<s>
Internet	B-Algorithm
Low	I-Algorithm
Bitrate	I-Algorithm
Codec	I-Algorithm
(	O
iLBC	B-Algorithm
)	O
is	O
a	O
royalty-free	O
narrowband	O
speech	O
audio	O
coding	O
format	O
and	O
an	O
open-source	B-Application
reference	O
implementation	O
(	O
codec	B-General_Concept
)	O
,	O
developed	O
by	O
Global	B-Application
IP	I-Application
Solutions	I-Application
(	O
GIPS	O
)	O
formerly	O
Global	O
IP	O
Sound	O
(	O
acquired	O
by	O
Google	B-Application
Inc	I-Application
in	O
2011	O
)	O
.	O
</s>
<s>
It	O
was	O
formerly	O
freeware	B-License
with	O
limitations	O
on	O
commercial	O
use	O
,	O
but	O
since	O
2011	O
it	O
is	O
available	O
under	O
a	O
free	O
software/open	O
source	O
(	O
3-clause	B-Operating_System
BSD	I-Operating_System
license	O
)	O
license	O
as	O
a	O
part	O
of	O
the	O
open	O
source	O
WebRTC	B-Protocol
project	O
.	O
</s>
<s>
It	O
is	O
suitable	O
for	O
VoIP	B-Application
applications	O
,	O
streaming	O
audio	O
,	O
archival	O
and	O
messaging	O
.	O
</s>
<s>
The	O
algorithm	O
is	O
a	O
version	O
of	O
block-independent	O
linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
,	O
with	O
the	O
choice	O
of	O
data	B-Protocol
frame	I-Protocol
lengths	O
of	O
20	O
and	O
30	O
milliseconds	O
.	O
</s>
<s>
The	O
encoded	O
blocks	O
have	O
to	O
be	O
encapsulated	O
in	O
a	O
suitable	O
protocol	O
for	O
transport	O
,	O
usually	O
the	O
Real-time	B-Protocol
Transport	I-Protocol
Protocol	I-Protocol
(	O
RTP	O
)	O
.	O
</s>
<s>
iLBC	B-Algorithm
handles	O
lost	O
frames	O
through	O
graceful	O
speech	O
quality	O
degradation	O
.	O
</s>
<s>
Ordinary	O
low-bitrate	O
codecs	B-General_Concept
exploit	O
dependencies	O
between	O
speech	O
frames	O
,	O
which	O
cause	O
errors	O
to	O
propagate	O
when	O
packets	O
are	O
lost	O
or	O
delayed	O
.	O
</s>
<s>
In	O
contrast	O
,	O
iLBC-encoded	O
speech	O
frames	O
are	O
independent	O
and	O
so	O
this	O
problem	O
will	O
not	O
occur	O
.	O
</s>
<s>
iLBC	B-Algorithm
is	O
defined	O
in	O
RFC	O
3951	O
.	O
</s>
<s>
It	O
is	O
one	O
of	O
the	O
codecs	B-General_Concept
used	O
by	O
Gizmo5	B-Application
,	O
WebRTC	B-Protocol
,	O
Ekiga	B-Language
,	O
Google	B-Application
Talk	I-Application
,	O
Maemo	O
Recorder	O
(	O
on	O
the	O
Nokia	O
N800/N810	O
)	O
,	O
Polycom	O
IP	O
Phone	O
,	O
Cisco	O
,	O
QuteCom	B-Protocol
,	O
Tuenti	O
,	O
Yahoo	B-Application
!	O
</s>
<s>
iLBC	B-Algorithm
was	O
submitted	O
to	O
IETF	O
in	O
2002	O
and	O
the	O
final	O
specification	O
was	O
published	O
in	O
2004	O
.	O
</s>
<s>
Since	O
2011	O
it	O
is	O
available	O
under	O
an	O
open	O
source	O
(	O
3-clause	B-Operating_System
BSD	I-Operating_System
license	O
)	O
license	O
as	O
a	O
part	O
of	O
the	O
open	O
source	O
WebRTC	B-Protocol
project	O
.	O
</s>
