<s>
P2PTV	B-Operating_System
refers	O
to	O
peer-to-peer	O
(	O
P2P	O
)	O
software	O
applications	O
designed	O
to	O
redistribute	O
video	O
streams	O
in	O
real	O
time	O
on	O
a	O
P2P	O
network	O
;	O
the	O
distributed	O
video	O
streams	O
are	O
typically	O
TV	B-Operating_System
channels	O
from	O
all	O
over	O
the	O
world	O
but	O
may	O
also	O
come	O
from	O
other	O
sources	O
.	O
</s>
<s>
The	O
draw	O
to	O
these	O
applications	O
is	O
significant	O
because	O
they	O
have	O
the	O
potential	O
to	O
make	O
any	O
TV	B-Operating_System
channel	O
globally	O
available	O
by	O
any	O
individual	O
feeding	O
the	O
stream	O
into	O
the	O
network	O
where	O
each	O
peer	O
joining	O
to	O
watch	O
the	O
video	O
is	O
a	O
relay	O
to	O
other	O
peer	O
viewers	O
,	O
allowing	O
a	O
scalable	O
distribution	O
among	O
a	O
large	O
audience	O
with	O
no	O
incremental	O
cost	O
for	O
the	O
source	O
.	O
</s>
<s>
In	O
a	O
P2PTV	B-Operating_System
system	O
,	O
each	O
user	O
,	O
while	O
downloading	O
a	O
video	O
stream	O
,	O
is	O
simultaneously	O
also	O
uploading	O
that	O
stream	O
to	O
other	O
users	O
,	O
thus	O
contributing	O
to	O
the	O
overall	O
available	O
bandwidth	O
.	O
</s>
<s>
The	O
architecture	O
of	O
many	O
P2PTV	B-Operating_System
networks	O
can	O
be	O
thought	O
of	O
as	O
real-time	O
versions	O
of	O
BitTorrent	B-Protocol
:	O
if	O
a	O
user	O
wishes	O
to	O
view	O
a	O
certain	O
channel	O
,	O
the	O
P2PTV	B-Operating_System
software	O
contacts	O
a	O
"	O
tracker	O
server	O
"	O
for	O
that	O
channel	O
in	O
order	O
to	O
obtain	O
addresses	O
of	O
peers	O
who	O
distribute	O
that	O
channel	O
;	O
it	O
then	O
contacts	O
these	O
peers	O
to	O
receive	O
the	O
feed	O
.	O
</s>
<s>
In	O
effect	O
,	O
this	O
creates	O
an	O
overlay	B-Architecture
network	I-Architecture
on	O
top	O
of	O
the	O
regular	O
internet	O
for	O
the	O
distribution	O
of	O
real-time	O
video	O
content	O
.	O
</s>
<s>
The	O
need	O
for	O
a	O
tracker	O
can	O
also	O
be	O
eliminated	O
by	O
the	O
use	O
of	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
technology	O
.	O
</s>
<s>
Some	O
applications	O
allow	O
users	O
to	O
broadcast	O
their	O
own	O
streams	O
,	O
whether	O
self-produced	O
,	O
obtained	O
from	O
a	O
video	O
file	O
,	O
or	O
through	O
a	O
TV	B-Device
tuner	I-Device
card	I-Device
or	O
video	O
capture	O
card	O
.	O
</s>
<s>
Many	O
of	O
the	O
commercial	O
P2PTV	B-Operating_System
applications	O
were	O
developed	O
in	O
China	O
(	O
TVUPlayer	O
,	O
PPLive	O
,	O
QQLive	O
,	O
PPStream	B-Language
)	O
.	O
</s>
<s>
The	O
majority	O
of	O
available	O
applications	O
broadcast	O
mainly	O
Asian	O
TV	B-Operating_System
stations	O
,	O
with	O
the	O
exception	O
of	O
TVUPlayer	O
,	O
which	O
carries	O
a	O
number	O
of	O
North	O
American	O
stations	O
including	O
CBS	O
,	O
Spike	O
TV	B-Operating_System
,	O
and	O
Fox	O
News	O
.	O
</s>
<s>
Some	O
applications	O
distribute	O
TV	B-Operating_System
channels	O
without	O
a	O
legal	O
license	O
to	O
do	O
so	O
;	O
this	O
utilization	O
of	O
P2P	O
technology	O
is	O
particularly	O
popular	O
to	O
view	O
channels	O
that	O
are	O
either	O
not	O
available	O
locally	O
,	O
or	O
only	O
available	O
by	O
paid	O
subscription	O
,	O
as	O
is	O
the	O
case	O
for	O
some	O
sports	O
channels	O
.	O
</s>
<s>
Distributing	O
links	O
to	O
pirated	O
P2PTV	B-Operating_System
feeds	O
on	O
a	O
U.S.-based	O
Web	O
site	O
can	O
result	O
in	O
the	O
U.S.	O
government	O
seizing	O
the	O
Web	O
site	O
,	O
as	O
it	O
did	O
with	O
several	O
P2PTV	B-Operating_System
aggregation	O
sites	O
prior	O
to	O
Super	O
Bowl	O
XLV	O
.	O
</s>
<s>
By	O
January	O
2009	O
,	O
there	O
were	O
about	O
14,000	O
P2P	O
channels	O
on	O
PPStream	B-Language
.	O
</s>
<s>
Other	O
commercial	O
P2PTV	B-Operating_System
applications	O
outside	O
China	O
are	O
Abroadcasting	O
(	O
USA	O
)	O
,	O
Zattoo	O
(	O
Switzerland/USA	O
)	O
,	O
Octoshape	O
(	O
Denmark	O
)	O
,	O
LiveStation	O
(	O
UK	O
)	O
.	O
</s>
<s>
Broadcasting	O
via	O
a	O
P2PTV	B-Operating_System
system	O
is	O
usually	O
much	O
cheaper	O
than	O
the	O
alternatives	O
and	O
can	O
be	O
done	O
by	O
private	O
individuals	O
.	O
</s>
<s>
Compared	O
to	O
unicasting	B-Protocol
(	O
the	O
standard	O
server-client	O
architecture	O
used	O
in	O
streaming	O
media	O
)	O
no	O
one	O
can	O
guarantee	O
a	O
reliable	O
stream	O
,	O
since	O
every	O
user	O
is	O
a	O
rebroadcaster	O
.	O
</s>
<s>
An	O
example	O
is	O
Akamai	B-Application
.	O
</s>
<s>
App	O
Fully	O
Distributed	O
Public	O
Private	O
FOSS	B-License
First	O
Release	O
Windows	O
Linux	O
Mac	O
Android	O
iOS	O
CommentsAce	O
Stream	O
?	O
</s>
<s>
home	O
source	O
Tribler	B-Language
?	O
</s>
