<s>
Video4Linux	B-Application
(	O
V4L	B-Application
for	O
short	O
)	O
is	O
a	O
collection	O
of	O
device	B-Application
drivers	I-Application
and	O
an	O
API	B-Application
for	O
supporting	O
realtime	O
video	B-General_Concept
capture	I-General_Concept
on	O
Linux	B-Application
systems	O
.	O
</s>
<s>
It	O
supports	O
many	O
USB	B-Protocol
webcams	B-Protocol
,	O
TV	B-Device
tuners	I-Device
,	O
and	O
related	O
devices	O
,	O
standardizing	O
their	O
output	O
,	O
so	O
programmers	O
can	O
easily	O
add	O
video	O
support	O
to	O
their	O
applications	O
.	O
</s>
<s>
Video4Linux	B-Application
is	O
responsible	O
for	O
creating	O
V4L2	B-Application
device	O
nodes	O
aka	O
a	O
device	O
file	O
(	O
/dev/videoX	O
,	O
/dev/vbiX	O
and	O
/dev/radioX	O
)	O
and	O
tracking	O
data	O
from	O
these	O
nodes	O
.	O
</s>
<s>
The	O
device	O
node	O
creation	O
is	O
handled	O
by	O
V4L	B-Application
device	B-Application
drivers	I-Application
using	O
the	O
video_device	O
struct	O
(	O
v4l2-dev.h	O
)	O
and	O
it	O
can	O
either	O
be	O
allocated	O
dynamically	O
or	O
embedded	O
in	O
another	O
larger	O
struct	O
.	O
</s>
<s>
Video4Linux	B-Application
was	O
named	O
after	O
Video	B-Device
for	I-Device
Windows	I-Device
(	O
which	O
is	O
sometimes	O
abbreviated	O
"	O
V4W	O
"	O
)	O
,	O
but	O
is	O
not	O
technically	O
related	O
to	O
it	O
.	O
</s>
<s>
While	O
Video4Linux	B-Application
is	O
only	O
available	O
on	O
Linux	B-Application
,	O
there	O
is	O
a	O
compatibility	O
layer	O
available	O
for	O
FreeBSD	B-Operating_System
called	O
Video4BSD	O
.	O
</s>
<s>
This	O
provides	O
a	O
way	O
for	O
many	O
programs	O
that	O
depend	O
on	O
V4L	B-Application
to	O
also	O
compile	O
and	O
run	O
on	O
the	O
FreeBSD	B-Operating_System
operating	O
system	O
.	O
</s>
<s>
V4L	B-Application
had	O
been	O
introduced	O
late	O
into	O
the	O
2.1.X	O
development	O
cycle	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
V4L1	O
support	O
was	O
dropped	O
in	O
kernel	B-Operating_System
2.6.38	O
.	O
</s>
<s>
V4L2	B-Application
is	O
the	O
second	O
version	O
of	O
V4L	B-Application
.	O
</s>
<s>
Video4Linux2	O
fixed	O
some	O
design	O
bugs	O
and	O
started	O
appearing	O
in	O
the	O
2.5.x	O
kernels	B-Operating_System
.	O
</s>
<s>
Video4Linux2	O
drivers	O
include	O
a	O
compatibility	O
mode	O
for	O
Video4Linux1	O
applications	O
,	O
though	O
the	O
support	O
can	O
be	O
incomplete	O
and	O
it	O
is	O
recommended	O
to	O
use	O
Video4Linux1	O
devices	O
in	O
V4L2	B-Application
mode	O
.	O
</s>
<s>
The	O
project	O
DVB-Wiki	O
is	O
now	O
hosted	O
on	O
LinuxTV	B-Language
web	O
site	O
.	O
</s>
<s>
Some	O
programs	O
support	O
V4L2	B-Application
through	O
the	O
media	O
resource	O
locator	O
v4l2://	O
.	O
</s>
<s>
Video4Linux	B-Application
has	O
a	O
complex	O
negotiation	O
process	O
,	O
which	O
caused	O
not	O
all	O
applications	O
having	O
support	O
for	O
all	O
cameras	O
.	O
</s>
