<s>
Siren	B-Algorithm
is	O
a	O
family	O
of	O
patented	O
,	O
transform-based	O
,	O
wideband	B-Algorithm
audio	I-Algorithm
coding	O
formats	O
and	O
their	O
audio	B-Algorithm
codec	I-Algorithm
implementations	O
developed	O
and	O
licensed	O
by	O
PictureTel	B-Application
Corporation	I-Application
(	O
acquired	O
by	O
Polycom	O
,	O
Inc	O
.	O
in	O
2001	O
)	O
.	O
</s>
<s>
There	O
are	O
three	O
Siren	B-Algorithm
codecs	I-Algorithm
:	O
Siren	B-Algorithm
7	I-Algorithm
,	O
Siren	B-Algorithm
14	I-Algorithm
and	O
Siren	B-Algorithm
22	I-Algorithm
.	O
</s>
<s>
Siren	B-Algorithm
7	I-Algorithm
(	O
or	O
Siren7	O
or	O
simply	O
Siren	B-Algorithm
)	O
provides	O
7kHz	O
audio	O
,	O
bit	O
rates	O
16	O
,	O
24	O
,	O
32	O
kbit/s	O
and	O
sampling	B-Algorithm
frequency	I-Algorithm
16kHz	O
.	O
</s>
<s>
Siren	B-Algorithm
is	O
derived	O
from	O
PictureTel	B-Application
's	O
PT716plus	O
algorithm	O
.	O
</s>
<s>
In	O
1999	O
,	O
ITU-T	O
approved	O
G.722.1	B-Algorithm
recommendation	O
,	O
which	O
is	O
based	O
on	O
Siren	B-Algorithm
7	I-Algorithm
algorithm	O
.	O
</s>
<s>
G.722.1	B-Algorithm
provides	O
only	O
bit	O
rates	O
24	O
and	O
32	O
kbit/s	O
and	O
does	O
not	O
support	O
Siren	B-Algorithm
7	I-Algorithm
's	O
bit	O
rate	O
16	O
kbit/s	O
.	O
</s>
<s>
The	O
algorithm	O
of	O
Siren	B-Algorithm
7	I-Algorithm
is	O
identical	O
to	O
its	O
successor	O
,	O
G.722.1	B-Algorithm
,	O
although	O
the	O
data	O
formats	O
are	O
slightly	O
different	O
.	O
</s>
<s>
Siren	B-Algorithm
14	I-Algorithm
(	O
or	O
Siren14	O
)	O
provides	O
14kHz	O
audio	O
,	O
bit	O
rates	O
24	O
,	O
32	O
,	O
48	O
kbit/s	O
for	O
mono	O
,	O
48	O
,	O
64	O
,	O
96	O
kbit/s	O
for	O
stereo	O
and	O
sampling	B-Algorithm
frequency	I-Algorithm
32kHz	O
.	O
</s>
<s>
Siren	B-Algorithm
14	I-Algorithm
supports	O
stereo	O
and	O
mono	O
audio	O
.	O
</s>
<s>
The	O
mono	O
version	O
of	O
Siren	B-Algorithm
14	I-Algorithm
became	O
ITU-T	O
G.722.1C	O
(	O
14kHz	O
,	O
24/32/48	O
kbit/s	O
)	O
in	O
April	O
2005	O
.	O
</s>
<s>
The	O
algorithm	O
is	O
based	O
on	O
transform	B-Algorithm
coding	I-Algorithm
technology	O
,	O
using	O
a	O
modulated	O
lapped	O
transform	O
(	O
MLT	O
)	O
,	O
a	O
type	O
of	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
or	O
modified	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
MDCT	O
)	O
.	O
</s>
<s>
Siren	B-Algorithm
22	I-Algorithm
(	O
or	O
Siren22	O
)	O
provides	O
22kHz	O
audio	O
,	O
sampling	B-Algorithm
frequency	I-Algorithm
48kHz	O
,	O
bit	O
rates	O
64	O
,	O
96	O
,	O
128	O
kbit/s	O
stereo	O
and	O
32	O
,	O
48	O
,	O
64	O
kbit/s	O
mono	O
.	O
</s>
<s>
Siren	B-Algorithm
22	I-Algorithm
offers	O
40	O
millisecond	O
algorithmic	O
delay	O
using	O
20	O
millisecond	O
frame	O
lengths	O
.	O
</s>
<s>
In	O
May	O
2008	O
,	O
ITU-T	O
approved	O
the	O
new	O
G.719	B-Algorithm
full-band	O
codec	O
which	O
is	O
based	O
on	O
Polycom	O
Siren	B-Algorithm
22	I-Algorithm
audio	O
technology	O
and	O
Ericsson	O
's	O
advanced	O
audio	O
techniques	O
.	O
</s>
<s>
Siren	B-Algorithm
7	I-Algorithm
is	O
commonly	O
used	O
in	O
videoconferencing	O
systems	O
and	O
is	O
also	O
part	O
of	O
Microsoft	B-Protocol
Office	I-Protocol
Communicator	I-Protocol
when	O
using	O
A/V	O
conferencing	O
.	O
</s>
<s>
Microsoft	B-Protocol
Office	I-Protocol
Communications	I-Protocol
Server	I-Protocol
uses	O
Siren	B-Algorithm
7	I-Algorithm
during	O
audio	O
conferencing	O
.	O
</s>
<s>
With	O
the	O
default	O
Office	B-Protocol
Communicator	I-Protocol
client	O
,	O
point	O
to	O
point	O
audio	O
is	O
by	O
default	O
performed	O
using	O
Microsoft	O
's	O
proprietary	O
codec	O
RTAudio	B-Algorithm
.	O
</s>
<s>
When	O
a	O
call	O
is	O
promoted	O
into	O
an	O
audio	O
conference	O
(	O
any	O
time	O
3	O
or	O
more	O
participants	O
have	O
joined	O
)	O
,	O
the	O
codec	O
is	O
switched	O
on	O
the	O
fly	O
to	O
Siren	B-Algorithm
.	O
</s>
<s>
In	O
Windows	O
XP	O
and	O
later	O
versions	O
of	O
Windows	O
,	O
the	O
Siren	B-Algorithm
7	I-Algorithm
codec	O
is	O
implemented	O
in	O
.	O
</s>
<s>
FreeSWITCH	B-Language
communication	O
open	O
source	O
software	O
can	O
do	O
transcoding	O
,	O
conferencing	O
and	O
bridging	O
of	O
Siren	O
7/G.722.1	O
and	O
Siren	O
14/G.722.1C	O
audio	O
formats	O
.	O
</s>
<s>
aMSN	B-Protocol
,	O
an	O
open	O
source	O
Windows	O
Live	O
Messenger	O
clone	O
uses	O
for	O
Siren	B-Algorithm
audio	O
compression	O
and	O
decompression	O
the	O
"	O
libsiren	O
"	O
library	O
,	O
an	O
open	O
source	O
implementation	O
of	O
the	O
codec	O
,	O
written	O
by	O
aMSN	B-Protocol
developer	O
Youness	O
Alaoui	O
(	O
KaKaRoTo	O
)	O
.	O
</s>
<s>
The	O
libsiren	O
library	O
has	O
also	O
been	O
copied	O
into	O
libmsn	O
and	O
into	O
the	O
msn-pecan	O
project	O
,	O
which	O
provides	O
plug-in	O
for	O
Pidgin	B-Protocol
and	O
Adium	B-Protocol
instant	O
messaging	O
clients	O
.	O
</s>
<s>
Usage	O
of	O
Siren	B-Algorithm
7	I-Algorithm
and	O
Siren	B-Algorithm
14	I-Algorithm
audio	O
coding	O
formats	O
require	O
the	O
licensing	O
of	O
patents	O
from	O
Polycom	O
,	O
in	O
most	O
countries	O
.	O
</s>
<s>
A	O
royalty	O
free	O
licence	O
for	O
Siren	B-Algorithm
7	I-Algorithm
and	O
Siren	B-Algorithm
14	I-Algorithm
is	O
available	O
from	O
Polycom	O
if	O
certain	O
fairly	O
basic	O
conditions	O
are	O
met	O
.	O
</s>
<s>
Usage	O
of	O
Siren	B-Algorithm
22	I-Algorithm
also	O
requires	O
the	O
licensing	O
of	O
patents	O
from	O
Polycom	O
.	O
</s>
