<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
(	O
WMA	B-Application
)	O
is	O
a	O
series	O
of	O
audio	B-Algorithm
codecs	I-Algorithm
and	O
their	O
corresponding	O
audio	O
coding	O
formats	O
developed	O
by	O
Microsoft	O
.	O
</s>
<s>
It	O
is	O
a	O
proprietary	B-Application
technology	I-Application
that	O
forms	O
part	O
of	O
the	O
Windows	B-Device
Media	I-Device
framework	O
.	O
</s>
<s>
WMA	B-Application
consists	O
of	O
four	O
distinct	O
codecs	B-General_Concept
.	O
</s>
<s>
The	O
original	O
WMA	B-Application
codec	B-General_Concept
,	O
known	O
simply	O
as	O
WMA	B-Application
,	O
was	O
conceived	O
as	O
a	O
competitor	O
to	O
the	O
popular	O
MP3	B-Application
and	O
RealAudio	B-Algorithm
codecs	B-General_Concept
.	O
</s>
<s>
WMA	B-Application
Pro	O
,	O
a	O
newer	O
and	O
more	O
advanced	O
codec	B-General_Concept
,	O
supports	O
multichannel	O
and	O
high	O
resolution	O
audio	O
.	O
</s>
<s>
A	O
lossless	B-Algorithm
codec	I-Algorithm
,	O
WMA	B-Application
Lossless	B-Algorithm
,	O
compresses	O
audio	O
data	O
without	O
loss	O
of	O
audio	O
fidelity	O
(	O
the	O
regular	O
WMA	B-Application
format	O
is	O
lossy	B-Algorithm
)	O
.	O
</s>
<s>
WMA	B-Application
Voice	O
,	O
targeted	O
at	O
voice	O
content	O
,	O
applies	O
compression	O
using	O
a	O
range	O
of	O
low	O
bit	O
rates	O
.	O
</s>
<s>
Microsoft	O
has	O
also	O
developed	O
a	O
digital	O
container	O
format	O
called	O
Advanced	B-Application
Systems	I-Application
Format	I-Application
to	O
store	O
audio	O
encoded	O
by	O
WMA	B-Application
.	O
</s>
<s>
The	O
first	O
WMA	B-Application
codec	B-General_Concept
was	O
based	O
on	O
earlier	O
work	O
by	O
Henrique	O
Malvar	O
and	O
his	O
team	O
which	O
was	O
transferred	O
to	O
the	O
Windows	B-Device
Media	I-Device
team	O
at	O
Microsoft	O
.	O
</s>
<s>
Malvar	O
was	O
a	O
senior	O
researcher	O
and	O
manager	O
of	O
the	O
Signal	O
Processing	O
Group	O
at	O
Microsoft	O
Research	O
,	O
whose	O
team	O
worked	O
on	O
the	O
MSAudio	B-Application
project	O
.	O
</s>
<s>
The	O
first	O
finalized	O
codec	B-General_Concept
was	O
initially	O
referred	O
to	O
as	O
MSAudio	B-Application
4.0	O
.	O
</s>
<s>
It	O
was	O
later	O
officially	O
released	O
as	O
Windows	B-Application
Media	I-Application
Audio	I-Application
,	O
as	O
part	O
of	O
Windows	B-Device
Media	I-Device
Technologies	O
4.0	O
.	O
</s>
<s>
Microsoft	O
claimed	O
that	O
WMA	B-Application
could	O
produce	O
files	O
that	O
were	O
half	O
the	O
size	O
of	O
equivalent-quality	O
MP3	B-Application
files	I-Application
;	O
Microsoft	O
also	O
claimed	O
that	O
WMA	B-Application
delivered	O
"	O
near	O
CD-quality	O
"	O
audio	O
at	O
64kbit/s	O
.	O
</s>
<s>
The	O
former	O
claim	O
however	O
was	O
rejected	O
by	O
some	O
audiophiles	O
and	O
both	O
claims	O
have	O
been	O
refuted	O
through	O
publicly-available	O
codec	B-General_Concept
listening	O
tests	O
.	O
</s>
<s>
RealNetworks	O
also	O
challenged	O
Microsoft	O
's	O
claims	O
regarding	O
WMA	B-Application
's	O
superior	O
audio	O
quality	O
compared	O
to	O
RealAudio	B-Algorithm
.	O
</s>
<s>
Newer	O
versions	O
of	O
WMA	B-Application
became	O
available	O
:	O
Windows	B-Application
Media	I-Application
Audio	I-Application
2	O
in	O
1999	O
,	O
Windows	B-Application
Media	I-Application
Audio	I-Application
7	O
in	O
2000	O
,	O
Windows	B-Application
Media	I-Application
Audio	I-Application
8	O
in	O
2001	O
,	O
and	O
Windows	B-Application
Media	I-Application
Audio	I-Application
9	O
in	O
2003	O
.	O
</s>
<s>
Microsoft	O
first	O
announced	O
its	O
plans	O
to	O
license	O
WMA	B-Application
technology	O
to	O
third	O
parties	O
in	O
1999	O
.	O
</s>
<s>
Prior	O
to	O
Windows	B-Application
XP	I-Application
,	O
WMA	B-Application
files	I-Application
were	O
primarily	O
streamed	O
using	O
the	O
Windows	B-Device
Media	I-Device
Source	O
Filter	O
(	O
DirectShow	B-Library
codec	B-General_Concept
)	O
,	O
later	O
being	O
removed	O
in	O
Windows	O
Vista	O
with	O
the	O
addition	O
of	O
Media	O
Foundation	O
.	O
</s>
<s>
Although	O
earlier	O
versions	O
of	O
Windows	B-Device
Media	I-Device
Player	I-Device
played	O
WMA	B-Application
files	I-Application
,	O
support	O
for	O
WMA	B-Application
file	I-Application
creation	O
was	O
not	O
added	O
until	O
the	O
seventh	O
version	O
.	O
</s>
<s>
In	O
2003	O
,	O
Microsoft	O
released	O
new	O
audio	B-Algorithm
codecs	I-Algorithm
that	O
were	O
not	O
compatible	O
with	O
the	O
original	O
WMA	B-Application
codec	B-General_Concept
.	O
</s>
<s>
These	O
codecs	B-General_Concept
were	O
Windows	B-Application
Media	I-Application
Audio	I-Application
9	O
Professional	O
,	O
Windows	B-Application
Media	I-Application
Audio	I-Application
9	O
Lossless	B-Algorithm
,	O
and	O
Windows	B-Application
Media	I-Application
Audio	I-Application
9	O
Voice	O
.	O
</s>
<s>
All	O
versions	O
of	O
WMA	B-Application
released	O
since	O
version	O
9.0namely	O
9.1	O
,	O
9.2	O
,	O
and	O
10have	O
been	O
backwards	O
compatible	O
with	O
the	O
original	O
v9	O
decoder	O
and	O
are	O
therefore	O
not	O
considered	O
separate	O
codecs	B-General_Concept
.	O
</s>
<s>
The	O
sole	O
exception	O
to	O
this	O
is	O
the	O
WMA	B-Application
10	O
Professional	O
codec	B-General_Concept
whose	O
Low	O
Bit	O
Rate	O
(	O
LBR	O
)	O
mode	O
is	O
only	O
backwards	O
compatible	O
with	O
the	O
older	O
WMA	B-Application
Professional	O
decoders	O
at	O
a	O
half	O
sampling	O
rate	O
(	O
similar	O
to	O
how	O
HE-AAC	O
is	O
backwards	O
compatible	O
with	O
AAC-LC	B-Application
)	O
.	O
</s>
<s>
Full	O
fidelity	O
decoding	O
of	O
WMA	B-Application
10	O
Professional	O
LBR	O
bitstreams	O
requires	O
a	O
WMA	B-Application
version	O
10	O
or	O
newer	O
decoder	O
.	O
</s>
<s>
A	O
WMA	B-Application
file	I-Application
is	O
in	O
most	O
circumstances	O
contained	O
in	O
the	O
Advanced	B-Application
Systems	I-Application
Format	I-Application
(	O
ASF	O
)	O
,	O
a	O
proprietary	B-Application
Microsoft	O
container	O
format	O
for	O
digital	O
audio	O
or	O
digital	O
video	O
.	O
</s>
<s>
The	O
ASF	O
container	O
format	O
specifies	O
how	O
metadata	O
about	O
the	O
file	O
is	O
to	O
be	O
encoded	O
,	O
similar	O
to	O
the	O
ID3	O
tags	O
used	O
by	O
MP3	B-Application
files	I-Application
.	O
</s>
<s>
This	O
container	O
can	O
optionally	O
support	O
digital	O
rights	O
management	O
(	O
DRM	O
)	O
using	O
a	O
combination	O
of	O
elliptic	O
curve	O
cryptography	O
key	O
exchange	O
,	O
DES	B-Algorithm
block	O
cipher	O
,	O
a	O
custom	O
block	O
cipher	O
,	O
RC4	B-Algorithm
stream	O
cipher	O
and	O
the	O
SHA-1	B-Algorithm
hashing	O
function	O
.	O
</s>
<s>
See	O
Windows	B-Device
Media	I-Device
DRM	O
for	O
further	O
information	O
.	O
</s>
<s>
Since	O
2008	O
Microsoft	O
has	O
also	O
been	O
using	O
WMA	B-Application
Professional	O
in	O
its	O
Protected	O
Interoperable	O
File	O
Format	O
(	O
PIFF	O
)	O
based	O
on	O
the	O
ISO	O
Base	O
Media	O
File	O
Format	O
and	O
most	O
commonly	O
used	O
for	O
Smooth	O
Streaming	O
,	O
a	O
form	O
of	O
adaptive	O
bitrate	O
streaming	O
over	O
HTTP	O
.	O
</s>
<s>
Related	O
industry	O
standards	O
such	O
as	O
DECE	O
UltraViolet	O
and	O
MPEG-DASH	B-Protocol
have	O
not	O
standardized	O
WMA	B-Application
as	O
a	O
supported	O
audio	B-Algorithm
codec	I-Algorithm
,	O
deciding	O
in	O
favor	O
of	O
the	O
more	O
industry-prevalent	O
MPEG	O
and	O
Dolby	O
audio	B-Algorithm
codecs	I-Algorithm
.	O
</s>
<s>
Each	O
WMA	B-Application
file	I-Application
features	O
a	O
single	O
audio	O
track	O
in	O
one	O
of	O
the	O
four	O
sub-formats	O
:	O
WMA	B-Application
,	O
WMA	B-Application
Pro	O
,	O
WMA	B-Application
Lossless	B-Algorithm
,	O
or	O
WMA	B-Application
Voice	O
.	O
</s>
<s>
These	O
formats	O
are	O
implemented	O
differently	O
from	O
one	O
another	O
,	O
such	O
that	O
they	O
are	O
technically	O
distinct	O
and	O
mutually	O
incompatible	O
;	O
that	O
is	O
to	O
say	O
,	O
a	O
device	O
or	O
software	O
compatible	O
with	O
one	O
sub-format	O
does	O
not	O
therefore	O
automatically	O
support	O
any	O
of	O
the	O
other	O
codecs	B-General_Concept
.	O
</s>
<s>
Each	O
codec	B-General_Concept
is	O
further	O
explained	O
below	O
.	O
</s>
<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
(	O
WMA	B-Application
)	O
is	O
the	O
most	O
common	O
codec	B-General_Concept
of	O
the	O
four	O
WMA	B-Application
codecs	B-General_Concept
.	O
</s>
<s>
The	O
colloquial	O
usage	O
of	O
the	O
term	O
WMA	B-Application
,	O
especially	O
in	O
marketing	O
materials	O
and	O
device	O
specifications	O
,	O
usually	O
refers	O
to	O
this	O
codec	B-General_Concept
only	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
the	O
codec	B-General_Concept
released	O
in	O
1999	O
is	O
regarded	O
as	O
WMA	B-Application
1	O
.	O
</s>
<s>
In	O
the	O
same	O
year	O
,	O
the	O
bit	O
stream	O
syntax	O
,	O
or	O
compression	B-General_Concept
algorithm	I-General_Concept
,	O
was	O
altered	O
in	O
minor	O
ways	O
and	O
became	O
WMA	B-Application
2	O
.	O
</s>
<s>
Since	O
then	O
,	O
newer	O
versions	O
of	O
the	O
codec	B-General_Concept
have	O
been	O
released	O
,	O
but	O
the	O
decoding	O
process	O
remained	O
the	O
same	O
,	O
ensuring	O
compatibility	O
between	O
codec	B-General_Concept
versions	O
.	O
</s>
<s>
WMA	B-Application
is	O
a	O
lossy	B-Algorithm
audio	B-Algorithm
codec	I-Algorithm
based	O
on	O
the	O
study	O
of	O
psychoacoustics	O
.	O
</s>
<s>
WMA	B-Application
can	O
encode	O
audio	O
signals	O
sampled	O
at	O
up	O
to	O
48kHz	O
with	O
up	O
to	O
two	O
discrete	O
channels	O
(	O
stereo	O
)	O
.	O
</s>
<s>
WMA	B-Application
9	O
introduced	O
variable	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
(	O
VBR	O
)	O
and	O
average	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
(	O
ABR	O
)	O
coding	B-General_Concept
techniques	I-General_Concept
into	O
the	O
MS	O
encoder	O
although	O
both	O
were	O
technically	O
supported	O
by	O
the	O
original	O
format	O
.	O
</s>
<s>
WMA	B-Application
9.1	O
also	O
added	O
support	O
for	O
low-delay	O
audio	O
,	O
which	O
reduces	O
latency	O
for	O
encoding	O
and	O
decoding	O
.	O
</s>
<s>
Fundamentally	O
,	O
WMA	B-Application
is	O
a	O
transform	O
coder	O
based	O
on	O
modified	O
discrete	O
cosine	O
transform	O
(	O
MDCT	O
)	O
,	O
somewhat	O
similar	O
to	O
AAC	B-Application
,	O
Cook	B-Algorithm
and	O
Vorbis	B-Algorithm
.	O
</s>
<s>
The	O
bit	O
stream	O
of	O
WMA	B-Application
is	O
composed	O
of	O
superframes	O
,	O
each	O
containing	O
1	O
or	O
more	O
frames	O
of	O
2048	O
samples	O
.	O
</s>
<s>
Finally	O
,	O
the	O
floating	B-Algorithm
point	I-Algorithm
samples	O
are	O
decomposed	O
into	O
coefficient	O
and	O
exponent	O
parts	O
and	O
independently	O
huffman	B-General_Concept
coded	I-General_Concept
.	O
</s>
<s>
At	O
low	O
bit	O
rates	O
,	O
line	B-Algorithm
spectral	I-Algorithm
pairs	I-Algorithm
(	O
typically	O
less	O
than	O
17kbit/s	O
)	O
and	O
a	O
form	O
of	O
noise	O
coding	O
(	O
typically	O
less	O
than	O
33kbit/s	O
)	O
can	O
also	O
be	O
used	O
to	O
improve	O
quality	O
.	O
</s>
<s>
Like	O
AAC	B-Application
and	O
Ogg	B-Algorithm
Vorbis	I-Algorithm
,	O
WMA	B-Application
was	O
intended	O
to	O
address	O
perceived	O
deficiencies	O
in	O
the	O
MP3	B-Application
standard	O
.	O
</s>
<s>
All	O
three	O
are	O
pure	O
transform	O
codecs	B-General_Concept
.	O
</s>
<s>
Furthermore	O
,	O
the	O
MDCT	O
implementation	O
used	O
in	O
WMA	B-Application
is	O
essentially	O
a	O
superset	O
of	O
those	O
used	O
in	O
Ogg	O
and	O
AAC	B-Application
such	O
that	O
WMA	B-Application
iMDCT	O
and	O
windowing	O
routines	O
can	O
be	O
used	O
to	O
decode	O
AAC	B-Application
and	O
Ogg	B-Algorithm
Vorbis	I-Algorithm
almost	O
unmodified	O
.	O
</s>
<s>
However	O
,	O
quantization	O
and	O
stereo	O
coding	O
is	O
handled	O
differently	O
in	O
each	O
codec	B-General_Concept
.	O
</s>
<s>
The	O
primary	O
distinguishing	O
trait	O
of	O
the	O
WMA	B-Application
Standard	O
format	O
is	O
its	O
unique	O
use	O
of	O
5	O
different	O
block	O
sizes	O
,	O
compared	O
to	O
MP3	B-Application
,	O
AAC	B-Application
,	O
and	O
Ogg	B-Algorithm
Vorbis	I-Algorithm
which	O
each	O
restrict	O
files	O
to	O
just	O
two	O
sizes	O
.	O
</s>
<s>
WMA	B-Application
Pro	O
extends	O
this	O
by	O
adding	O
a	O
6th	O
block	O
size	O
used	O
at	O
88.2/96kHz	O
sampling	O
rate	O
.	O
</s>
<s>
Certified	O
PlaysForSure	O
devices	O
,	O
as	O
well	O
as	O
a	O
large	O
number	O
of	O
uncertified	O
devices	O
,	O
ranging	O
from	O
portable	O
hand-held	O
music	O
players	O
to	O
set-top	O
DVD	B-Device
players	I-Device
,	O
support	O
the	O
playback	O
of	O
WMA	B-Application
files	I-Application
.	O
</s>
<s>
Most	O
PlaysForSure-certified	O
online	O
stores	O
distribute	O
content	O
using	O
this	O
codec	B-General_Concept
only	O
.	O
</s>
<s>
In	O
2005	O
,	O
Nokia	O
announced	O
its	O
plans	O
to	O
support	O
WMA	B-Application
playback	O
in	O
future	O
Nokia	O
handsets	O
.	O
</s>
<s>
In	O
the	O
same	O
year	O
,	O
an	O
update	O
was	O
made	O
available	O
for	O
the	O
PlayStation	B-Operating_System
Portable	I-Operating_System
(	O
version	O
2.60	O
)	O
which	O
allowed	O
WMA	B-Application
files	I-Application
to	O
be	O
played	O
on	O
the	O
device	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
Professional	O
(	O
WMA	B-Application
Pro	O
)	O
is	O
an	O
improved	O
lossy	B-Algorithm
codec	B-General_Concept
closely	O
related	O
to	O
WMA	B-Application
standards	O
.	O
</s>
<s>
Notably	O
,	O
many	O
of	O
the	O
WMA	B-Application
standard	O
's	O
low	O
bitrate	O
features	O
have	O
been	O
removed	O
,	O
as	O
the	O
core	O
codec	B-General_Concept
is	O
designed	O
for	O
efficient	O
coding	O
at	O
most	O
bitrates	O
.	O
</s>
<s>
Its	O
main	O
competitors	O
include	O
AAC	B-Application
,	O
HE-AAC	O
,	O
Vorbis	B-Algorithm
,	O
Dolby	O
Digital	O
,	O
and	O
DTS	O
.	O
</s>
<s>
WMA	B-Application
Pro	O
also	O
supports	O
dynamic	O
range	O
compression	O
,	O
which	O
reduces	O
the	O
volume	O
difference	O
between	O
the	O
loudest	O
and	O
quietest	O
sounds	O
in	O
the	O
audio	O
track	O
.	O
</s>
<s>
According	O
to	O
Microsoft	O
's	O
Amir	O
Majidimehr	O
,	O
WMA	B-Application
Pro	O
could	O
theoretically	O
go	O
beyond	O
7.1	O
surround	O
sound	O
and	O
support	O
"	O
an	O
unlimited	O
number	O
of	O
channels	O
"	O
;	O
however	O
,	O
Microsoft	O
chose	O
to	O
limit	O
its	O
current	O
capability	O
to	O
eight	O
(	O
7.1	O
discrete	O
channels	O
)	O
.	O
</s>
<s>
The	O
codec	B-General_Concept
's	O
bit	O
stream	O
syntax	O
was	O
frozen	O
at	O
the	O
first	O
version	O
,	O
WMA	B-Application
9	O
Pro	O
.	O
</s>
<s>
Later	O
versions	O
of	O
WMA	B-Application
Pro	O
introduced	O
low-bit	O
rate	O
encoding	O
,	O
low-delay	O
audio	O
,	O
frequency	O
interpolation	O
mode	O
,	O
and	O
an	O
expanded	O
range	O
of	O
sampling	O
rate	O
and	O
bit-depth	O
encoding	O
options	O
.	O
</s>
<s>
A	O
WMA	B-Application
10	O
Pro	O
file	O
compressed	O
with	O
frequency	O
interpolation	O
mode	O
comprises	O
a	O
WMA	B-Application
9	O
Pro	O
track	O
encoded	O
at	O
half	O
the	O
original	O
sampling	O
rate	O
,	O
which	O
is	O
then	O
restored	O
using	O
a	O
new	O
compression	B-General_Concept
algorithm	I-General_Concept
.	O
</s>
<s>
In	O
this	O
situation	O
,	O
WMA	B-Application
9	O
Pro	O
players	O
which	O
have	O
not	O
been	O
updated	O
to	O
the	O
WMA	B-Application
10	O
Pro	O
codec	B-General_Concept
can	O
only	O
decode	O
the	O
lower	O
quality	O
WMA	B-Application
9	O
Pro	O
stream	O
.	O
</s>
<s>
Starting	O
with	O
WMA	B-Application
10	O
Pro	O
,	O
eight	O
channel	O
encoding	O
starts	O
at	O
128kbit/s	O
,	O
and	O
tracks	O
can	O
be	O
encoded	O
at	O
the	O
native	O
audio	O
CD	O
resolution	O
(	O
44.1kHz	O
,	O
16-bit	O
)	O
,	O
previously	O
the	O
domain	O
of	O
WMA	B-Application
Standard	O
.	O
</s>
<s>
Despite	O
a	O
growing	O
number	O
of	O
supported	O
devices	O
and	O
its	O
superiority	O
over	O
WMA	B-Application
,	O
WMA	B-Application
Pro	O
still	O
has	O
little	O
hardware	O
and	O
software	O
support	O
.	O
</s>
<s>
Some	O
notable	O
exceptions	O
to	O
this	O
are	O
the	O
Microsoft	B-Device
Zune	I-Device
(	O
limited	O
to	O
stereo	O
)	O
,	O
Xbox	B-Operating_System
360	I-Operating_System
,	O
Windows	O
Mobile-powered	O
devices	O
with	O
Windows	B-Device
Media	I-Device
Player	I-Device
10	I-Device
Mobile	O
,	O
newer	O
Toshiba	O
Gigabeat	O
and	O
Motorola	O
devices	O
,	O
and	O
devices	O
running	O
recent	O
versions	O
of	O
the	O
Rockbox	B-Application
alternative	O
firmware	O
.	O
</s>
<s>
In	O
addition	O
,	O
WMA	B-Application
Pro	O
is	O
a	O
requirement	O
for	O
the	O
WMV	B-Device
HD	O
certification	O
program	O
.	O
</s>
<s>
On	O
the	O
software	O
side	O
,	O
Verizon	B-Application
utilizes	O
WMA	B-Application
10	O
Pro	O
for	O
its	O
V	O
CAST	O
Music	O
Service	O
,	O
and	O
Windows	B-Device
Media	I-Device
Player	I-Device
11	I-Device
has	O
promoted	O
the	O
codec	B-General_Concept
as	O
an	O
alternative	O
to	O
WMA	B-Application
for	O
copying	O
audio	O
CD	O
tracks	O
.	O
</s>
<s>
WMA	B-Application
Pro	O
is	O
supported	O
in	O
Silverlight	O
as	O
of	O
version	O
2	O
(	O
though	O
only	O
in	O
stereo	O
mode	O
)	O
.	O
</s>
<s>
In	O
the	O
absence	O
of	O
the	O
appropriate	O
audio	O
hardware	O
,	O
WMA	B-Application
Pro	O
can	O
automatically	O
downmix	O
multichannel	O
audio	O
to	O
stereo	O
or	O
mono	O
,	O
and	O
24-bit	O
resolution	O
to	O
16-bit	O
during	O
playback	O
.	O
</s>
<s>
A	O
notable	O
example	O
of	O
WMA	B-Application
Pro	O
being	O
used	O
instead	O
of	O
WMA	B-Application
Standard	O
is	O
the	O
NBC	O
Olympics	O
website	O
which	O
uses	O
WMA	B-Application
10	O
Pro	O
in	O
its	O
low-bitrate	O
mode	O
at	O
48	O
kbit/s	O
.	O
</s>
<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
9	O
Lossless	B-Algorithm
is	O
a	O
lossless	B-Algorithm
incarnation	O
of	O
Windows	B-Application
Media	I-Application
Audio	I-Application
,	O
an	O
audio	B-Algorithm
codec	I-Algorithm
by	O
Microsoft	O
,	O
released	O
in	O
early	O
2003	O
.	O
</s>
<s>
WMA	B-Application
Lossless	B-Algorithm
uses	O
the	O
same	O
.WMA	B-Application
file	O
extension	O
as	O
other	O
Windows	B-Application
Media	I-Application
Audio	I-Application
formats	O
.	O
</s>
<s>
It	O
supports	O
6	O
discrete	O
channels	O
and	O
up	O
to	O
24-bit/96kHz	O
lossless	B-Algorithm
audio	O
.	O
</s>
<s>
The	O
format	O
has	O
never	O
been	O
publicly	O
documented	O
,	O
although	O
an	O
open-source	B-Application
decoder	O
has	O
been	O
reverse-engineered	O
for	O
non-Microsoft	O
platforms	O
by	O
the	O
libav	B-Language
and	O
ffmpeg	B-Library
projects	O
.	O
</s>
<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
Lossless	B-Algorithm
(	O
WMA	B-Application
Lossless	B-Algorithm
)	O
is	O
a	O
lossless	B-Algorithm
audio	B-Algorithm
codec	I-Algorithm
that	O
competes	O
with	O
ATRAC	O
Advanced	O
Lossless	B-Algorithm
,	O
Dolby	O
TrueHD	O
,	O
DTS-HD	O
Master	O
Audio	O
,	O
Shorten	B-Operating_System
,	O
Monkey	B-Language
's	I-Language
Audio	I-Language
,	O
FLAC	B-Application
,	O
Apple	B-Algorithm
Lossless	I-Algorithm
,	O
and	O
WavPack	B-Application
(	O
Since	O
late	O
2011	O
,	O
the	O
last	O
three	O
have	O
the	O
advantage	O
of	O
being	O
open	B-Application
source	I-Application
software	I-Application
and	O
available	O
for	O
nearly	O
any	O
operating	B-General_Concept
system	I-General_Concept
.	O
)	O
</s>
<s>
The	O
first	O
version	O
of	O
the	O
codec	B-General_Concept
,	O
WMA	B-Application
9	O
Lossless	B-Algorithm
,	O
and	O
its	O
revisions	O
support	O
up	O
to	O
96kHz	O
,	O
24-bit	O
audio	O
for	O
up	O
to	O
6	O
discrete	O
channels	O
(	O
5.1	O
channel	O
surround	O
)	O
with	O
dynamic	O
range	O
compression	O
control	O
.	O
</s>
<s>
Hardware	O
support	O
for	O
the	O
codec	B-General_Concept
is	O
available	O
on	O
the	O
Cowon	O
A3	O
,	O
Cowon	O
S9	O
,	O
Bang	O
&	O
Olufsen	O
Serenata	O
Sony	O
Walkman	O
NWZ-A	O
and	O
NWZ-S	O
series	O
,	O
Zune	B-Device
4	O
,	O
8	O
,	O
80	O
30	O
,	O
Zune	B-Device
120	O
(	O
with	O
firmware	O
version	O
2.2	O
or	O
later	O
)	O
and	O
the	O
Zune	B-Device
HD	O
,	O
Xbox	B-Operating_System
360	I-Operating_System
,	O
Windows	O
Mobile-powered	O
devices	O
with	O
Windows	B-Device
Media	I-Device
Player	I-Device
10	I-Device
Mobile	O
,	O
Windows	O
Phone	O
(	O
version	O
8	O
and	O
above	O
)	O
,	O
Toshiba	O
Gigabeat	O
S	O
and	O
V	O
models	O
,	O
Toshiba	O
T-400	O
,	O
the	O
Meizu	O
M3	O
,	O
and	O
Best	O
Buy	O
's	O
Insignia	O
NS-DV	O
,	O
Pilot	O
,	O
and	O
Sport	O
music	O
players	O
.	O
</s>
<s>
Like	O
WMA	B-Application
Standard	O
,	O
WMA	B-Application
Lossless	B-Algorithm
is	O
being	O
used	O
by	O
a	O
few	O
online	O
stores	O
to	O
distribute	O
music	O
online	O
.	O
</s>
<s>
Similar	O
to	O
WMA	B-Application
Pro	O
,	O
the	O
WMA	B-Application
Lossless	B-Algorithm
decoder	O
can	O
perform	O
downmixing	O
when	O
capable	O
audio	O
hardware	O
is	O
not	O
present	O
.	O
</s>
<s>
As	O
of	O
2012	O
,	O
the	O
ffmpeg	B-Library
and	O
libav	B-Language
projects	O
have	O
open	B-Application
source	I-Application
WMA	B-Application
Lossless	B-Algorithm
decoders	O
based	O
on	O
reverse	O
engineering	O
of	O
the	O
official	O
decoder	O
.	O
</s>
<s>
Only	O
16-bit	O
WMA	B-Application
files	I-Application
can	O
be	O
successfully	O
decoded	O
by	O
ffmpeg	B-Library
as	O
of	O
June	O
20	O
,	O
2012	O
.	O
</s>
<s>
Windows	B-Application
Media	I-Application
Audio	I-Application
Voice	O
(	O
WMA	B-Application
Voice	O
)	O
is	O
a	O
lossy	B-Algorithm
audio	B-Algorithm
codec	I-Algorithm
that	O
competes	O
with	O
Speex	B-Application
(	O
used	O
in	O
Microsoft	O
's	O
own	O
Xbox	B-Application
Live	I-Application
online	O
service	O
)	O
,	O
ACELP	B-Algorithm
,	O
and	O
other	O
codecs	B-General_Concept
.	O
</s>
<s>
Designed	O
for	O
low-bandwidth	O
,	O
voice	O
playback	O
applications	O
,	O
it	O
employs	O
low-pass	O
and	O
high-pass	O
filtering	O
of	O
sound	O
outside	O
the	O
human	O
speech	O
frequency	O
range	O
to	O
achieve	O
higher	O
compression	O
efficiency	O
than	O
WMA	B-Application
.	O
</s>
<s>
It	O
can	O
automatically	O
detect	O
sections	O
of	O
an	O
audio	O
track	O
containing	O
both	O
voice	O
and	O
music	O
and	O
use	O
the	O
standard	O
WMA	B-Application
compression	B-General_Concept
algorithm	I-General_Concept
instead	O
.	O
</s>
<s>
WMA	B-Application
Voice	O
supports	O
up	O
to	O
22.05kHz	O
for	O
a	O
single	O
channel	O
(	O
mono	O
)	O
only	O
.	O
</s>
<s>
Encoding	O
is	O
limited	O
to	O
constant	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
(	O
CBR	O
)	O
and	O
up	O
to	O
20kbit/s	O
.	O
</s>
<s>
The	O
first	O
and	O
only	O
version	O
of	O
the	O
codec	B-General_Concept
is	O
WMA	B-Application
9	O
Voice	O
.	O
</s>
<s>
Windows	O
Mobile-powered	O
devices	O
with	O
Windows	B-Device
Media	I-Device
Player	I-Device
10	I-Device
Mobile	O
have	O
native	O
support	O
for	O
WMA	B-Application
9	O
Voice	O
playback	O
.	O
</s>
<s>
In	O
addition	O
,	O
BBC	O
World	O
Service	O
has	O
employed	O
WMA	B-Application
Voice	O
for	O
its	O
Internet	O
radio	O
streaming	O
service	O
.	O
</s>
<s>
See	O
codec	B-General_Concept
listening	O
test	O
for	O
a	O
table	O
of	O
double-blind	O
listening	O
test	O
results	O
.	O
</s>
<s>
Microsoft	O
claims	O
that	O
audio	O
encoded	O
with	O
WMA	B-Application
sounds	O
better	O
than	O
MP3	B-Application
at	O
the	O
same	O
bit	O
rate	O
;	O
Microsoft	O
also	O
claims	O
that	O
audio	O
encoded	O
with	O
WMA	B-Application
at	O
lower	O
bit	O
rates	O
sound	O
better	O
than	O
MP3	B-Application
at	O
higher	O
bit	O
rates	O
.	O
</s>
<s>
Double	O
blind	O
listening	O
tests	O
with	O
other	O
lossy	B-Algorithm
audio	B-Algorithm
codecs	I-Algorithm
have	O
shown	O
varying	O
results	O
,	O
from	O
failure	O
to	O
support	O
Microsoft	O
's	O
claims	O
about	O
its	O
superior	O
quality	O
to	O
supremacy	O
over	O
other	O
codecs	B-General_Concept
.	O
</s>
<s>
One	O
independent	O
test	O
conducted	O
in	O
May	O
2004	O
at	O
128kbit/s	O
showed	O
that	O
WMA	B-Application
was	O
roughly	O
equivalent	O
to	O
LAME	B-Algorithm
MP3	B-Application
;	O
inferior	O
to	O
AAC	B-Application
and	O
Vorbis	B-Algorithm
;	O
and	O
superior	O
to	O
ATRAC3	O
(	O
software	O
version	O
)	O
.	O
</s>
<s>
At	O
,	O
WMA	B-Application
Standard	O
was	O
noticeably	O
better	O
than	O
LAME	B-Algorithm
MP3	B-Application
,	O
but	O
not	O
better	O
than	O
other	O
modern	O
codecs	B-General_Concept
in	O
a	O
collective	O
,	O
independent	O
test	O
in	O
July	O
2004	O
.	O
</s>
<s>
At	O
,	O
WMA	B-Application
10	O
Pro	O
was	O
ranked	O
second	O
after	O
Nero	O
HE-AAC	O
and	O
better	O
than	O
WMA	B-Application
9.2	O
in	O
an	O
independent	O
listening	O
test	O
organized	O
and	O
supported	O
by	O
Sebastian	O
Mares	O
and	O
Hydrogenaudio	O
Forums	O
in	O
December	O
2006	O
.	O
</s>
<s>
This	O
test	O
,	O
however	O
,	O
used	O
CBR	O
for	O
WMA	B-Application
10	O
Pro	O
and	O
VBR	O
for	O
the	O
other	O
codecs	B-General_Concept
.	O
</s>
<s>
At	O
,	O
WMA	B-Application
Pro	O
outperformed	O
Nero	O
HE-AAC	O
in	O
a	O
listening	O
test	O
commissioned	O
by	O
Microsoft	O
but	O
independently	O
performed	O
by	O
the	O
National	O
Software	O
Testing	O
Labs	O
in	O
1999	O
.	O
</s>
<s>
Out	O
of	O
300	O
participants	O
,	O
"	O
71%	O
of	O
all	O
listeners	O
indicated	O
that	O
WMA	B-Application
Pro	O
was	O
equal	O
to	O
or	O
better	O
than	O
HE	O
AAC.	O
"	O
</s>
<s>
However	O
,	O
a	O
September	O
2003	O
public	O
listening	O
test	O
conducted	O
by	O
Roberto	O
Amorim	O
found	O
that	O
listeners	O
preferred	O
128kbit/s	O
MP3	B-Application
to	O
64kbit/s	O
WMA	B-Application
audio	O
with	O
greater	O
than	O
99%	O
confidence	O
.	O
</s>
<s>
At	O
and	O
,	O
WMA	B-Application
had	O
lower	O
quality	O
than	O
HE-AAC	O
,	O
AAC-LC	B-Application
,	O
and	O
Vorbis	B-Algorithm
;	O
near-equivalent	O
quality	O
to	O
MP3	B-Application
,	O
and	O
better	O
quality	O
than	O
MPC	B-Algorithm
in	O
individual	O
tests	O
done	O
in	O
2005	O
.	O
</s>
<s>
At	O
,	O
there	O
was	O
a	O
four-way	O
tie	O
between	O
aoTuV	B-Algorithm
Vorbis	B-Algorithm
,	O
LAME	B-Algorithm
MP3	B-Application
,	O
WMA	B-Application
9	O
Pro	O
and	O
AAC	B-Application
in	O
a	O
large	O
scale	O
test	O
in	O
January	O
2006	O
,	O
with	O
each	O
codec	B-General_Concept
sounding	O
close	O
to	O
the	O
uncompressed	B-General_Concept
music	O
file	O
for	O
most	O
listeners	O
.	O
</s>
<s>
At	O
,	O
WMA	B-Application
9	O
Pro	O
delivered	O
full-spectrum	O
response	O
at	O
half	O
the	O
bit	O
rate	O
required	O
for	O
DTS	O
in	O
a	O
comparative	O
test	O
done	O
by	O
EDN	O
in	O
October	O
2003	O
.	O
</s>
<s>
Microsoft	O
's	O
claims	O
of	O
WMA	B-Application
sound	O
quality	O
have	O
frequently	O
drawn	O
complaints	O
.	O
</s>
<s>
"	O
Some	O
audiophiles	O
challenge	O
Microsoft	O
's	O
claims	O
regarding	O
WMA	B-Application
's	O
quality	O
"	O
,	O
according	O
to	O
a	O
published	O
article	O
from	O
EDN	O
.	O
</s>
<s>
Another	O
article	O
from	O
MP3	B-Application
Developments	O
wrote	O
that	O
Microsoft	O
's	O
claim	O
about	O
CD-quality	O
audio	O
at	O
64kbit/s	O
with	O
WMA	B-Application
was	O
"	O
very	O
far	O
from	O
the	O
truth	O
"	O
.	O
</s>
<s>
At	O
the	O
early	O
stages	O
of	O
WMA	B-Application
's	O
development	O
,	O
a	O
representative	O
from	O
RealNetworks	O
claimed	O
that	O
WMA	B-Application
was	O
a	O
"	O
clear	O
and	O
futile	O
effort	O
by	O
Microsoft	O
to	O
catch	O
up	O
with	O
RealAudio	B-Algorithm
8	O
"	O
.	O
</s>
<s>
Microsoft	O
has	O
sometimes	O
claimed	O
that	O
the	O
sound	O
quality	O
of	O
WMA	B-Application
at	O
64kbit/s	O
equals	O
or	O
exceeds	O
that	O
of	O
MP3	B-Application
at	O
128kbit/s	O
(	O
both	O
WMA	B-Application
and	O
MP3	B-Application
are	O
considered	O
near-transparent	O
at	O
192kbit/s	O
by	O
most	O
listeners	O
)	O
.	O
</s>
<s>
In	O
a	O
1999	O
study	O
funded	O
by	O
Microsoft	O
,	O
National	O
Software	O
Testing	O
Laboratories	O
(	O
NSTL	O
)	O
found	O
that	O
listeners	O
preferred	O
WMA	B-Application
at	O
64kbit/s	O
to	O
MP3	B-Application
at	O
128kbit/s	O
(	O
as	O
encoded	O
by	O
MusicMatch	B-Application
Jukebox	I-Application
)	O
.	O
</s>
<s>
Both	O
MP3	B-Application
and	O
WMA	B-Application
encoders	O
have	O
undergone	O
active	O
development	O
and	O
improvement	O
for	O
many	O
years	O
,	O
so	O
their	O
relative	O
quality	O
may	O
change	O
over	O
time	O
.	O
</s>
<s>
Apart	O
from	O
Windows	B-Device
Media	I-Device
Player	I-Device
,	O
most	O
of	O
the	O
WMA	B-Application
compression	O
formats	O
can	O
be	O
played	O
using	O
ALLPlayer	B-Language
,	O
VLC	B-Application
media	I-Application
player	I-Application
,	O
Media	B-Language
Player	I-Language
Classic	I-Language
,	O
MPlayer	B-Application
,	O
RealPlayer	B-Application
,	O
Winamp	B-Application
,	O
Zune	B-Protocol
Software	I-Protocol
(	O
with	O
certain	O
limitationsDSP	O
plugin	O
support	O
and	O
DirectSound	O
output	O
is	O
disabled	O
using	O
the	O
default	O
WMA	B-Application
plugin	O
)	O
,	O
and	O
many	O
other	O
software	O
media	B-Device
players	I-Device
.	O
</s>
<s>
The	O
Microsoft	B-Device
Zune	I-Device
media	O
management	O
software	O
supports	O
most	O
WMA	B-Application
codecs	B-General_Concept
,	O
but	O
uses	O
a	O
variation	O
of	O
Windows	B-Device
Media	I-Device
DRM	O
which	O
is	O
used	O
by	O
PlaysForSure	O
.	O
</s>
<s>
The	O
FFmpeg	B-Library
project	O
has	O
reverse-engineered	O
and	O
re-implemented	O
the	O
WMA	B-Application
codecs	B-General_Concept
to	O
allow	O
their	O
use	O
on	O
POSIX-compliant	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
Linux	B-Application
.	O
</s>
<s>
The	O
Rockbox	B-Application
project	O
further	O
extended	O
this	O
codec	B-General_Concept
to	O
be	O
suitable	O
for	O
embedded	O
cores	O
,	O
allowing	O
playback	O
on	O
portable	O
MP3	B-Application
players	O
and	O
cell	O
phones	O
running	O
open	B-Application
source	I-Application
software	I-Application
.	O
</s>
<s>
RealNetworks	O
has	O
announced	O
plans	O
to	O
support	O
playback	O
of	O
DRM-free	O
WMA	B-Application
files	I-Application
in	O
RealPlayer	B-Application
for	O
Linux	B-Application
.	O
</s>
<s>
On	O
the	O
Macintosh	B-Device
platform	O
,	O
Microsoft	O
released	O
a	O
PowerPC	B-Architecture
version	O
of	O
Windows	B-Device
Media	I-Device
Player	I-Device
for	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
in	O
2003	O
,	O
but	O
further	O
development	O
of	O
the	O
software	O
has	O
ceased	O
.	O
</s>
<s>
Microsoft	O
currently	O
endorses	O
the	O
third-party	O
Flip4Mac	B-Operating_System
WMA	B-Application
,	O
a	O
QuickTime	B-Application
component	O
that	O
allows	O
Macintosh	B-Device
users	O
to	O
play	O
WMA	B-Application
files	I-Application
in	O
any	O
player	O
that	O
uses	O
the	O
QuickTime	B-Application
framework	O
.	O
</s>
<s>
Flip4Mac	B-Operating_System
,	O
however	O
,	O
does	O
not	O
currently	O
support	O
the	O
Windows	B-Application
Media	I-Application
Audio	I-Application
Voice	O
codec	B-General_Concept
.	O
</s>
<s>
The	O
core	O
Android	B-Application
platform	I-Application
does	O
not	O
itself	O
support	O
WMA	B-Application
,	O
but	O
there	O
is	O
third-party	O
WMA	B-Application
software	O
for	O
Android	B-Application
devices	O
.	O
</s>
<s>
WMA	B-Application
format	O
can	O
be	O
played	O
on	O
almost	O
all	O
Windows	B-Operating_System
Mobile	I-Operating_System
and	O
later	O
Windows	O
Phone	O
devices	O
.	O
</s>
<s>
There	O
are	O
many	O
proprietary	B-Application
and	O
Open	B-Application
source	I-Application
software	I-Application
packages	O
that	O
can	O
export	O
audio	O
in	O
WMA	B-Application
format	O
,	O
including	O
amongst	O
many	O
others	O
Windows	B-Device
Media	I-Device
Player	I-Device
,	O
Windows	B-Application
Movie	I-Application
Maker	I-Application
,	O
Microsoft	B-Application
Expression	I-Application
Encoder	I-Application
,	O
Sony	B-Application
Sound	I-Application
Forge	I-Application
,	O
GOM	B-Application
Player	I-Application
,	O
RealPlayer	B-Application
,	O
Adobe	B-Operating_System
Premiere	I-Operating_System
Pro	I-Operating_System
,	O
Adobe	B-Operating_System
Audition	I-Operating_System
,	O
Adobe	B-Operating_System
Soundbooth	I-Operating_System
,	O
and	O
VLC	B-Application
media	I-Application
player	I-Application
.	O
</s>
<s>
Microsoft	B-Application
Office	I-Application
OneNote	I-Application
supports	O
encoding	O
in	O
all	O
WMA	B-Application
codecs	B-General_Concept
,	O
and	O
Windows	B-Protocol
Media	I-Protocol
Encoder	I-Protocol
supports	O
all	O
available	O
bit	O
rate	O
and	O
resolution	O
options	O
as	O
well	O
.	O
</s>
<s>
The	O
WMA	B-Application
codecs	B-General_Concept
are	O
most	O
often	O
used	O
with	O
the	O
ASF	O
container	O
format	O
,	O
which	O
has	O
an	O
optional	O
DRM	O
facility	O
.	O
</s>
<s>
Windows	B-Device
Media	I-Device
DRM	O
,	O
which	O
can	O
be	O
used	O
in	O
conjunction	O
with	O
WMA	B-Application
,	O
supports	O
time-limited	O
music	O
subscription	O
services	O
such	O
as	O
those	O
offered	O
by	O
unlimited	O
download	O
services	O
,	O
including	O
MTV	O
's	O
URGE	O
,	O
Napster	B-Application
,	O
Rhapsody	O
,	O
Yahoo	O
!	O
</s>
<s>
Windows	B-Device
Media	I-Device
DRM	O
,	O
a	O
component	O
of	O
PlaysForSure	O
and	O
Windows	B-Application
Media	I-Application
Connect	I-Application
,	O
is	O
supported	O
on	O
many	O
modern	O
portable	O
audio	O
devices	O
and	O
streaming	O
media	O
clients	O
such	O
as	O
Roku	O
,	O
SoundBridge	O
,	O
Xbox	B-Operating_System
360	I-Operating_System
,	O
and	O
Wii	B-Operating_System
.	O
</s>
<s>
Players	O
that	O
support	O
the	O
WMA	B-Application
format	O
but	O
not	O
Windows	B-Device
Media	I-Device
DRM	O
cannot	O
play	O
DRM-protected	O
files	O
.	O
</s>
