<s>
Adaptive	B-Algorithm
differential	I-Algorithm
pulse-code	I-Algorithm
modulation	I-Algorithm
(	O
ADPCM	B-Algorithm
)	O
is	O
a	O
variant	O
of	O
differential	B-General_Concept
pulse-code	I-General_Concept
modulation	I-General_Concept
(	O
DPCM	B-General_Concept
)	O
that	O
varies	O
the	O
size	O
of	O
the	O
quantization	O
step	O
,	O
to	O
allow	O
further	O
reduction	O
of	O
the	O
required	O
data	O
bandwidth	O
for	O
a	O
given	O
signal-to-noise	O
ratio	O
.	O
</s>
<s>
Typically	O
,	O
the	O
adaptation	O
to	O
signal	O
statistics	O
in	O
ADPCM	B-Algorithm
consists	O
simply	O
of	O
an	O
adaptive	O
scale	O
factor	O
before	O
quantizing	O
the	O
difference	O
in	O
the	O
DPCM	B-General_Concept
encoder	O
.	O
</s>
<s>
ADPCM	B-Algorithm
was	O
developed	O
for	O
speech	B-Application
coding	I-Application
by	O
P	O
.	O
Cummiskey	O
,	O
Nikil	O
S	O
.	O
Jayant	O
and	O
James	O
L	O
.	O
Flanagan	O
at	O
Bell	O
Labs	O
in	O
1973	O
.	O
</s>
<s>
The	O
default	O
signal	O
compression	O
encoding	O
on	O
a	O
DS0	O
is	O
either	O
μ-law	B-Algorithm
(	O
mu-law	B-Algorithm
)	O
PCM	B-Algorithm
(	O
North	O
America	O
and	O
Japan	O
)	O
or	O
A-law	B-Algorithm
PCM	B-Algorithm
(	O
Europe	O
and	O
most	O
of	O
the	O
rest	O
of	O
the	O
world	O
)	O
.	O
</s>
<s>
These	O
are	O
logarithmic	O
compression	O
systems	O
where	O
a	O
13	O
-	O
or	O
14-bit	O
linear	B-Algorithm
PCM	I-Algorithm
sample	O
number	O
is	O
mapped	O
into	O
an	O
8-bit	O
value	O
.	O
</s>
<s>
This	O
system	O
is	O
described	O
by	O
international	O
standard	O
G.711	B-Algorithm
.	O
</s>
<s>
An	O
ADPCM	B-Algorithm
algorithm	O
is	O
used	O
to	O
map	O
a	O
series	O
of	O
8-bit	O
μ-law	B-Algorithm
(	O
or	O
a-law	B-Algorithm
)	O
PCM	B-Algorithm
samples	O
into	O
a	O
series	O
of	O
4-bit	O
ADPCM	B-Algorithm
samples	O
.	O
</s>
<s>
The	O
technique	O
is	O
detailed	O
in	O
the	O
G.726	B-Algorithm
standard	O
.	O
</s>
<s>
ADPCM	B-Algorithm
techniques	O
are	O
used	O
in	O
voice	B-Application
over	I-Application
IP	I-Application
communications	O
.	O
</s>
<s>
In	O
the	O
early	O
1990s	O
,	O
ADPCM	B-Algorithm
was	O
also	O
used	O
by	O
Interactive	O
Multimedia	O
Association	O
to	O
develop	O
the	O
legacy	O
audio	O
codecs	B-General_Concept
ADPCM	B-Algorithm
DVI	O
,	O
IMA	B-Algorithm
ADPCM	I-Algorithm
,	O
and	O
DVI4	O
.	O
</s>
<s>
G.722	B-Algorithm
is	O
an	O
ITU-T	O
standard	O
wideband	O
speech	B-Application
codec	I-Application
operating	O
at	O
48	O
,	O
56	O
and	O
64kbit/s	O
,	O
based	O
on	O
subband	B-Algorithm
coding	I-Algorithm
with	O
two	O
channels	O
and	O
ADPCM	B-Algorithm
coding	O
of	O
each	O
.	O
</s>
<s>
Before	O
the	O
digitization	O
process	O
,	O
it	O
catches	O
the	O
analog	O
signal	O
and	O
divides	O
it	O
in	O
frequency	O
bands	O
with	O
quadrature	O
mirror	O
filters	O
(	O
QMF	O
)	O
to	O
get	O
two	O
subbands	B-Algorithm
of	O
the	O
signal	O
.	O
</s>
<s>
When	O
the	O
ADPCM	B-Algorithm
bitstream	O
of	O
each	O
subband	B-Algorithm
is	O
obtained	O
,	O
the	O
results	O
are	O
multiplexed	O
,	O
and	O
the	O
next	O
step	O
is	O
storage	O
or	O
transmission	O
of	O
the	O
data	O
.	O
</s>
<s>
The	O
decoder	O
has	O
to	O
perform	O
the	O
reverse	O
process	O
,	O
that	O
is	O
,	O
demultiplex	O
and	O
decode	O
each	O
subband	B-Algorithm
of	O
the	O
bitstream	O
and	O
recombine	O
them	O
.	O
</s>
<s>
Referring	O
to	O
the	O
coding	O
process	O
,	O
in	O
some	O
applications	O
as	O
voice	O
coding	O
,	O
the	O
subband	B-Algorithm
that	O
includes	O
the	O
voice	O
is	O
coded	O
with	O
more	O
bits	O
than	O
the	O
others	O
.	O
</s>
<s>
The	O
Windows	O
Sound	O
System	O
supported	O
ADPCM	B-Algorithm
in	O
WAV	O
files	O
.	O
</s>
<s>
The	O
FFmpeg	B-Library
audio	O
codecs	B-General_Concept
supporting	O
ADPCM	B-Algorithm
are	O
adpcm_ima_qt	O
,	O
adpcm_ima_wav	O
,	O
adpcm_ms	O
,	O
adpcm_swf	O
and	O
adpcm_yamaha	O
.	O
</s>
<s>
The	O
Nintendo	B-Application
Gamecube	I-Application
's	O
onboard	O
DSP	O
supports	O
ADPCM	B-Algorithm
encoding	O
on	O
64	O
simultaneous	O
audio	O
channels	O
.	O
</s>
