<s>
H.320	B-Application
or	O
Narrow-band	O
visual	B-Application
telephone	I-Application
systems	O
and	O
terminal	O
equipment	O
is	O
an	O
umbrella	O
Recommendation	O
by	O
the	O
ITU-T	O
for	O
running	O
Multimedia	O
(	O
Audio/Video/Data	O
)	O
over	O
ISDN	B-Protocol
based	O
networks	O
.	O
</s>
<s>
The	O
main	O
protocols	O
in	O
this	O
suite	O
are	O
H.221	O
,	O
H.230	O
,	O
H.242	O
,	O
audio	B-Algorithm
codecs	I-Algorithm
such	O
as	O
G.711	B-Algorithm
(	O
PCM	B-Algorithm
)	O
and	O
G.728	B-Algorithm
(	O
CELP	B-Algorithm
)	O
,	O
and	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
video	B-Application
codecs	I-Application
such	O
as	O
H.261	B-Algorithm
and	O
H.263	B-Algorithm
.	O
</s>
<s>
It	O
is	O
formally	O
named	O
as	O
Narrow-band	O
visual	B-Application
telephone	I-Application
systems	O
and	O
terminal	O
equipment	O
.	O
</s>
<s>
It	O
specifies	O
technical	O
requirements	O
for	O
narrow-band	O
visual	B-Application
telephone	I-Application
systems	O
and	O
terminal	O
equipment	O
,	O
typically	O
for	O
videoconferencing	B-Application
and	O
videophone	B-Application
services	O
.	O
</s>
<s>
The	O
service	O
requirements	O
for	O
visual	B-Application
telephone	I-Application
services	O
are	O
presented	O
in	O
ITU-T	O
Recs	O
F.720	O
for	O
videotelephony	B-Application
and	O
F.702	O
for	O
videoconference	B-Application
.	O
</s>
<s>
This	O
channel	O
capacity	O
may	O
be	O
provided	O
as	O
a	O
single	O
B/H0/H11/H12	O
-channel	O
or	O
multiple	O
B/H0	O
-channels	O
in	O
ISDN	B-Protocol
.	O
</s>
<s>
Used	O
video	B-Application
codecs	I-Application
:	O
H.261	B-Algorithm
,	O
and	O
optionally	O
H.262	B-Algorithm
,	O
H.263	B-Algorithm
,	O
H.264	B-Application
according	O
to	O
the	O
video	O
hierarchy	O
specified	O
in	O
specification	O
,	O
and	O
in	O
ITU-T	O
Recs	O
H.241	O
and	O
H.242	O
.	O
</s>
<s>
H.261	B-Algorithm
is	O
mandatory	O
in	O
any	O
enhanced	O
H.320	B-Application
system	O
with	O
video	O
capability	O
.	O
</s>
<s>
Baseline	O
H.263	B-Algorithm
capability	O
shall	O
be	O
required	O
in	O
systems	O
that	O
use	O
enhanced	O
video	O
modes	O
.	O
</s>
<s>
Used	O
audio	B-Algorithm
codecs	I-Algorithm
:	O
G.711	B-Algorithm
,	O
and	O
optionally	O
G.722	B-Algorithm
,	O
G.728	B-Algorithm
,	O
G.723.1	B-Algorithm
,	O
G.729	B-Algorithm
.	O
</s>
<s>
(	O
Example	O
of	O
usage	O
:	O
If	O
a	O
visual	B-Application
telephone	I-Application
interworks	O
with	O
a	O
wideband	O
speech	O
terminal	O
,	O
G.722	B-Algorithm
audio	O
may	O
be	O
used	O
instead	O
of	O
G.711	B-Algorithm
audio	O
.	O
)	O
</s>
