<s>
The	O
zap	B-Device
time	I-Device
is	O
the	O
total	O
duration	O
of	O
time	O
from	O
which	O
the	O
viewer	O
changes	O
the	O
channel	O
using	O
a	O
remote	B-Protocol
control	I-Protocol
to	O
the	O
point	O
that	O
the	O
picture	O
of	O
the	O
new	O
channel	O
is	O
displayed	O
.	O
</s>
<s>
These	O
delays	O
exist	O
in	O
all	O
television	O
systems	O
,	O
but	O
they	O
are	O
more	O
pronounced	O
in	O
digital	B-Application
television	I-Application
and	O
systems	O
that	O
use	O
the	O
internet	O
such	O
as	O
IPTV	O
.	O
</s>
<s>
Human	O
interaction	O
with	O
the	O
system	O
is	O
completely	O
ignored	O
in	O
these	O
measurements	O
,	O
so	O
zap	B-Device
time	I-Device
is	O
not	O
the	O
same	O
as	O
channel	O
surfing	O
.	O
</s>
<s>
Zap	B-Device
time	I-Device
can	O
be	O
very	O
disturbing	O
for	O
some	O
viewers	O
and	O
for	O
this	O
reason	O
it	O
is	O
considered	O
an	O
issue	O
that	O
must	O
be	O
addressed	O
in	O
IPTV	O
systems	O
.	O
</s>
<s>
IGMP	B-Protocol
features	O
used	O
(	O
version	O
,	O
fast	O
leave	O
,	O
snooping	O
,	O
etc	O
.	O
)	O
</s>
<s>
Core/aggregation	B-General_Concept
network	I-General_Concept
latency	O
:	O
</s>
<s>
Network	O
factors	O
tend	O
to	O
make	O
up	O
only	O
a	O
small	O
portion	O
of	O
the	O
overall	O
delay	O
,	O
between	O
50	O
and	O
200ms	O
of	O
the	O
overall	O
zap	B-Device
time	I-Device
.	O
</s>
<s>
Typical	O
frequency	O
of	O
I-frame	B-General_Concept
–	O
500ms	O
.	O
</s>
<s>
The	O
various	O
factors	O
that	O
affect	O
zap	B-Device
time	I-Device
do	O
not	O
do	O
so	O
in	O
the	O
same	O
way	O
.	O
</s>
<s>
The	O
table	O
below	O
is	O
an	O
example	O
of	O
zap	B-Device
time	I-Device
in	O
IPTV	O
DSL	O
:	O
</s>
<s>
Zap	B-Device
time	I-Device
delays	O
are	O
greater	O
in	O
IPTV	O
television	O
than	O
in	O
other	O
technologies	O
.	O
</s>
