<s>
Speex	B-Application
is	O
an	O
audio	O
compression	B-General_Concept
codec	O
specifically	O
tuned	O
for	O
the	O
reproduction	O
of	O
human	O
speech	O
and	O
also	O
a	O
free	B-Application
software	I-Application
speech	B-Application
codec	I-Application
that	O
may	O
be	O
used	O
on	O
VoIP	B-Application
applications	O
and	O
podcasts	B-Operating_System
.	O
</s>
<s>
It	O
is	O
based	O
on	O
the	O
CELP	B-Algorithm
speech	B-Application
coding	I-Application
algorithm	O
.	O
</s>
<s>
Its	O
creators	O
claim	O
Speex	B-Application
to	O
be	O
free	O
of	O
any	O
patent	O
restrictions	O
and	O
it	O
is	O
licensed	O
under	O
the	O
revised	O
(	O
3-clause	O
)	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
It	O
may	O
be	O
used	O
with	O
the	O
Ogg	O
container	O
format	O
or	O
directly	O
transmitted	O
over	O
UDP/RTP	O
.	O
</s>
<s>
It	O
may	O
also	O
be	O
used	O
with	O
the	O
FLV	B-Operating_System
container	O
format	O
.	O
</s>
<s>
The	O
Speex	B-Application
designers	O
see	O
their	O
project	O
as	O
complementary	O
to	O
the	O
Vorbis	B-Algorithm
general-purpose	O
audio	O
compression	B-General_Concept
project	O
.	O
</s>
<s>
Speex	B-Application
is	O
a	O
lossy	B-Algorithm
format	O
,	O
i.e.	O
</s>
<s>
The	O
Speex	B-Application
project	O
was	O
created	O
on	O
February	O
13	O
,	O
2002	O
.	O
</s>
<s>
The	O
first	O
development	O
versions	O
of	O
Speex	B-Application
were	O
released	O
under	O
LGPL	B-Application
license	I-Application
,	O
but	O
as	O
of	O
version	O
1.0	O
beta	O
1	O
,	O
Speex	B-Application
is	O
released	O
under	O
Xiph	B-Application
's	O
version	O
of	O
the	O
(	O
revised	O
)	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Speex	B-Application
1.0	O
was	O
announced	O
on	O
March	O
24	O
,	O
2003	O
,	O
after	O
a	O
year	O
of	O
development	O
.	O
</s>
<s>
The	O
last	O
stable	O
version	O
of	O
Speex	B-Application
encoder	O
and	O
decoder	O
is	O
1.2.1	O
.	O
</s>
<s>
Xiph.Org	B-Application
now	O
considers	O
Speex	B-Application
obsolete	O
;	O
its	O
successor	O
is	O
the	O
more	O
modern	O
Opus	B-Algorithm
codec	I-Algorithm
,	O
which	O
uses	O
the	O
SILK	O
format	O
under	O
license	O
from	O
Microsoft	O
and	O
surpasses	O
its	O
performance	O
in	O
most	O
areas	O
except	O
at	O
the	O
lowest	O
sample	O
rates	O
.	O
</s>
<s>
Speex	B-Application
is	O
targeted	O
at	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
and	O
file-based	O
compression	B-General_Concept
.	O
</s>
<s>
Since	O
Speex	B-Application
was	O
designed	O
for	O
VoIP	B-Application
instead	O
of	O
cell	O
phone	O
use	O
,	O
the	O
codec	O
must	O
be	O
robust	O
to	O
lost	O
packets	O
,	O
but	O
not	O
to	O
corrupted	O
ones	O
.	O
</s>
<s>
All	O
this	O
led	O
to	O
the	O
choice	O
of	O
code	B-Algorithm
excited	I-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
CELP	B-Algorithm
)	O
as	O
the	O
encoding	O
technique	O
to	O
use	O
for	O
Speex	B-Application
.	O
</s>
<s>
One	O
of	O
the	O
main	O
reasons	O
is	O
that	O
CELP	B-Algorithm
has	O
long	O
proven	O
that	O
it	O
could	O
do	O
the	O
job	O
and	O
scale	O
well	O
to	O
both	O
low	O
bit	O
rates	O
(	O
as	O
evidenced	O
by	O
DoD	O
CELP	B-Algorithm
@	O
4.8kbit/s	O
)	O
and	O
high	O
bit	O
rates	O
(	O
as	O
with	O
G.728	B-Algorithm
@	O
16kbit/s	O
)	O
.	O
</s>
<s>
Free	O
software/open	O
-source	O
,	O
patent	O
and	O
royalty-free	O
.	O
</s>
<s>
Dynamic	O
bit	O
rate	O
switching	O
and	O
variable	B-General_Concept
bit-rate	I-General_Concept
(	O
VBR	O
)	O
.	O
</s>
<s>
Voice	B-General_Concept
activity	I-General_Concept
detection	I-General_Concept
(	O
VAD	O
,	O
integrated	O
with	O
VBR	O
)	O
(	O
not	O
working	O
from	O
version	O
1.2	O
)	O
.	O
</s>
<s>
Sampling	O
rate	O
Speex	B-Application
is	O
mainly	O
designed	O
for	O
three	O
different	O
sampling	O
rates	O
:	O
8kHz	O
(	O
the	O
same	O
sampling	O
rate	O
to	O
transmit	O
telephone	O
calls	O
)	O
,	O
16kHz	O
,	O
and	O
32kHz	O
.	O
</s>
<s>
Quality	O
Speex	B-Application
encoding	I-Application
is	O
controlled	O
most	O
of	O
the	O
time	O
by	O
a	O
quality	O
parameter	O
that	O
ranges	O
from	O
0	O
to	O
10	O
.	O
</s>
<s>
In	O
constant	O
bit-rate	O
(	O
CBR	O
)	O
operation	O
,	O
the	O
quality	O
parameter	O
is	O
an	O
integer	O
,	O
while	O
for	O
variable	B-General_Concept
bit-rate	I-General_Concept
(	O
VBR	O
)	O
,	O
the	O
parameter	O
is	O
a	O
real	O
(	O
floating	B-Algorithm
point	I-Algorithm
)	O
number	O
.	O
</s>
<s>
Complexity	O
(	O
variable	O
)	O
With	O
Speex	B-Application
,	O
it	O
is	O
possible	O
to	O
vary	O
the	O
complexity	O
allowed	O
for	O
the	O
encoder	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
controlling	O
how	O
the	O
search	O
is	O
performed	O
with	O
an	O
integer	O
ranging	O
from	O
1	O
to	O
10	O
in	O
a	O
way	O
similar	O
to	O
the	O
-1	O
to	O
-9	O
options	O
to	O
gzip	B-Application
compression	I-Application
utilities	O
.	O
</s>
<s>
For	O
normal	O
use	O
,	O
the	O
noise	O
level	O
at	O
complexity	O
1	O
is	O
between	O
1	O
and	O
2dB	O
higher	O
than	O
at	O
complexity	O
10	O
,	O
but	O
the	O
CPU	B-General_Concept
requirements	O
for	O
complexity	O
10	O
is	O
about	O
five	O
times	O
higher	O
than	O
for	O
complexity	O
1	O
.	O
</s>
<s>
Variable	B-General_Concept
bit-rate	I-General_Concept
(	O
VBR	O
)	O
Variable	B-General_Concept
bit-rate	I-General_Concept
(	O
VBR	O
)	O
allows	O
a	O
codec	O
to	O
change	O
its	O
bit	O
rate	O
dynamically	O
to	O
adapt	O
to	O
the	O
"	O
difficulty	O
"	O
of	O
the	O
audio	O
being	O
encoded	O
.	O
</s>
<s>
In	O
the	O
example	O
of	O
Speex	B-Application
,	O
sounds	O
like	O
vowels	O
and	O
high-energy	O
transients	O
require	O
a	O
higher	O
bit	O
rate	O
to	O
achieve	O
good	O
quality	O
,	O
while	O
fricatives	O
(	O
e.g.	O
</s>
<s>
Second	O
,	O
for	O
some	O
real-time	O
applications	O
like	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
,	O
what	O
counts	O
is	O
the	O
maximum	O
bit-rate	O
,	O
which	O
must	O
be	O
low	O
enough	O
for	O
the	O
communication	O
channel	O
.	O
</s>
<s>
Voice	B-General_Concept
Activity	I-General_Concept
Detection	I-General_Concept
(	O
VAD	O
)	O
When	O
enabled	O
,	O
voice	B-General_Concept
activity	I-General_Concept
detection	I-General_Concept
detects	O
whether	O
the	O
audio	O
being	O
encoded	O
is	O
speech	O
or	O
silence/background	O
noise	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
Speex	B-Application
detects	O
non-speech	O
periods	O
and	O
encodes	O
them	O
with	O
just	O
enough	O
bits	O
to	O
reproduce	O
the	O
background	O
noise	O
.	O
</s>
<s>
For	O
Speex	B-Application
,	O
this	O
delay	O
is	O
equal	O
to	O
the	O
frame	O
size	O
,	O
plus	O
some	O
amount	O
of	O
"	O
look-ahead	O
"	O
required	O
to	O
process	O
each	O
frame	O
.	O
</s>
<s>
These	O
values	O
do	O
not	O
account	O
for	O
the	O
CPU	B-General_Concept
time	O
it	O
takes	O
to	O
encode	O
or	O
decode	O
the	O
frames	O
.	O
</s>
<s>
There	O
are	O
a	O
large	O
base	O
of	O
applications	O
supporting	O
the	O
Speex	B-Application
codec	O
.	O
</s>
<s>
VoIP	B-Application
systems	O
(	O
e.g.	O
</s>
<s>
Xbox	B-Application
Live	I-Application
,	O
Civilization	B-Application
4	I-Application
,	O
DropMix	B-Application
vocal	O
tracks	O
,	O
...	O
)	O
</s>
<s>
Most	O
of	O
these	O
are	O
based	O
on	O
the	O
DirectShow	B-Library
filter	O
or	O
OpenACM	O
codec	O
(	O
e.g.	O
</s>
<s>
Microsoft	B-Protocol
NetMeeting	I-Protocol
)	O
on	O
Microsoft	B-Application
Windows	I-Application
,	O
or	O
org	O
's	O
reference	O
implementation	O
,	O
libvorbis	B-Algorithm
,	O
on	O
Linux	B-Application
(	O
e.g.	O
</s>
<s>
Ekiga	B-Language
)	O
.	O
</s>
<s>
There	O
are	O
also	O
plugins	B-Application
for	O
many	O
audio	O
players	O
.	O
</s>
<s>
See	O
the	O
plugin	B-Application
and	O
software	O
page	O
on	O
the	O
speex.org	O
site	O
for	O
more	O
details	O
.	O
</s>
<s>
The	O
media	O
type	O
for	O
Speex	B-Application
is	O
audio/ogg	O
while	O
contained	O
by	O
Ogg	O
,	O
and	O
audio/speex	O
(	O
previously	O
audio/x	O
-speex	O
)	O
when	O
transported	O
through	O
RTP	B-Protocol
or	O
without	O
container	O
.	O
</s>
<s>
The	O
United	O
States	O
Army	O
's	O
Land	B-Application
Warrior	I-Application
system	I-Application
,	O
designed	O
by	O
General	O
Dynamics	O
,	O
also	O
uses	O
Speex	B-Application
for	O
VoIP	B-Application
on	O
an	O
EPLRS	O
radio	O
designed	O
by	O
Raytheon	O
.	O
</s>
<s>
The	O
Ear	O
Bible	O
is	O
a	O
single-ear	O
headphone	O
with	O
a	O
built-in	O
Speex	B-Application
player	O
with	O
1	O
GB	O
of	O
flash	O
memory	O
,	O
preloaded	O
with	O
a	O
recording	O
of	O
the	O
New	O
American	O
Standard	O
Bible	O
.	O
</s>
<s>
ASL	O
Safety	O
&	O
Security	O
's	O
Linux	B-Application
based	O
VIPA	O
OS	O
software	O
which	O
is	O
used	O
in	O
long	O
line	O
public	O
address	O
systems	O
and	O
voice	O
alarm	O
systems	O
at	O
major	O
international	O
air	O
transport	O
hubs	O
and	O
rail	O
networks	O
.	O
</s>
<s>
The	O
Rockbox	B-Application
project	O
uses	O
Speex	B-Application
for	O
its	O
voice	O
interface	O
.	O
</s>
<s>
It	O
can	O
also	O
play	O
Speex	B-Application
files	O
on	O
supported	O
players	O
,	O
such	O
as	O
the	O
Apple	O
iPod	O
or	O
the	O
iRiver	O
H10	O
.	O
</s>
<s>
The	O
Vernier	O
LabQuest	O
handheld	O
data	O
acquisition	O
device	O
for	O
science	O
education	O
uses	O
Speex	B-Application
for	O
voice	O
annotations	O
created	O
by	O
students	O
and	O
teachers	O
using	O
either	O
the	O
built-in	O
or	O
an	O
external	O
microphone	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Mobile	O
App	O
for	O
iPhone	B-Operating_System
currently	O
incorporates	O
Speex	B-Application
.	O
</s>
<s>
It	O
has	O
also	O
been	O
suggested	O
that	O
the	O
new	O
Google	B-Application
voice	O
search	O
iPhone	B-Operating_System
app	O
is	O
using	O
Speex	B-Application
to	O
transmit	O
voice	O
to	O
Google	B-Application
servers	O
for	O
interpretation	O
.	O
</s>
<s>
Adobe	B-Operating_System
Flash	I-Operating_System
Player	I-Operating_System
supports	O
Speex	B-Application
starting	O
with	O
Flash	B-Operating_System
Player	I-Operating_System
10.0.12.36	O
,	O
released	O
in	O
October	O
2008	O
.	O
</s>
<s>
Because	O
of	O
some	O
bugs	O
in	O
Flash	B-Operating_System
Player	I-Operating_System
,	O
the	O
first	O
recommended	O
version	O
for	O
Speex	B-Application
support	O
is	O
10.0.22.87	O
and	O
later	O
.	O
</s>
<s>
Speex	B-Application
in	O
Flash	B-Operating_System
Player	I-Operating_System
can	O
be	O
used	O
for	O
both	O
kind	O
of	O
communication	O
,	O
through	O
Flash	B-Operating_System
Media	I-Operating_System
Server	I-Operating_System
or	O
P2P	O
.	O
</s>
<s>
Speex	B-Application
can	O
be	O
decoded	O
or	O
converted	O
to	O
any	O
format	O
unlike	O
Nellymoser	B-Algorithm
audio	O
,	O
which	O
was	O
the	O
only	O
speech	O
format	O
in	O
previous	O
versions	O
of	O
Flash	B-Operating_System
Player	I-Operating_System
.	O
</s>
<s>
Speex	B-Application
can	O
be	O
also	O
used	O
in	O
the	O
Flash	B-Operating_System
Video	I-Operating_System
container	O
format	O
(	O
.flv	B-Operating_System
)	O
,	O
starting	O
with	O
version	O
10	O
of	O
Video	O
File	O
Format	O
Specification	O
(	O
published	O
in	O
November	O
2008	O
)	O
.	O
</s>
<s>
The	O
JavaSonics	O
ListenUp	O
voice	O
recorder	O
uses	O
Speex	B-Application
to	O
compress	O
voice	O
messages	O
that	O
are	O
recorded	O
in	O
a	O
browser	O
and	O
then	O
uploaded	O
to	O
a	O
web	O
server	O
.	O
</s>
<s>
Speex	B-Application
is	O
used	O
as	O
the	O
voice	O
compression	B-General_Concept
algorithm	I-General_Concept
in	O
the	O
Siri	B-Application
voice	O
assistance	O
on	O
the	O
iPhone	B-Operating_System
4S	I-Operating_System
.	O
</s>
<s>
Since	O
text-to-speech	O
occurs	O
on	O
Apple	O
's	O
servers	O
,	O
the	O
Speex	B-Application
codec	O
is	O
used	O
to	O
minimize	O
network	O
bandwidth	O
.	O
</s>
