<s>
The	O
Adaptive	B-Algorithm
Multi-Rate	I-Algorithm
(	O
AMR	O
,	O
AMR-NB	B-Algorithm
or	O
GSM-AMR	B-Algorithm
)	O
audio	O
codec	B-General_Concept
is	O
an	O
audio	O
compression	O
format	O
optimized	O
for	O
speech	B-Application
coding	I-Application
.	O
</s>
<s>
AMR	O
is	O
a	O
multi-rate	O
narrowband	O
speech	B-Application
codec	I-Application
that	O
encodes	O
narrowband	O
(	O
200	O
–	O
3400Hz	O
)	O
signals	O
at	O
variable	O
bit	O
rates	O
ranging	O
from	O
4.75	O
to	O
12.2kbit/s	O
with	O
toll	O
quality	O
speech	O
starting	O
at	O
7.4kbit/s	O
.	O
</s>
<s>
AMR	O
was	O
adopted	O
as	O
the	O
standard	O
speech	B-Application
codec	I-Application
by	O
3GPP	O
in	O
October	O
1999	O
and	O
is	O
now	O
widely	O
used	O
in	O
GSM	O
and	O
UMTS	B-Protocol
.	O
</s>
<s>
It	O
uses	O
link	B-Protocol
adaptation	I-Protocol
to	O
select	O
from	O
one	O
of	O
eight	O
different	O
bit	O
rates	O
based	O
on	O
link	O
conditions	O
.	O
</s>
<s>
AMR	O
is	O
also	O
a	O
file	O
format	O
for	O
storing	O
spoken	O
audio	O
using	O
the	O
AMR	O
codec	B-General_Concept
.	O
</s>
<s>
Many	O
modern	O
mobile	O
telephone	O
handsets	O
can	O
store	O
short	O
audio	O
recordings	O
in	O
the	O
AMR	O
format	O
,	O
and	O
both	O
free	B-Application
and	O
proprietary	O
programs	O
exist	O
(	O
see	O
Software	O
support	O
)	O
to	O
convert	O
between	O
this	O
and	O
other	O
formats	O
,	O
although	O
AMR	O
is	O
a	O
speech	O
format	O
and	O
is	O
unlikely	O
to	O
give	O
ideal	O
results	O
for	O
other	O
audio	O
.	O
</s>
<s>
The	O
common	O
filename	O
extension	O
is	O
.amr	B-Algorithm
.	O
</s>
<s>
AMR	O
uses	O
various	O
techniques	O
,	O
such	O
as	O
ACELP	B-Algorithm
,	O
DTX	O
,	O
VAD	B-General_Concept
and	O
CNG	O
.	O
</s>
<s>
The	O
usage	O
of	O
AMR	O
requires	O
optimized	O
link	B-Protocol
adaptation	I-Protocol
that	O
selects	O
the	O
best	O
codec	B-General_Concept
mode	O
to	O
meet	O
the	O
local	O
radio	O
channel	O
and	O
capacity	O
requirements	O
.	O
</s>
<s>
If	O
the	O
radio	O
conditions	O
are	O
bad	O
,	O
source	B-General_Concept
coding	I-General_Concept
is	O
reduced	O
and	O
channel	O
coding	O
is	O
increased	O
.	O
</s>
<s>
There	O
are	O
a	O
total	O
of	O
14	O
modes	O
of	O
the	O
AMR	O
codec	B-General_Concept
,	O
eight	O
are	O
available	O
in	O
a	O
full	B-Algorithm
rate	I-Algorithm
channel	O
(	O
FR	O
)	O
and	O
six	O
on	O
a	O
half	B-Algorithm
rate	I-Algorithm
channel	O
(	O
HR	O
)	O
.	O
</s>
<s>
The	O
AMR	O
codec	B-General_Concept
uses	O
eight	O
source	O
codecs	B-General_Concept
with	O
bit-rates	O
of	O
12.2	O
,	O
10.2	O
,	O
7.95	O
,	O
7.40	O
,	O
6.70	O
,	O
5.90	O
,	O
5.15	O
and	O
4.75kbit/s	O
.	O
</s>
<s>
Linear	B-Algorithm
predictive	I-Algorithm
coding	I-Algorithm
(	O
LPC	O
)	O
is	O
used	O
to	O
synthesize	O
the	O
speech	O
from	O
a	O
residual	O
waveform	O
.	O
</s>
<s>
The	O
LPC	O
parameters	O
are	O
encoded	O
as	O
line	B-Algorithm
spectral	I-Algorithm
pairs	I-Algorithm
(	O
LSP	O
)	O
.	O
</s>
<s>
The	O
residual	O
waveform	O
is	O
coded	O
using	O
algebraic	B-Algorithm
code-excited	I-Algorithm
linear	I-Algorithm
prediction	I-Algorithm
(	O
ACELP	B-Algorithm
)	O
.	O
</s>
<s>
The	O
complexity	O
of	O
the	O
algorithm	O
is	O
rated	O
at	O
5	O
,	O
using	O
a	O
relative	O
scale	O
where	O
G.711	B-Algorithm
is	O
1	O
and	O
G.729a	B-Algorithm
is	O
15	O
.	O
</s>
<s>
AMR	O
codecs	B-General_Concept
incorporate	O
several	O
patents	O
of	O
Nokia	O
,	O
Ericsson	O
,	O
NTT	O
and	O
VoiceAge	O
,	O
the	O
last	O
one	O
being	O
the	O
License	O
Administrator	O
for	O
the	O
AMR	O
patent	O
pools	O
.	O
</s>
<s>
However	O
,	O
it	O
's	O
very	O
difficult	O
to	O
determine	O
if	O
there	O
were	O
actually	O
any	O
patents	O
in	O
existence	O
for	O
the	O
so-called	O
inventions	O
related	O
to	O
AMR/AMR	O
-WB	O
codecs	B-General_Concept
,	O
since	O
inventors	O
(	O
and	O
their	O
lawyers	O
)	O
do	O
everything	O
they	O
can	O
to	O
hide	O
patents	O
related	O
to	O
AMR/AMR	O
-WB	O
technology	O
.	O
</s>
<s>
Apparently	O
,	O
all	O
these	O
patents	O
are	O
hidden	O
from	O
all	O
other	O
researches	O
and	O
general	O
audience	O
that	O
could	O
perhaps	O
spot	O
prior	O
art	O
in	O
the	O
claimed	O
"	O
inventions	O
"	O
patented	O
by	O
the	O
patent	O
holders	O
of	O
the	O
AMR/AMR	O
-WB	O
codecs	B-General_Concept
.	O
</s>
<s>
In	O
the	O
category	O
of	O
personal	O
computer	O
products	O
,	O
e.g.	O
,	O
media	O
players	O
,	O
the	O
AMR	O
decoder	O
is	O
licensed	O
for	O
free	B-Application
.	O
</s>
<s>
The	O
minimum	O
annual	O
royalty	O
is	O
not	O
applied	O
to	O
licensed	O
products	O
that	O
fall	O
under	O
the	O
category	O
of	O
personal	O
computer	O
products	O
and	O
use	O
only	O
the	O
free	B-Application
decoder	O
.	O
</s>
<s>
Android	B-Application
Used	O
for	O
voice	O
recorder	O
.	O
</s>
<s>
can	O
convert	O
(	O
create	O
)	O
samples	O
,	O
one	O
can	O
use	O
Nokia	O
's	O
conversion	O
tool	O
to	O
create	O
both	O
.amr	B-Algorithm
and	O
.awb	B-Algorithm
files	O
.	O
</s>
