<s>
x264	B-Language
is	O
a	O
free	B-License
and	I-License
open-source	I-License
software	I-License
library	O
and	O
a	O
command-line	B-Application
utility	O
developed	O
by	O
VideoLAN	B-Application
for	O
encoding	O
video	O
streams	O
into	O
the	O
H.264/MPEG	B-Application
-4	I-Application
AVC	I-Application
video	B-Algorithm
coding	I-Algorithm
format	I-Algorithm
.	O
</s>
<s>
It	O
is	O
released	O
under	O
the	O
terms	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
x264	B-Language
was	O
originally	O
developed	O
by	O
Laurent	O
Aimar	O
,	O
who	O
stopped	O
development	O
in	O
2004	O
after	O
being	O
hired	O
by	O
ATEME	O
.	O
</s>
<s>
Today	O
,	O
x264	B-Language
is	O
primarily	O
developed	O
by	O
Anton	O
Mitrofanov	O
and	O
Henrik	O
Gramner	O
.	O
</s>
<s>
x264	B-Language
provides	O
a	O
command	B-Application
line	I-Application
interface	I-Application
as	O
well	O
as	O
an	O
API	B-Application
.	O
</s>
<s>
The	O
former	O
is	O
used	O
by	O
many	O
graphical	B-Application
user	I-Application
interfaces	I-Application
,	O
such	O
as	O
Staxrip	O
and	O
MeGUI	O
.	O
</s>
<s>
The	O
latter	O
is	O
used	O
by	O
many	O
other	O
interfaces	O
,	O
such	O
as	O
HandBrake	B-Language
and	O
FFmpeg	B-Library
.	O
</s>
<s>
x264	B-Language
implements	O
a	O
large	O
number	O
of	O
features	O
compared	O
to	O
other	O
H.264	B-Application
encoders	O
.	O
</s>
<s>
x264	B-Language
contains	O
some	O
psychovisual	O
enhancements	O
which	O
aim	O
to	O
increase	O
the	O
subjective	B-Device
video	I-Device
quality	I-Device
of	O
the	O
encoded	O
video	O
.	O
</s>
<s>
Adaptive	O
quantisation	O
in	O
two	O
modes	O
using	O
VAQ	B-Algorithm
.	O
</s>
<s>
Psychovisual	O
rate	B-General_Concept
–	I-General_Concept
distortion	I-General_Concept
optimization	I-General_Concept
which	O
attempts	O
to	O
maintain	O
a	O
similar	O
complexity	O
.	O
</s>
<s>
The	O
complexity	O
is	O
measured	O
using	O
a	O
combination	O
of	O
sum-of-squares	O
optimization	O
(	O
SSD	O
)	O
and	O
sum	B-Algorithm
of	I-Algorithm
absolute	I-Algorithm
transformed	I-Algorithm
differences	I-Algorithm
(	O
SATD	B-Algorithm
)	O
.	O
</s>
<s>
x264	B-Language
has	O
won	O
awards	O
in	O
the	O
following	O
codec	O
comparisons	O
:	O
</s>
<s>
x264	B-Language
has	O
SIMD	B-Device
assembly	B-Language
code	I-Language
acceleration	O
on	O
x86	B-Operating_System
,	O
PowerPC	B-Architecture
(	O
using	O
AltiVec	B-General_Concept
)	O
,	O
and	O
ARMv7	B-Architecture
(	O
using	O
NEON	O
)	O
platforms	O
.	O
</s>
<s>
x264	B-Language
is	O
able	O
to	O
use	O
Periodic	O
Intra	O
Refresh	O
instead	O
of	O
keyframes	O
,	O
which	O
enables	O
each	O
frame	O
to	O
be	O
capped	O
to	O
the	O
same	O
size	O
enabling	O
each	O
slice	O
to	O
be	O
immediately	O
transmitted	O
in	O
a	O
single	O
UDP	O
or	O
TCP	O
packet	O
and	O
on	O
arrival	O
immediately	O
decoded	O
.	O
</s>
<s>
In	O
April	O
2010	O
,	O
the	O
x264	B-Language
project	O
announced	O
full	O
Blu-ray	O
compliant	O
video	O
encoding	O
capability	O
making	O
x264	B-Language
the	O
first	O
free	O
Blu-ray	O
compliant	O
software	O
H.264	B-Application
encoder	O
.	O
</s>
<s>
x264	B-Language
has	O
always	O
had	O
the	O
ability	O
to	O
create	O
video	O
streams	O
that	O
are	O
playable	O
on	O
most	O
Blu-ray	O
devices	O
.	O
</s>
<s>
The	O
default	O
x264	B-Language
preset	O
chooses	O
adequate	O
compatibility	O
for	O
Blu-ray	O
players	O
but	O
it	O
is	O
now	O
possible	O
to	O
choose	O
more	O
complex	O
conversion	O
settings	O
while	O
simply	O
maintaining	O
compatibility	O
by	O
explicitly	O
enabling	O
Blu-ray	O
compatibility	O
mode	O
.	O
</s>
<s>
Blu-ray	O
compatibility	O
can	O
be	O
useful	O
when	O
striving	O
for	O
cross	O
device	O
compatibility	O
,	O
especially	O
in	O
the	O
realm	O
of	O
high	B-Application
definition	I-Application
hardware	I-Application
media	I-Application
players	I-Application
.	O
</s>
<s>
x264	B-Language
has	O
been	O
used	O
to	O
author	O
commercial	O
Blu-ray	O
Disc	O
titles	O
released	O
by	O
Warner	O
Bros	O
.	O
</s>
<s>
In	O
November	O
2010	O
,	O
Fiona	O
Glaser	O
,	O
an	O
x264	B-Language
developer	O
,	O
published	O
information	O
in	O
which	O
she	O
claims	O
that	O
one	O
of	O
Tandberg	O
Telecom	O
's	O
(	O
a	O
Cisco	O
Systems	O
subsidiary	O
)	O
patent	O
applications	O
from	O
December	O
2008	O
contains	O
a	O
step-by-step	O
description	O
of	O
an	O
algorithm	O
she	O
committed	O
to	O
the	O
x264	B-Language
codebase	O
around	O
two	O
months	O
earlier	O
.	O
</s>
<s>
This	O
was	O
relayed	O
by	O
media	O
,	O
which	O
remarked	O
that	O
the	O
company	O
who	O
filed	O
the	O
patent	O
was	O
following	O
the	O
x264	B-Language
project	O
IRC	O
development	O
channel	O
and	O
was	O
known	O
to	O
the	O
project	O
developers	O
,	O
leading	O
to	O
Tandberg	O
claiming	O
that	O
they	O
discovered	O
the	O
algorithm	O
independently	O
.	O
</s>
