<s>
G.729	B-Algorithm
is	O
a	O
royalty-free	O
narrow-band	O
vocoder-based	O
audio	O
data	O
compression	O
algorithm	O
using	O
a	O
frame	O
length	O
of	O
10	O
milliseconds	O
.	O
</s>
<s>
It	O
is	O
officially	O
described	O
as	O
Coding	O
of	O
speech	O
at	O
8	O
kbit/s	O
using	O
code-excited	B-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
speech	B-Application
coding	I-Application
(	O
CS-ACELP	B-Algorithm
)	O
,	O
and	O
was	O
introduced	O
in	O
1996	O
.	O
</s>
<s>
The	O
wide-band	O
extension	O
of	O
G.729	B-Algorithm
is	O
called	O
G.729.1	B-Algorithm
,	O
which	O
equals	O
G.729	B-Algorithm
Annex	O
J	O
.	O
</s>
<s>
Because	O
of	O
its	O
low	O
bandwidth	O
requirements	O
,	O
G.729	B-Algorithm
is	O
mostly	O
used	O
in	O
voice	B-Application
over	I-Application
Internet	I-Application
Protocol	I-Application
(	O
VoIP	B-Application
)	O
applications	O
when	O
bandwidth	O
must	O
be	O
conserved	O
.	O
</s>
<s>
Standard	O
G.729	B-Algorithm
operates	O
at	O
a	O
bit	O
rate	O
of	O
8	O
kbit/s	O
,	O
but	O
extensions	O
provide	O
rates	O
of	O
6.4	O
kbit/s	O
(	O
Annex	O
D	O
,	O
F	O
,	O
H	O
,	O
I	O
,	O
C+	O
)	O
and	O
11.8	O
kbit/s	O
(	O
Annex	O
E	O
,	O
G	O
,	O
H	O
,	O
I	O
,	O
C+	O
)	O
for	O
worse	O
and	O
better	O
speech	O
quality	O
,	O
respectively	O
.	O
</s>
<s>
G.729	B-Algorithm
has	O
been	O
extended	O
with	O
various	O
features	O
,	O
commonly	O
designated	O
as	O
G.729a	B-Algorithm
and	O
G.729b	O
:	O
</s>
<s>
G.729	B-Algorithm
:	O
This	O
is	O
the	O
original	O
codec	B-General_Concept
using	O
a	O
high-complexity	O
algorithm	O
.	O
</s>
<s>
G.729A	B-Algorithm
or	O
Annex	O
A	O
:	O
This	O
version	O
has	O
a	O
medium	O
complexity	O
,	O
and	O
is	O
compatible	O
with	O
G.729	B-Algorithm
.	O
</s>
<s>
G.729B	O
or	O
Annex	O
B	O
:	O
This	O
version	O
extends	O
G.729	B-Algorithm
with	O
silence	O
suppression	O
,	O
and	O
is	O
not	O
compatible	O
with	O
the	O
previous	O
versions	O
.	O
</s>
<s>
G.729AB	B-Algorithm
:	O
This	O
version	O
extends	O
G.729A	B-Algorithm
with	O
silence	O
suppression	O
,	O
and	O
is	O
only	O
compatible	O
with	O
G.729B	O
.	O
</s>
<s>
G.729.1	B-Algorithm
or	O
Annex	O
J	O
:	O
This	O
version	O
extends	O
G.729A	B-Algorithm
and	O
B	O
with	O
scalable	O
variable	O
encoding	O
using	O
hierarchical	O
enhancement	O
layers	O
.	O
</s>
<s>
Dual-tone	O
multi-frequency	O
signaling	O
(	O
DTMF	O
)	O
,	O
fax	O
transmissions	O
,	O
and	O
high-quality	O
audio	O
cannot	O
be	O
transported	O
reliably	O
with	O
this	O
codec	B-General_Concept
.	O
</s>
<s>
DTMF	O
requires	O
the	O
use	O
of	O
the	O
named	O
telephony	O
events	O
in	O
the	O
RTP	B-Protocol
payload	O
for	O
DTMF	O
digits	O
,	O
telephony	O
tones	O
,	O
and	O
telephony	O
signals	O
as	O
specified	O
in	O
RFC	O
4733	O
.	O
</s>
<s>
G.729a	B-Algorithm
is	O
a	O
compatible	O
extension	O
of	O
G.729	B-Algorithm
,	O
but	O
requires	O
less	O
computational	O
power	O
.	O
</s>
<s>
G.729a	B-Algorithm
was	O
developed	O
by	O
a	O
consortium	O
of	O
organizations	O
:	O
France	O
Télécom	O
,	O
Mitsubishi	O
Electric	O
Corporation	O
,	O
Nippon	O
Telegraph	O
and	O
Telephone	O
Corporation	O
(	O
NTT	O
)	O
.	O
</s>
<s>
The	O
features	O
of	O
G.729a	B-Algorithm
are	O
:	O
</s>
<s>
The	O
complexity	O
of	O
the	O
algorithm	O
is	O
rated	O
at	O
15	O
,	O
using	O
a	O
relative	O
scale	O
where	O
G.711	B-Algorithm
is	O
1	O
and	O
G.723.1	B-Algorithm
is	O
25	O
.	O
</s>
<s>
Some	O
VoIP	B-Application
phones	O
incorrectly	O
use	O
the	O
description	O
"	O
G729a/8000	O
"	O
in	O
SDP	B-Language
(	O
e.g.	O
</s>
<s>
This	O
is	O
incorrect	O
as	O
G729a	O
is	O
an	O
alternative	O
method	O
of	O
encoding	O
the	O
audio	O
,	O
but	O
still	O
generates	O
data	O
decodable	O
by	O
either	O
G729	B-Algorithm
or	O
G729a	O
-	O
i.e.	O
</s>
<s>
there	O
is	O
no	O
difference	O
in	O
terms	O
of	O
codec	B-General_Concept
negotiation	O
.	O
</s>
<s>
Since	O
the	O
SDP	B-Language
RFC	O
allows	O
static	O
payload	O
types	O
to	O
be	O
overridden	O
by	O
the	O
textual	O
rtpmap	O
description	O
this	O
can	O
cause	O
problems	O
calling	O
from	O
these	O
phones	O
to	O
endpoints	O
adhering	O
to	O
the	O
RFC	O
unless	O
the	O
codec	B-General_Concept
is	O
renamed	O
in	O
their	O
settings	O
since	O
they	O
will	O
not	O
recognise	O
'	O
G729a	O
 '	O
as	O
'	O
G729	B-Algorithm
 '	O
without	O
a	O
specific	O
workaround	O
in	O
place	O
for	O
the	O
bug	O
.	O
</s>
<s>
G.729	B-Algorithm
has	O
been	O
extended	O
in	O
Annex	O
B	O
(	O
G.729b	O
)	O
which	O
provides	O
a	O
silence	O
compression	O
method	O
that	O
enables	O
a	O
voice	B-General_Concept
activity	I-General_Concept
detection	I-General_Concept
(	O
VAD	O
)	O
module	O
.	O
</s>
<s>
It	O
also	O
includes	O
a	O
discontinuous	O
transmission	O
(	O
DTX	O
)	O
module	O
which	O
decides	O
on	O
updating	O
the	O
background	O
noise	O
parameters	O
for	O
non	O
speech	O
(	O
noisy	O
frames	B-Protocol
)	O
.	O
</s>
<s>
It	O
uses	O
2-byte	O
Silence	O
Insertion	O
Descriptor	O
(	O
SID	O
)	O
frames	B-Protocol
transmitted	O
to	O
initiate	O
comfort	O
noise	O
generation	O
(	O
CNG	O
)	O
.	O
</s>
<s>
G.729	B-Algorithm
Annex	O
J	O
,	O
maintained	O
by	O
G.729.1	B-Algorithm
,	O
provides	O
support	O
for	O
wideband	O
speech	O
and	O
audio	O
.	O
</s>
<s>
Introduced	O
in	O
2006	O
,	O
it	O
defines	O
variable	B-General_Concept
bit-rate	I-General_Concept
wideband	O
enhancement	O
using	O
up	O
to	O
12	O
hierarchical	O
layers	O
.	O
</s>
<s>
The	O
core	O
layer	O
is	O
an	O
8	O
kbit/s	O
G.729	B-Algorithm
bitstream	O
,	O
the	O
second	O
layer	O
is	O
a	O
4	O
kbit/s	O
narrowband	O
enhancement	O
layer	O
,	O
and	O
the	O
third	O
2	O
kibt/s	O
layer	O
is	O
a	O
bandwidth	O
enhancement	O
layer	O
.	O
</s>
<s>
The	O
G.729.1	B-Algorithm
uses	O
three-stage	O
coding	O
:	O
embedded	O
code-excited	B-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
CELP	B-Algorithm
)	O
coding	O
of	O
the	O
lower	O
band	O
,	O
parametric	O
coding	O
of	O
the	O
higher	O
band	O
by	O
Time-Domain	O
Bandwidth	O
Extension	O
(	O
TDBWE	O
)	O
,	O
and	O
enhancement	O
of	O
the	O
full	O
band	O
by	O
a	O
predictive	O
transform	B-Algorithm
coding	I-Algorithm
algorithm	O
called	O
time-domain	O
aliasing	O
cancellation	O
(	O
TDAC	O
)	O
,	O
also	O
known	O
as	O
modified	O
discrete	O
cosine	O
transform	O
(	O
MDCT	O
)	O
coding	O
.	O
</s>
<s>
As	O
of	O
January	O
1	O
,	O
2017	O
,	O
the	O
patent	O
terms	O
of	O
most	O
licensed	O
patents	O
under	O
the	O
G.729	B-Algorithm
Consortium	O
have	O
expired	O
,	O
the	O
remaining	O
unexpired	O
patents	O
are	O
usable	O
on	O
a	O
royalty-free	O
basis	O
.	O
</s>
<s>
G.729	B-Algorithm
includes	O
patents	O
from	O
several	O
companies	O
which	O
were	O
until	O
the	O
expiry	O
licensed	O
by	O
Sipro	O
Lab	O
Telecom	O
,	O
the	O
authorized	O
Intellectual	O
Property	O
Licensing	O
Administrator	O
for	O
G.729	B-Algorithm
technology	O
and	O
patent	O
pool	O
.	O
</s>
<s>
The	O
'	O
853	O
patent	O
contains	O
patent	O
claims	O
which	O
cover	O
lookup	O
tables	O
used	O
in	O
G.729	B-Algorithm
.	O
</s>
<s>
G.729	B-Algorithm
is	O
assigned	O
the	O
static	O
payload	O
type	O
18	O
for	O
RTP	B-Protocol
by	O
IANA	O
.	O
</s>
<s>
The	O
rtpmap	O
parameter	O
description	O
for	O
this	O
payload	O
type	O
is	O
"	O
G729/8000	O
"	O
.	O
</s>
<s>
Both	O
G.729a	B-Algorithm
and	O
G.729b	O
use	O
the	O
same	O
rtpmap	O
description	O
as	O
G.729	B-Algorithm
.	O
</s>
<s>
G.729a	B-Algorithm
and	O
G.729b	O
are	O
indicated	O
using	O
annexb	O
=	O
no	O
or	O
annexb	O
=	O
yes	O
,	O
respectively	O
.	O
</s>
<s>
G.729	B-Algorithm
Annex	O
B	O
(	O
G.729b	O
)	O
is	O
the	O
default	O
in	O
absence	O
of	O
parameter	O
annexb	O
in	O
the	O
Session	B-Language
Description	I-Language
Protocol	I-Language
.	O
</s>
