<s>
aptX	B-Algorithm
(	O
apt	O
stands	O
for	O
audio	O
processing	O
technology	O
)	O
is	O
a	O
family	O
of	O
proprietary	B-Application
audio	B-Algorithm
codec	I-Algorithm
compression	O
algorithms	O
owned	O
by	O
Qualcomm	O
,	O
with	O
a	O
heavy	O
emphasis	O
on	O
wireless	O
audio	O
applications	O
.	O
</s>
<s>
The	O
original	O
aptX	B-Algorithm
algorithm	O
was	O
developed	O
in	O
the	O
1980s	O
by	O
Dr.	O
Stephen	O
Smyth	O
as	O
part	O
of	O
his	O
Ph.D.	O
research	O
at	O
Queen	O
's	O
University	O
Belfast	O
School	O
of	O
Electronics	O
,	O
Electrical	O
Engineering	O
and	O
Computer	O
Science	O
;	O
its	O
design	O
is	O
based	O
on	O
time	O
domain	O
ADPCM	B-Algorithm
principles	O
without	O
psychoacoustic	O
auditory	O
masking	O
techniques	O
.	O
</s>
<s>
aptX	B-Algorithm
audio	O
coding	O
was	O
first	O
introduced	O
to	O
the	O
commercial	O
market	O
as	O
a	O
semiconductor	O
product	O
,	O
a	O
custom	O
programmed	O
DSP	B-Architecture
integrated	O
circuit	O
with	O
part	O
name	O
APTX100ED	O
,	O
which	O
was	O
initially	O
adopted	O
by	O
broadcast	B-Operating_System
automation	O
equipment	O
manufacturers	O
who	O
required	O
a	O
means	O
to	O
store	O
CD-quality	O
audio	O
on	O
a	O
computer	O
hard	B-Device
disk	I-Device
drive	I-Device
for	O
automatic	O
playout	O
during	O
a	O
radio	O
show	O
,	O
for	O
example	O
,	O
hence	O
replacing	O
the	O
task	O
of	O
the	O
disc	O
jockey	O
.	O
</s>
<s>
In	O
the	O
early	O
1990s	O
,	O
APT	O
's	O
codecs	O
were	O
used	O
to	O
transfer	O
audio	O
via	O
ISDN	B-Protocol
lines	I-Protocol
by	O
companies	O
such	O
as	O
Disney	O
to	O
check	O
dubbing	O
done	O
in	O
Europe	O
.	O
</s>
<s>
The	O
range	O
of	O
aptX	B-Algorithm
algorithms	O
for	O
real-time	O
audio	O
data	O
compression	O
expanded	O
with	O
intellectual	O
property	O
becoming	O
available	O
in	O
the	O
form	O
of	O
software	O
,	O
firmware	O
and	O
programmable	O
hardware	O
for	O
professional	O
audio	O
,	O
television	O
and	O
radio	O
broadcast	B-Operating_System
,	O
and	O
consumer	O
electronics	O
,	O
especially	O
applications	O
in	O
wireless	O
audio	O
,	O
low	O
latency	O
wireless	O
audio	O
for	O
gaming	O
and	O
video	O
,	O
and	O
audio	O
over	O
IP	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
aptX	B-Algorithm
codec	O
was	O
introduced	O
as	O
an	O
alternative	O
to	O
SBC	B-General_Concept
,	O
the	O
sub-band	B-Algorithm
coding	I-Algorithm
scheme	O
for	O
lossy	B-Algorithm
stereo/mono	O
audio	O
streaming	O
mandated	O
by	O
the	O
Bluetooth	B-Protocol
SIG	O
for	O
the	O
Advanced	O
Audio	O
Distribution	O
Profile	O
(	O
A2DP	O
)	O
of	O
Bluetooth	B-Protocol
,	O
the	O
short-range	O
wireless	B-General_Concept
personal	I-General_Concept
area	I-General_Concept
network	I-General_Concept
standard	O
.	O
</s>
<s>
aptX	B-Algorithm
is	O
supported	O
in	O
high-performance	O
Bluetooth	B-Protocol
peripherals	O
.	O
</s>
<s>
Today	O
,	O
standard	O
aptX	B-Algorithm
and	O
Enhanced	O
aptX	B-Algorithm
(	O
E-aptX	O
)	O
are	O
used	O
in	O
both	O
ISDN	B-Protocol
and	O
IP	O
audio	B-Algorithm
codec	I-Algorithm
hardware	O
from	O
numerous	O
broadcast	B-Operating_System
equipment	O
makers	O
,	O
including	O
APT	O
WorldCast	O
Systems	O
,	O
Tieline	O
Technology	O
,	O
AVT	O
,	O
Harris	O
Corporation	O
,	O
BW	O
Broadcast	B-Operating_System
,	O
Digigram	O
,	O
MAYAH	O
,	O
Prodys	O
,	O
and	O
Qbit	O
.	O
</s>
<s>
An	O
addition	O
to	O
the	O
aptX	B-Algorithm
family	O
in	O
the	O
form	O
of	O
aptX	B-Algorithm
Live	O
,	O
offering	O
up	O
to	O
8:1	O
compression	O
,	O
was	O
introduced	O
in	O
2007	O
;	O
and	O
aptX	B-Algorithm
HD	O
,	O
a	O
lossy	B-Algorithm
,	O
but	O
scalable	O
,	O
adaptive	O
,	O
"	O
near-lossless	O
"	O
quality	O
audio	B-Algorithm
codec	I-Algorithm
was	O
announced	O
in	O
April	O
2009	O
.	O
</s>
<s>
The	O
company	O
split	O
in	O
2009	O
;	O
the	O
broadcast	B-Operating_System
hardware	O
business	O
was	O
acquired	O
by	O
Audemat	O
and	O
became	O
part	O
of	O
what	O
is	O
now	O
WorldCast	O
Systems	O
,	O
and	O
the	O
licensing	O
business	O
became	O
APT	O
Licensing	O
and	O
was	O
acquired	O
by	O
CSR	O
plc	O
in	O
2010	O
.	O
aptX	B-Algorithm
was	O
previously	O
styled	O
apt-X	B-Algorithm
until	O
acquired	O
by	O
CSR	O
in	O
2010	O
.	O
</s>
<s>
+aptX	O
variantsaptX	O
Adaptive	O
product	O
brief	O
with	O
comparison	O
table	O
(	O
linked	O
pdf	O
)	O
SBC	B-General_Concept
aptX	B-Algorithm
aptX	B-Algorithm
LL	O
aptX	B-Algorithm
HD	O
aptX	B-Algorithm
Adaptive	O
Audio	O
CD	O
@	O
279kbit/s	O
@	O
420	O
kbit/s	O
(	O
for	O
reference	O
)	O
misc	O
.	O
</s>
<s>
<	O
2009History	O
of	O
aptX	B-Algorithm
:	O
Sennheiser	O
launched	O
the	O
first	O
ever	O
Bluetooth	B-Protocol
headset	O
with	O
aptX	B-Algorithm
.	O
</s>
<s>
2012Rayson	O
BTM-770G	O
:	O
One	O
of	O
the	O
first	O
products	O
with	O
Qualcomm	O
Chip	O
CSR8670	O
and	O
aptX	B-Algorithm
LL	O
2016	O
2018	O
1980s	O
Trademark	O
–	O
Qualcomm( until	O
August	O
2015	O
:	O
CSR	O
,	O
until	O
July	O
2010	O
:	O
APT	O
Licensing	O
Ltd.	O
,	O
until	O
March	O
2005	O
:	O
Solid	O
State	O
Logic	O
)	O
–	O
Related	O
patents	O
J.B.	O
Rault	O
,	O
Y.F.	O
</s>
<s>
Veldhuis	O
,	O
"	O
Digital	O
transmission	O
system	O
using	O
subband	B-Algorithm
coding	I-Algorithm
of	O
a	O
digital	O
signal	O
"	O
,	O
Publication	O
number	O
:	O
(	O
expired	O
)	O
S.M.F.	O
</s>
<s>
Smyth	O
,	O
"	O
Method	O
and	O
apparatus	O
for	O
electrical	O
signal	O
coding	O
"	O
,	O
Publication	O
number	O
:	O
(	O
revoked	O
)	O
aptX	B-Algorithm
,	O
J.J.	O
Lazzeroni	O
,	O
M.K.	O
</s>
<s>
Kingston	O
,	O
"	O
Simultaneous	O
voice	O
and	O
audio	O
traffic	O
between	O
two	O
devices	O
on	O
a	O
wireless	O
personal-area	B-General_Concept
network	I-General_Concept
"	O
,	O
Publication	O
number	O
:	O
(	O
expired	O
)	O
aptX	B-Algorithm
?	O
</s>
<s>
–	O
Free	B-Application
implementations	I-Application
BlueZ	O
libsbcPulseAudio	O
,	O
PipeWire	B-Application
FFmpeg	B-Library
,	O
libopenaptx	O
,	O
PulseAudio	B-Library
,	O
PipeWire	B-Application
FFmpeg	B-Library
,	O
libopenaptx	O
,	O
PipeWire	B-Application
FFmpeg	B-Library
,	O
libopenaptx	O
,	O
PulseAudio	B-Library
,	O
PipeWire	B-Application
N/A	O
–	O
Proprietary	B-Application
implementations	I-Application
Multiple	O
Qualcomm	O
libaptXIntegration	O
of	O
the	O
aptX	B-Algorithm
and	O
aptX-HD	O
codecs	O
for	O
A2DP	O
source	O
,	O
Android	O
Open	O
Source	O
Project	O
,	O
January	O
4	O
,	O
2017	O
None	O
Qualcomm	O
libaptXHD	O
?	O
</s>
<s>
≈	O
80	O
ms	O
–	O
Software	O
transmitter	O
latency	O
(	O
most	O
phones	O
)	O
200	O
–	O
500	O
msdepending	O
on	O
the	O
transmitting	O
device	O
–	O
Backwards	O
compatible	O
with	O
–	O
SBC	B-General_Concept
SBC	B-General_Concept
,	O
aptX	B-Algorithm
SBC	B-General_Concept
,	O
aptX	B-Algorithm
SBC	B-General_Concept
,	O
aptX	B-Algorithm
,	O
aptX	B-Algorithm
HD	O
?	O
</s>
<s>
The	O
aptX	B-Algorithm
audio	B-Algorithm
codec	I-Algorithm
is	O
used	O
for	O
consumer	O
and	O
automotive	O
wireless	O
audio	O
applications	O
,	O
notably	O
the	O
real-time	O
streaming	O
of	O
lossy	B-Algorithm
stereo	O
audio	O
over	O
the	O
Bluetooth	B-Protocol
A2DP	O
connection/pairing	O
between	O
a	O
"	O
source	O
"	O
device	O
(	O
such	O
as	O
a	O
smartphone	O
,	O
tablet	O
or	O
laptop	O
)	O
and	O
a	O
"	O
sink	O
"	O
accessory	O
(	O
e.g.	O
</s>
<s>
a	O
Bluetooth	B-Protocol
stereo	O
speaker	O
,	O
headset	O
or	O
headphones	O
)	O
.	O
</s>
<s>
The	O
technology	O
must	O
be	O
incorporated	O
in	O
both	O
transmitter	O
and	O
receiver	O
to	O
derive	O
the	O
sonic	O
benefits	O
of	O
aptX	B-Algorithm
audio	O
coding	O
over	O
the	O
default	O
sub-band	B-Algorithm
coding	I-Algorithm
(	O
SBC	B-General_Concept
)	O
mandated	O
by	O
the	O
Bluetooth	B-Protocol
standard	O
.	O
</s>
<s>
Products	O
bearing	O
the	O
CSR	O
aptX	B-Algorithm
logo	O
are	O
certified	O
for	O
interoperability	O
with	O
each	O
other	O
.	O
</s>
<s>
Enhanced	O
aptX	B-Algorithm
provides	O
coding	O
at	O
4:1	O
compression	O
ratios	O
for	O
professional	O
audio	O
broadcast	B-Operating_System
applications	O
and	O
is	O
suitable	O
for	O
AM	O
,	O
FM	O
,	O
DAB	O
,	O
HD	O
Radio	O
and	O
5.1	O
.	O
</s>
<s>
Enhanced	O
aptX	B-Algorithm
can	O
handle	O
up	O
to	O
4	O
stereo	O
pairs	O
of	O
AES3	O
audio	O
and	O
compress	O
to	O
1	O
AES3	O
stream	O
for	O
transmit	O
.	O
</s>
<s>
Enhanced	O
aptX	B-Algorithm
supports	O
bit-depths	O
of	O
16	O
,	O
20	O
or	O
24	O
bit	O
.	O
</s>
<s>
For	O
audio	O
sampled	O
at	O
48kHz	O
,	O
the	O
bit-rate	O
for	O
E-aptX	O
is	O
384	O
kbit/s	O
(	O
dual	O
channel	O
)	O
,	O
768	O
kbit/s	O
(	O
quad	O
channel	O
)	O
,	O
1024	O
kbit/s	O
(	O
5.1-channel	O
)	O
,	O
and	O
1280	O
kbit/s	O
(	O
5.1	O
channels	O
plus	O
stereo	O
)	O
.	O
</s>
<s>
aptX	B-Algorithm
Live	O
is	O
a	O
low-complexity	O
audio	B-Algorithm
codec	I-Algorithm
that	O
is	O
specifically	O
designed	O
to	O
maximise	O
digital	O
wireless	B-Device
microphone	I-Device
channel	O
density	O
in	O
bandwidth-constrained	O
scenarios	O
,	O
such	O
as	O
live	O
performance	O
(	O
a.k.a.	O
</s>
<s>
Programme	O
Making	O
and	O
Special	O
Events	O
)	O
,	O
where	O
the	O
spectrum-efficiency	O
of	O
radio-based	O
devices	O
(	O
wireless	B-Device
microphones	I-Device
,	O
in-ear	O
monitoring	O
,	O
talk-back	O
systems	O
)	O
is	O
becoming	O
a	O
prime	O
operational	O
consideration	O
.	O
</s>
<s>
aptX	B-Algorithm
Live	O
offers	O
up	O
to	O
8:1	O
compression	O
of	O
24-bit	O
resolution	O
digital	O
audio	O
streams	O
while	O
maintaining	O
acoustic	O
integrity	O
(	O
approx	O
.	O
</s>
<s>
In	O
addition	O
,	O
aptX	B-Algorithm
Live	O
also	O
features	O
techniques	O
that	O
aid	O
connection	O
in	O
situations	O
where	O
the	O
bit	O
error	O
rate	O
(	O
BER	O
)	O
is	O
excessively	O
high	O
.	O
</s>
<s>
aptX	B-Algorithm
LL	O
or	O
aptX	B-Algorithm
Low	O
Latency	O
is	O
intended	O
for	O
video	O
and	O
gaming	O
applications	O
requiring	O
comfortable	O
audio-video	O
synchronization	O
whenever	O
the	O
stereo	O
audio	O
is	O
transmitted	O
over	O
short-range	O
radio	O
to	O
the	O
listener(s )	O
using	O
the	O
Bluetooth	B-Protocol
A2DP	O
audio	O
profile	O
standard	O
.	O
</s>
<s>
The	O
technology	O
offers	O
an	O
end-to-end	O
latency	O
of	O
32ms	O
over	O
Bluetooth	B-Protocol
.	O
</s>
<s>
By	O
comparison	O
,	O
the	O
latency	O
of	O
standard	O
Bluetooth	B-Protocol
stereo	O
varies	O
greatly	O
depending	O
on	O
the	O
system	O
implementation	O
and	O
buffering	O
.	O
</s>
<s>
Solutions	O
are	O
available	O
that	O
use	O
standard	O
SBC	B-General_Concept
encoding/decoding	O
that	O
achieve	O
end-to-end	O
latency	O
of	O
less	O
than	O
40ms	O
.	O
</s>
<s>
The	O
recommended	O
latency	O
for	O
audio-to-video	B-Protocol
synchronization	I-Protocol
in	O
broadcast	B-Operating_System
television	O
is	O
within	O
+40ms	O
and	O
−60ms	O
(	O
audio	O
before/after	O
video	O
,	O
respectively	O
)	O
.	O
</s>
<s>
However	O
,	O
AptX	B-Algorithm
Low	O
Latency	O
requires	O
a	O
dedicated	O
,	O
wireless	O
antenna	O
,	O
so	O
it	O
did	O
not	O
achieve	O
much	O
adoption	O
in	O
smartphones	O
and	O
was	O
retired	O
by	O
Qualcomm	O
in	O
favor	O
of	O
aptX	B-Algorithm
Adaptive	O
.	O
</s>
<s>
aptX	B-Algorithm
HD	O
or	O
aptX	B-Algorithm
High	O
Definition	O
has	O
bit-rate	O
of	O
576	O
kbit/s	O
.	O
</s>
<s>
Unlike	O
the	O
name	O
suggests	O
,	O
the	O
codec	O
is	O
still	O
considered	O
lossy	B-Algorithm
;	O
however	O
,	O
it	O
permits	O
a	O
"	O
hybrid	O
"	O
coding	O
scheme	O
for	O
applications	O
where	O
average	O
or	O
peak	O
compressed	O
data	O
rates	O
must	O
be	O
capped	O
at	O
a	O
constrained	O
level	O
.	O
</s>
<s>
Its	O
main	O
competitors	O
are	O
LDAC	B-Algorithm
codec	I-Algorithm
developed	O
by	O
Sony	O
and	O
LHDC	B-Algorithm
.	O
</s>
<s>
Another	O
scalable	O
parameter	O
within	O
aptX	B-Algorithm
HD	O
is	O
coding	O
latency	O
.	O
</s>
<s>
The	O
latency	O
of	O
the	O
aptX	B-Algorithm
HD	O
codec	O
can	O
be	O
scaled	O
to	O
as	O
low	O
as	O
1	O
ms	O
for	O
48kHz	O
sampled	O
audio	O
,	O
depending	O
on	O
the	O
settings	O
of	O
other	O
configurable	O
parameters	O
.	O
</s>
<s>
aptX	B-Algorithm
HD	O
performs	O
particularly	O
well	O
against	O
other	O
lossless	O
codecs	O
when	O
the	O
coding	O
latency	O
is	O
constrained	O
to	O
be	O
small	O
,	O
such	O
as	O
5	O
ms	O
or	O
less	O
,	O
making	O
it	O
particularly	O
appropriate	O
for	O
delay-sensitive	O
interactive	O
audio	O
applications	O
.	O
</s>
<s>
Many	O
lossless	O
codecs	O
possess	O
the	O
benefit	O
of	O
a	O
low	O
computational	O
overhead	O
compared	O
to	O
well-known	O
lossy	B-Algorithm
codecs	O
,	O
such	O
as	O
MP3	B-Application
and	O
AAC	B-Application
.	O
</s>
<s>
aptX	B-Algorithm
HD	O
promotes	O
low	O
computational	O
overhead	O
by	O
dynamically	O
selecting	O
the	O
simplest	O
coding	O
functions	O
for	O
each	O
short	O
segment	O
of	O
audio	O
whilst	O
complying	O
with	O
other	O
operational	O
constraints	O
,	O
such	O
as	O
levels	O
of	O
compression	O
and	O
coding	O
delay	O
.	O
</s>
<s>
Depending	O
on	O
the	O
settings	O
of	O
other	O
scalable	O
parameters	O
,	O
aptX	B-Algorithm
HD	O
can	O
encode	O
a	O
48kHz	O
16-bit	O
stereo	O
audio	O
stream	O
using	O
only	O
10	O
MIPS	O
on	O
a	O
modern	O
RISC	B-Architecture
processor	I-Architecture
with	O
signal	O
processing	O
extensions	O
.	O
</s>
<s>
aptX	B-Algorithm
Adaptive	O
is	O
a	O
next-generation	O
dynamically	O
adjustable	O
audio	B-Algorithm
codec	I-Algorithm
intended	O
for	O
premium	O
audio	O
quality	O
and	O
low-latency	O
.	O
</s>
<s>
aptX	B-Algorithm
Adaptive	O
’s	O
bitrate	O
scales	O
dynamically	O
between	O
279	O
kbps	O
and	O
420	O
kbps	O
.	O
</s>
<s>
This	O
allows	O
aptX	B-Algorithm
Adaptive	O
at	O
279	O
kbps	O
and	O
420	O
kbps	O
to	O
produce	O
the	O
same	O
sound	O
quality	O
as	O
aptX	B-Algorithm
at	O
352	O
kbps	O
and	O
aptX	B-Algorithm
HD	O
at	O
576	O
kbps	O
.	O
</s>
<s>
aptX	B-Algorithm
Adaptive	O
supports	O
16	O
and	O
24	O
bit-depths	O
at	O
44.1	O
,	O
48	O
,	O
and	O
96kHz	O
sample	O
rates	O
.	O
</s>
<s>
For	O
example	O
B&O	O
H95	O
only	O
support	O
48	O
KHz	O
at	O
max	O
even	O
with	O
AptX	B-Algorithm
Adaptive	O
support	O
.	O
</s>
<s>
Hardware	O
aptX	B-Algorithm
Adaptive	O
has	O
end-to-end	O
latency	O
of	O
80	O
ms	O
,	O
but	O
most	O
phones	O
are	O
using	O
a	O
software	O
transmitter	O
-	O
which	O
does	O
not	O
have	O
any	O
latency	O
advantages	O
over	O
other	O
codecs	O
.	O
</s>
<s>
aptX	B-Algorithm
Adaptive	O
is	O
also	O
backward	O
compatible	O
with	O
older	O
aptX	B-Algorithm
and	O
aptX	B-Algorithm
HD	O
codecs	O
,	O
but	O
not	O
with	O
aptX	B-Algorithm
LL	O
.	O
</s>
<s>
aptX	B-Algorithm
Voice	O
is	O
a	O
new	O
feature	O
of	O
aptX	B-Algorithm
Adaptive	O
,	O
and	O
is	O
designed	O
to	O
significantly	O
improve	O
the	O
quality	O
of	O
voice	O
for	O
those	O
using	O
Bluetooth	B-Protocol
accessories	O
to	O
make	O
voice	O
calls	O
.	O
</s>
<s>
It	O
does	O
this	O
by	O
delivering	O
32kHz	O
voice	O
call	O
quality	O
within	O
the	O
Bluetooth	B-Protocol
Hands-Free	O
Profile	O
.	O
</s>
<s>
The	O
example	O
CD-quality	O
16-bit	O
44kHz	O
(	O
up	O
to	O
22kHz	O
signal	O
bandwidth	O
)	O
stream	O
is	O
divided	O
by	O
two	O
layers	O
of	O
64-tap	O
QMF	O
(	O
Quadrature	O
mirror	O
filter	O
)	O
into	O
four	O
16-bit	O
subbands	B-Algorithm
of	O
11kHz	O
(	O
up	O
to	O
5.5kHz	O
signal	O
bandwidth	O
each	O
)	O
.	O
</s>
<s>
Reduced	O
variance	O
is	O
generally	O
expected	O
to	O
be	O
found	O
in	O
higher	O
bands	O
compared	O
to	O
lower	O
bands	O
,	O
thus	O
ADPCM	B-Algorithm
is	O
employed	O
to	O
allocate	O
bits	O
optimally	O
.	O
</s>
<s>
Each	O
band	O
is	O
coded	O
with	O
ADPCM	B-Algorithm
using	O
bit	O
allocation	O
of	O
8	O
bits	O
for	O
band	O
1	O
(	O
0-5.5kHz	O
spectrum	O
)	O
,	O
4	O
bits	O
for	O
band	O
2	O
(	O
5.5	O
–	O
11kHz	O
)	O
,	O
2	O
bits	O
each	O
for	O
bands	O
3	O
and	O
4	O
(	O
11-16.5kHz	O
and	O
16.5	O
–	O
22kHz	O
)	O
.	O
</s>
<s>
A	O
future	O
modification	O
is	O
considered	O
with	O
adaptive	O
bit	O
reallocation	O
based	O
on	O
variance	O
analysis	O
of	O
each	O
subband	B-Algorithm
,	O
for	O
example	O
9	O
,	O
2	O
,	O
3	O
,	O
2	O
etc	O
.	O
</s>
<s>
Optionally	O
(	O
adds	O
a	O
small	O
delay	O
)	O
a	O
short-term	O
RMSE	B-General_Concept
analyzer	O
is	O
used	O
to	O
reduce	O
dynamic	O
range	O
,	O
and	O
thus	O
allocate	O
bits	O
more	O
effectively	O
during	O
quiet	O
passages	O
(	O
i.e.	O
</s>
<s>
lossy	B-Algorithm
format	O
)	O
.	O
</s>
<s>
For	O
a	O
stereo	O
signal	O
,	O
a	O
standard	O
PCM	O
1.4-Mbit	O
stream	O
is	O
converted	O
into	O
352	O
Kbit/sec	O
aptX	B-Algorithm
stream	O
.	O
</s>
<s>
The	O
main	O
reasoning	O
is	O
that	O
signal	O
variation	O
is	O
reduced	O
at	O
higher	O
frequencies	O
,	O
which	O
makes	O
it	O
amenable	O
to	O
coding	O
with	O
codecs	O
like	O
ADPCM	B-Algorithm
.	O
</s>
