<s>
Professional	B-Protocol
video	I-Protocol
over	I-Protocol
IP	I-Protocol
systems	O
use	O
some	O
existing	O
standard	O
video	B-Application
codec	I-Application
to	O
reduce	O
the	O
program	O
material	O
to	O
a	O
bitstream	O
(	O
e.g.	O
,	O
an	O
MPEG	O
transport	O
stream	O
)	O
,	O
and	O
then	O
to	O
use	O
an	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
network	O
to	O
carry	O
that	O
bitstream	O
encapsulated	B-Protocol
in	O
a	O
stream	O
of	O
IP	O
packets	O
.	O
</s>
<s>
This	O
is	O
typically	O
accomplished	O
using	O
some	O
variant	O
of	O
the	O
RTP	B-Protocol
protocol	O
.	O
</s>
<s>
Carrying	O
professional	B-Protocol
video	I-Protocol
over	I-Protocol
IP	I-Protocol
networks	O
has	O
special	O
challenges	O
compared	O
to	O
most	O
non-time-critical	O
IP	O
traffic	O
.	O
</s>
<s>
Many	O
of	O
these	O
problems	O
are	O
similar	O
to	O
those	O
encountered	O
in	O
voice	B-Application
over	I-Application
IP	I-Application
,	O
but	O
to	O
a	O
much	O
higher	O
level	O
of	O
engineering	O
requirements	O
.	O
</s>
<s>
Since	O
even	O
well-engineered	O
IP	B-Protocol
networks	I-Protocol
tend	O
to	O
have	O
a	O
small	O
residual	O
packet	B-Protocol
loss	I-Protocol
rate	O
caused	O
by	O
low-probability	O
statistical	O
congestion	O
events	O
and	O
amplification	O
of	O
bit	O
errors	O
in	O
the	O
underlying	O
hardware	O
,	O
most	O
professional	O
solutions	O
use	O
some	O
kind	O
of	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
to	O
ensure	O
that	O
the	O
encoded	O
video	O
stream	O
can	O
be	O
reconstructed	O
even	O
if	O
a	O
few	O
packets	O
are	O
lost	O
.	O
</s>
<s>
This	O
is	O
typically	O
applied	O
at	O
the	O
packet	O
level	O
,	O
since	O
the	O
encapsulated	B-Protocol
video	O
bitstream	O
is	O
typically	O
only	O
designed	O
to	O
tolerate	O
low	O
levels	O
of	O
bit	O
or	O
burst	O
errors	O
,	O
rather	O
than	O
the	O
loss	O
of	O
whole	O
packets	O
.	O
</s>
<s>
If	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
is	O
used	O
,	O
a	O
small	O
proportion	O
of	O
packets	O
arriving	O
after	O
the	O
deadline	O
can	O
be	O
tolerated	O
,	O
since	O
they	O
can	O
be	O
dealt	O
with	O
by	O
being	O
discarded	O
on	O
receipt	O
,	O
and	O
then	O
treated	O
in	O
the	O
same	O
way	O
as	O
lost	B-Protocol
packets	I-Protocol
.	O
</s>
<s>
Added	O
time	O
delay	O
is	O
particularly	O
unwelcome	O
in	O
PTZ	B-Algorithm
cameras	I-Algorithm
as	O
it	O
makes	O
operator	O
control	O
difficult	O
at	O
values	O
over	O
250ms	O
.	O
</s>
<s>
Even	O
with	O
packet	B-Protocol
loss	I-Protocol
mitigation	O
,	O
video	O
over	O
IP	O
will	O
only	O
work	O
if	O
the	O
network	O
is	O
capable	O
of	O
carrying	O
the	O
content	O
with	O
some	O
reasonable	O
maximum	O
packet	B-Protocol
loss	I-Protocol
rate	O
.	O
</s>
<s>
See	O
RSVP	B-Protocol
for	O
one	O
approach	O
to	O
IP	B-Protocol
network	I-Protocol
traffic	O
engineering	O
.	O
</s>
<s>
The	O
Pro-MPEG	O
Wide	O
Area	O
Network	O
group	O
has	O
done	O
much	O
recent	O
work	O
on	O
creating	O
a	O
draft	O
standard	O
for	O
interoperable	O
professional	B-Protocol
video	I-Protocol
over	I-Protocol
IP	I-Protocol
.	O
</s>
<s>
Key	O
components	O
of	O
IP-based	O
CCTV	O
remain	O
consistent	O
with	O
analog	O
technologies	O
:	O
image	O
capture	O
,	O
with	O
a	O
combination	O
of	O
IP-based	O
cameras	O
or	O
analog	O
cameras	O
using	O
IP-based	O
encoders	O
;	O
image	O
transmission	O
;	O
Storage	O
and	O
Retrieval	O
,	O
which	O
uses	O
technologies	O
such	O
as	O
RAID	B-Architecture
arrays	I-Architecture
and	O
iSCSI	B-Protocol
for	O
recorded	O
and	O
indexed	O
video	O
;	O
and	O
video	O
management	O
,	O
which	O
affords	O
web	O
browser-enabled	O
management	O
and	O
control	O
of	O
IP-based	O
CCTV	O
systems	O
.	O
</s>
<s>
Manufacturers	O
of	O
CCTV	O
equipment	O
are	O
steadily	O
integrating	O
IP	B-Protocol
network	I-Protocol
technology	O
into	O
their	O
product	O
portfolios	O
.	O
</s>
