O
,	O
Chicago	O
,	O
developed	O
SAGE	O
,	O
the	O
Scalable	O
Adaptive	O
Graphics	O
Environment	O
,	O
allowing	O
the	O
seamless	O
display	O
of	O
various	O
networked	O
applications	O
over	O
a	O
large	O
display	B-Device
wall	I-Device
(	O
LDW	O
)	O
system	O
.	O
</s>
<s>
Different	O
visualization	O
applications	O
such	O
as	O
3D	O
rendering	O
,	O
remote	O
desktop	O
,	O
video	O
streams	O
,	O
and	O
2D	O
maps	O
,	O
stream	O
their	O
rendered	O
pixels	O
to	O
a	O
virtual	O
high-resolution	O
frame	O
buffer	O
on	O
the	O
LDW	O
.	O
</s>
<s>
Chromium	B-Library
is	O
an	O
OpenGL	B-Application
system	O
for	O
interactive	O
rendering	O
on	O
graphics	O
clusters	O
.	O
</s>
<s>
By	O
providing	O
a	O
modified	O
OpenGL	B-Application
library	O
,	O
Chromium	B-Library
can	O
run	O
OpenGL-based	O
applications	O
on	O
a	O
LDW	O
with	O
minimal	O
or	O
no	O
changes	O
.	O
</s>
<s>
One	O
clear	O
advantage	O
of	O
Chromium	B-Library
is	O
utilizing	O
each	O
rendering	O
cluster	O
and	O
achieving	O
high	O
resolution	B-General_Concept
visualization	O
over	O
a	O
LDW	O
.	O
</s>
<s>
Chromium	B-Library
streams	O
OpenGL	B-Application
commands	O
from	O
the	O
`app	O
 '	O
node	O
to	O
other	O
display	O
nodes	O
of	O
a	O
LDW	O
.	O
</s>
<s>
The	O
modified	O
OpenGL	B-Application
library	O
in	O
system	O
handles	O
transferring	O
OpenGL	B-Application
commands	O
to	O
necessary	O
nodes	O
based	O
on	O
their	O
viewport	O
and	O
tile	O
coordinates	O
.	O
</s>
<s>
Since	O
it	O
relies	O
on	O
a	O
relatively	O
small	O
resolution	B-General_Concept
for	O
the	O
display	O
,	O
pixel	O
data	O
can	O
be	O
streamed	O
under	O
the	O
fundamental	O
limit	O
of	O
the	O
network	O
bandwidth	O
.	O
</s>
<s>
The	O
system	O
displays	O
high-resolution	O
still	O
images	O
,	O
HD	O
videos	O
,	O
live	O
HD	O
video	O
streams	O
and	O
PC	O
applications	O
.	O
</s>
