<s>
A	O
filter	B-Application
driver	I-Application
is	O
a	O
Microsoft	B-Application
Windows	I-Application
driver	O
that	O
extends	O
or	O
modifies	O
the	O
function	O
of	O
peripheral	B-Device
devices	I-Device
or	O
supports	O
a	O
specialized	O
device	O
in	O
the	O
personal	B-Device
computer	I-Device
.	O
</s>
<s>
A	O
filter	B-Application
driver	I-Application
should	O
not	O
affect	O
the	O
normal	O
working	O
of	O
the	O
existing	O
driver	O
stack	O
in	O
any	O
major	O
way	O
.	O
</s>
<s>
Written	O
either	O
by	O
Microsoft	O
or	O
the	O
vendor	O
of	O
the	O
hardware	B-Architecture
,	O
any	O
number	O
of	O
filter	B-Application
drivers	I-Application
can	O
be	O
added	O
to	O
Windows	O
.	O
</s>
<s>
Upper	O
level	O
filter	B-Application
drivers	I-Application
sit	O
above	O
the	O
primary	O
driver	O
for	O
the	O
device	O
(	O
the	O
function	O
driver	O
)	O
,	O
while	O
lower	O
level	O
filter	B-Application
drivers	I-Application
sit	O
below	O
the	O
function	O
driver	O
and	O
above	O
the	O
bus	B-General_Concept
driver	O
.	O
</s>
<s>
Filters	O
may	O
work	O
on	O
a	O
certain	O
brand	O
of	O
device	O
such	O
as	O
a	O
mouse	B-Device
or	O
keyboard	B-Device
,	O
or	O
they	O
may	O
perform	O
some	O
operation	O
on	O
a	O
class	O
of	O
devices	O
,	O
such	O
as	O
any	O
mouse	B-Device
or	O
any	O
keyboard	B-Device
.	O
</s>
<s>
The	O
Windows	O
Dev	O
Center	O
-	O
Hardware	B-Architecture
pages	O
explain	O
upper	O
and	O
lower	O
filter	B-Application
drivers	I-Application
in	O
detail	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
generic	O
USB	O
camera	O
(	O
UVC	O
)	O
driver	O
usbvideo.sys	O
is	O
a	O
function	O
driver	O
,	O
while	O
the	O
bus	B-General_Concept
driver	O
handles	O
USB	O
data	O
from	O
the	O
host	O
controller	O
devices	O
.	O
</s>
<s>
A	O
lower	O
level	O
filter	O
modifies	O
the	O
behavior	O
of	O
the	O
camera	O
hardware	B-Architecture
(	O
e.g.	O
</s>
<s>
watching	O
for	O
interrupt	O
packets	O
from	O
a	O
camera	O
switch	O
)	O
and	O
fits	O
between	O
the	O
function	O
and	O
bus	B-General_Concept
drivers	O
.	O
</s>
<s>
Another	O
type	O
of	O
filter	B-Application
driver	I-Application
is	O
the	O
bus	B-General_Concept
(	O
e.g.	O
</s>
<s>
USB	O
,	O
PCI	O
,	O
PCIe	O
)	O
filter	B-Application
driver	I-Application
,	O
which	O
may	O
be	O
added	O
on	O
top	O
of	O
the	O
bus	B-General_Concept
driver	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
ACPI	B-Device
bus	B-General_Concept
filter	O
is	O
added	O
to	O
support	O
power	O
management	O
for	O
each	O
device	O
.	O
</s>
