<s>
Linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
(	O
LPC	O
)	O
is	O
a	O
method	O
used	O
mostly	O
in	O
audio	B-Algorithm
signal	I-Algorithm
processing	I-Algorithm
and	O
speech	B-Algorithm
processing	I-Algorithm
for	O
representing	O
the	O
spectral	O
envelope	O
of	O
a	O
digital	B-General_Concept
signal	O
of	O
speech	O
in	O
compressed	B-General_Concept
form	O
,	O
using	O
the	O
information	O
of	O
a	O
linear	O
predictive	B-General_Concept
model	I-General_Concept
.	O
</s>
<s>
LPC	O
is	O
the	O
most	O
widely	O
used	O
method	O
in	O
speech	B-Application
coding	I-Application
and	O
speech	B-Application
synthesis	I-Application
.	O
</s>
<s>
Although	O
apparently	O
crude	O
,	O
this	O
Source	B-Application
–	I-Application
filter	I-Application
model	I-Application
is	O
actually	O
a	O
close	O
approximation	O
of	O
the	O
reality	O
of	O
speech	O
production	O
.	O
</s>
<s>
The	O
glottis	B-Application
(	O
the	O
space	O
between	O
the	O
vocal	O
folds	O
)	O
produces	O
the	O
buzz	O
,	O
which	O
is	O
characterized	O
by	O
its	O
intensity	O
(	O
loudness	B-Algorithm
)	O
and	O
frequency	O
(	O
pitch	O
)	O
.	O
</s>
<s>
In	O
1969	O
,	O
Itakura	O
and	O
Saito	O
introduced	O
method	O
based	O
on	O
partial	B-Language
correlation	I-Language
(	O
PARCOR	O
)	O
,	O
Glen	O
Culler	O
proposed	O
real-time	O
speech	B-Application
encoding	I-Application
,	O
and	O
Bishnu	O
S	O
.	O
Atal	O
presented	O
an	O
LPC	O
speech	B-Application
coder	I-Application
at	O
the	O
Annual	O
Meeting	O
of	O
the	O
Acoustical	O
Society	O
of	O
America	O
.	O
</s>
<s>
of	O
BBN	O
developed	O
the	O
first	O
variable-rate	B-General_Concept
LPC	O
algorithm	O
.	O
</s>
<s>
The	O
same	O
year	O
,	O
Atal	O
and	O
Manfred	O
R	O
.	O
Schroeder	O
at	O
Bell	O
Labs	O
proposed	O
an	O
LPC	O
speech	B-Application
codec	I-Application
called	O
adaptive	O
predictive	O
coding	O
,	O
which	O
used	O
a	O
psychoacoustic	O
coding	O
algorithm	O
exploiting	O
the	O
masking	O
properties	O
of	O
the	O
human	O
ear	O
.	O
</s>
<s>
This	O
later	O
became	O
the	O
basis	O
for	O
the	O
perceptual	O
coding	O
technique	O
used	O
by	O
the	O
MP3	B-Application
audio	I-Application
compression	O
format	O
,	O
introduced	O
in	O
1993	O
.	O
</s>
<s>
Code-excited	B-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
CELP	B-Algorithm
)	O
was	O
developed	O
by	O
Schroeder	O
and	O
Atal	O
in	O
1985	O
.	O
</s>
<s>
LPC	O
is	O
the	O
basis	O
for	O
voice-over-IP	B-Application
(	O
VoIP	B-Application
)	O
technology	O
.	O
</s>
<s>
In	O
1972	O
,	O
Bob	O
Kahn	O
of	O
ARPA	O
,	O
with	O
Jim	O
Forgie	O
(	O
Lincoln	O
Laboratory	O
,	O
LL	O
)	O
and	O
Dave	O
Walden	O
(	O
BBN	O
Technologies	O
)	O
,	O
started	O
the	O
first	O
developments	O
in	O
packetized	O
speech	O
,	O
which	O
would	O
eventually	O
lead	O
to	O
voice-over-IP	B-Application
technology	O
.	O
</s>
<s>
In	O
1976	O
,	O
the	O
first	O
LPC	O
conference	O
took	O
place	O
over	O
the	O
ARPANET	O
using	O
the	O
Network	B-Protocol
Voice	I-Protocol
Protocol	I-Protocol
,	O
between	O
Culler-Harrison	O
,	O
ISI	O
,	O
SRI	O
,	O
and	O
LL	O
at	O
3500	O
bit/s	O
.	O
</s>
<s>
There	O
are	O
more	O
advanced	O
representations	O
such	O
as	O
log	B-Algorithm
area	I-Algorithm
ratios	I-Algorithm
(	O
LAR	O
)	O
,	O
line	B-Algorithm
spectral	I-Algorithm
pairs	I-Algorithm
(	O
LSP	O
)	O
decomposition	O
and	O
reflection	O
coefficients	O
.	O
</s>
<s>
LPC	O
is	O
the	O
most	O
widely	O
used	O
method	O
in	O
speech	B-Application
coding	I-Application
and	O
speech	B-Application
synthesis	I-Application
.	O
</s>
<s>
It	O
is	O
also	O
used	O
for	O
secure	O
wireless	O
,	O
where	O
voice	O
must	O
be	O
digitized	O
,	O
encrypted	O
and	O
sent	O
over	O
a	O
narrow	O
voice	O
channel	O
;	O
an	O
early	O
example	O
of	O
this	O
is	O
the	O
US	O
government	O
's	O
Navajo	B-General_Concept
I	I-General_Concept
.	O
</s>
<s>
LPC	O
synthesis	O
can	O
be	O
used	O
to	O
construct	O
vocoders	B-Application
where	O
musical	O
instruments	O
are	O
used	O
as	O
an	O
excitation	O
signal	O
to	O
the	O
time-varying	O
filter	O
estimated	O
from	O
a	O
singer	O
's	O
speech	O
.	O
</s>
<s>
Paul	O
Lansky	O
made	O
the	O
well-known	O
computer	O
music	O
piece	O
notjustmoreidlechatter	O
using	O
linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
.	O
</s>
<s>
A	O
10th-order	O
LPC	O
was	O
used	O
in	O
the	O
popular	O
1980s	O
Speak	B-Application
&	I-Application
Spell	I-Application
educational	O
toy	O
.	O
</s>
<s>
LPC	O
predictors	O
are	O
used	O
in	O
Shorten	B-Operating_System
,	O
MPEG-4	B-Algorithm
ALS	I-Algorithm
,	O
FLAC	B-Application
,	O
SILK	O
audio	B-Algorithm
codec	I-Algorithm
,	O
and	O
other	O
lossless	B-Algorithm
audio	B-Algorithm
codecs	I-Algorithm
.	O
</s>
