<s>
Algebraic	B-Algorithm
code-excited	I-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
ACELP	B-Algorithm
)	O
is	O
a	O
speech	B-Application
coding	I-Application
algorithm	O
in	O
which	O
a	O
limited	O
set	O
of	O
pulses	O
is	O
distributed	O
as	O
excitation	O
to	O
a	O
linear	B-Algorithm
prediction	I-Algorithm
filter	O
.	O
</s>
<s>
It	O
is	O
a	O
linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
(	O
LPC	O
)	O
algorithm	O
that	O
is	O
based	O
on	O
the	O
code-excited	B-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
CELP	B-Algorithm
)	O
method	O
and	O
has	O
an	O
algebraic	O
structure	O
.	O
</s>
<s>
ACELP	B-Algorithm
was	O
developed	O
in	O
1989	O
by	O
the	O
researchers	O
at	O
the	O
Université	O
de	O
Sherbrooke	O
in	O
Canada	O
.	O
</s>
<s>
The	O
ACELP	B-Algorithm
method	O
is	O
widely	O
employed	O
in	O
current	O
speech	B-Application
coding	I-Application
standards	O
such	O
as	O
AMR	B-Algorithm
,	O
EFR	B-Algorithm
,	O
AMR-WB	B-Algorithm
(	O
G.722.2	B-Algorithm
)	O
,	O
VMR-WB	B-Algorithm
,	O
EVRC	B-Algorithm
,	O
EVRC-B	B-Algorithm
,	O
SMV	O
,	O
TETRA	O
,	O
PCS	O
1900	O
,	O
MPEG-4	B-Algorithm
CELP	B-Algorithm
and	O
ITU-T	O
G-series	O
standards	O
G.729	B-Algorithm
,	O
G.729.1	B-Algorithm
(	O
first	O
coding	O
stage	O
)	O
and	O
G.723.1	B-Algorithm
.	O
</s>
<s>
The	O
ACELP	B-Algorithm
algorithm	O
is	O
also	O
used	O
in	O
the	O
proprietary	O
ACELP.net	O
codec	O
.	O
</s>
<s>
Audible	B-Application
Inc	I-Application
.	I-Application
use	O
a	O
modified	O
version	O
for	O
their	O
speaking	O
books	O
.	O
</s>
<s>
The	O
ACELP	B-Algorithm
patent	O
expired	O
in	O
2018	O
and	O
is	O
now	O
royalty-free	O
.	O
</s>
<s>
The	O
main	O
advantage	O
of	O
ACELP	B-Algorithm
is	O
that	O
the	O
algebraic	O
codebook	O
it	O
uses	O
can	O
be	O
made	O
very	O
large	O
(	O
>	O
50	O
bits	O
)	O
without	O
running	O
into	O
storage	O
(	O
RAM/ROM	O
)	O
or	O
complexity	O
(	O
CPU	B-Device
time	O
)	O
problems	O
.	O
</s>
<s>
The	O
ACELP	B-Algorithm
algorithm	O
is	O
based	O
on	O
that	O
used	O
in	O
code-excited	B-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
CELP	B-Algorithm
)	O
,	O
but	O
ACELP	B-Algorithm
codebooks	O
have	O
a	O
specific	O
algebraic	O
structure	O
imposed	O
upon	O
them	O
.	O
</s>
<s>
In	O
ACELP	B-Algorithm
,	O
a	O
block	O
of	O
N	O
speech	O
samples	O
is	O
synthesized	O
by	O
filtering	O
an	O
appropriate	O
innovation	O
sequence	O
from	O
a	O
codebook	O
,	O
scaled	O
by	O
a	O
gain	O
factor	O
g	O
c	O
,	O
through	O
two	O
time-varying	O
filters	O
.	O
</s>
