<s>
Xvid	B-Algorithm
(	O
formerly	O
"	O
XviD	B-Algorithm
"	O
)	O
is	O
a	O
video	B-Application
codec	I-Application
library	B-Library
following	O
the	O
MPEG-4	B-Algorithm
video	B-Algorithm
coding	I-Algorithm
standard	I-Algorithm
,	O
specifically	O
MPEG-4	B-Application
Part	I-Application
2	I-Application
Advanced	I-Application
Simple	I-Application
Profile	I-Application
(	O
ASP	O
)	O
.	O
</s>
<s>
It	O
uses	O
ASP	O
features	O
such	O
as	O
b-frames	O
,	O
global	O
and	O
quarter	O
pixel	O
motion	B-Algorithm
compensation	I-Algorithm
,	O
lumi	B-Application
masking	I-Application
,	O
trellis	B-General_Concept
quantization	I-General_Concept
,	O
and	O
H.263	B-Algorithm
,	O
MPEG	O
and	O
custom	O
quantization	B-Algorithm
matrices	I-Algorithm
.	O
</s>
<s>
Xvid	B-Algorithm
is	O
a	O
primary	O
competitor	O
of	O
the	O
DivX	B-Application
Pro	I-Application
Codec	B-Application
.	O
</s>
<s>
In	O
contrast	O
with	O
the	O
DivX	B-Application
codec	I-Application
,	O
which	O
is	O
proprietary	B-Application
software	I-Application
developed	O
by	O
DivX	B-Application
,	O
Inc.	O
,	O
Xvid	B-Algorithm
is	O
free	B-Application
software	I-Application
distributed	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>
This	O
also	O
means	O
that	O
unlike	O
the	O
DivX	B-Application
codec	I-Application
,	O
which	O
is	O
only	O
available	O
for	O
a	O
limited	O
number	O
of	O
platforms	O
,	O
Xvid	B-Algorithm
can	O
be	O
used	O
on	O
all	O
platforms	O
and	O
operating	O
systems	O
for	O
which	O
the	O
source	O
code	O
can	O
be	O
compiled	O
.	O
</s>
<s>
In	O
January	O
2001	O
,	O
DivXNetworks	O
founded	O
OpenDivX	B-Algorithm
as	O
part	O
of	O
Project	O
Mayo	O
which	O
was	O
intended	O
to	O
be	O
a	O
home	O
for	O
open	O
source	O
multimedia	O
projects	O
.	O
</s>
<s>
OpenDivX	B-Algorithm
was	O
an	O
open-source	O
MPEG-4	B-Algorithm
video	B-Application
codec	I-Application
based	O
on	O
a	O
stripped-down	O
version	O
of	O
the	O
MoMuSys	O
reference	O
MPEG-4	B-Algorithm
encoder	O
.	O
</s>
<s>
The	O
source	O
code	O
,	O
however	O
,	O
was	O
placed	O
under	O
a	O
restrictive	O
license	O
and	O
only	O
members	O
of	O
the	O
DivX	B-Application
Advanced	O
Research	O
Centre	O
(	O
DARC	O
)	O
had	O
write	O
access	O
to	O
the	O
project	O
's	O
CVS	B-Application
.	O
</s>
<s>
This	O
was	O
updated	O
several	O
times	O
before	O
,	O
in	O
April	O
,	O
it	O
was	O
removed	O
from	O
CVS	B-Application
without	O
warning	O
.	O
</s>
<s>
In	O
July	O
2001	O
,	O
developers	O
started	O
complaining	O
about	O
a	O
lack	O
of	O
activity	O
in	O
the	O
project	O
;	O
the	O
last	O
CVS	B-Application
commit	O
was	O
several	O
months	O
old	O
,	O
bugfixes	O
were	O
being	O
ignored	O
,	O
and	O
promised	O
documentation	O
had	O
not	O
been	O
written	O
.	O
</s>
<s>
Soon	O
after	O
,	O
DARC	O
released	O
a	O
beta	O
version	O
of	O
their	O
closed-source	B-Application
commercial	O
DivX	B-Application
4	O
codec	B-Application
,	O
which	O
was	O
based	O
on	O
encore2	O
,	O
saying	O
that	O
"	O
what	O
the	O
community	O
really	O
wants	O
is	O
a	O
Winamp	B-Application
,	O
not	O
a	O
Linux.	O
"	O
</s>
<s>
It	O
was	O
after	O
this	O
that	O
a	O
fork	B-Application
of	O
OpenDivX	B-Algorithm
was	O
created	O
,	O
using	O
the	O
latest	O
version	O
of	O
encore2	O
that	O
was	O
downloaded	O
before	O
it	O
was	O
removed	O
.	O
</s>
<s>
Since	O
then	O
,	O
all	O
the	O
OpenDivX	B-Algorithm
code	O
has	O
been	O
replaced	O
and	O
Xvid	B-Algorithm
has	O
been	O
published	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
As	O
an	O
implementation	O
of	O
MPEG-4	B-Application
Part	I-Application
2	I-Application
,	O
Xvid	B-Algorithm
uses	O
many	O
patented	O
technologies	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
Xvid	B-Algorithm
0.9.x	O
versions	O
were	O
not	O
licensed	O
in	O
countries	O
where	O
these	O
software	O
patents	O
are	O
recognized	O
.	O
</s>
<s>
With	O
the	O
1.0.x	O
releases	O
,	O
a	O
GNU	B-License
GPL	I-License
v2	O
license	O
is	O
used	O
with	O
no	O
explicit	O
geographical	O
restriction	O
.	O
</s>
<s>
However	O
,	O
the	O
legal	O
usage	O
of	O
Xvid	B-Algorithm
may	O
still	O
be	O
restricted	O
by	O
local	O
laws	O
.	O
</s>
<s>
In	O
July	O
2002	O
,	O
Sigma	O
Designs	O
released	O
an	O
MPEG-4	B-Algorithm
video	B-Application
codec	I-Application
called	O
the	O
REALmagic	O
MPEG-4	B-Algorithm
Video	B-Application
Codec	I-Application
.	O
</s>
<s>
Before	O
long	O
,	O
people	O
testing	O
this	O
new	O
codec	B-Application
found	O
that	O
it	O
contained	O
considerable	O
portions	O
of	O
Xvid	B-Algorithm
code	O
.	O
</s>
<s>
Sigma	O
Designs	O
was	O
contacted	O
and	O
confirmed	O
that	O
a	O
programmer	O
had	O
based	O
REALmagic	O
on	O
Xvid	B-Algorithm
,	O
but	O
assured	O
that	O
all	O
GPL	B-License
code	O
would	O
be	O
replaced	O
to	O
avoid	O
copyright	O
infringement	O
.	O
</s>
<s>
When	O
Sigma	O
Designs	O
released	O
the	O
supposedly	O
rewritten	O
REALmagic	O
codec	B-Application
,	O
the	O
Xvid	B-Algorithm
developers	O
immediately	O
disassembled	O
it	O
and	O
concluded	O
that	O
it	O
still	O
contained	O
Xvid	B-Algorithm
code	O
,	O
only	O
rearranged	O
in	O
an	O
attempt	O
to	O
disguise	O
its	O
presence	O
.	O
</s>
<s>
The	O
Xvid	B-Algorithm
developers	O
decided	O
to	O
stop	O
work	O
and	O
go	O
public	O
to	O
force	O
Sigma	O
Designs	O
to	O
respect	O
the	O
terms	O
of	O
the	O
GPL	B-License
.	O
</s>
<s>
Xvid	B-Algorithm
is	O
not	O
a	O
video	B-Algorithm
format	I-Algorithm
;	O
it	O
is	O
a	O
program	O
for	O
compressing	O
to	O
and	O
decompressing	O
from	O
(	O
hence	O
the	O
name	O
codec	B-Application
)	O
the	O
MPEG-4	B-Application
ASP	I-Application
format	O
.	O
</s>
<s>
Since	O
Xvid	B-Algorithm
uses	O
MPEG-4	B-Algorithm
Advanced	O
Simple	O
Profile	O
(	O
ASP	O
)	O
compression	O
,	O
video	O
encoded	O
with	O
Xvid	B-Algorithm
is	O
MPEG-4	B-Application
ASP	I-Application
video	O
(	O
not	O
"	O
Xvid	B-Algorithm
video	O
"	O
)	O
,	O
and	O
can	O
therefore	O
theoretically	O
be	O
decoded	O
with	O
all	O
ASP-compliant	O
decoders	O
.	O
</s>
<s>
This	O
includes	O
a	O
large	O
number	O
of	O
media	O
players	O
and	O
decoders	O
based	O
on	O
libavcodec	B-Language
(	O
such	O
as	O
MPlayer	B-Application
,	O
VLC	B-Application
,	O
ffdshow	B-Language
or	O
Perian	B-Operating_System
)	O
.	O
</s>
<s>
,	O
xvid.com	O
carries	O
binaries	O
for	O
using	O
the	O
codec	B-Application
.	O
</s>
<s>
However	O
,	O
early	O
versions	O
of	O
the	O
codec	B-Application
had	O
a	O
bug	O
that	O
prevented	O
XviD-encoded	O
files	O
from	O
being	O
decoded	O
with	O
DivX	B-Application
,	O
even	O
when	O
they	O
were	O
encoded	O
using	O
the	O
DivX	B-Application
fourcc	O
.	O
</s>
<s>
Xvid	B-Algorithm
encoded	O
files	O
can	O
be	O
written	O
to	O
a	O
CD	B-Device
or	O
DVD	O
and	O
played	O
in	O
some	O
(	O
but	O
not	O
all	O
)	O
DivX	B-Application
compatible	O
DVD	B-Device
players	I-Device
and	O
media	O
players	O
.	O
</s>
<s>
However	O
,	O
Xvid	B-Algorithm
can	O
optionally	O
encode	O
video	O
with	O
advanced	O
MPEG-4	B-Algorithm
features	O
that	O
most	O
DivX	B-Application
Certified	O
set-top	O
players	O
do	O
not	O
support	O
.	O
</s>
<s>
Files	O
encoded	O
with	O
global	B-Algorithm
motion	I-Algorithm
compensation	I-Algorithm
,	O
Qpel	B-Algorithm
,	O
MPEG	O
quantization	B-Algorithm
,	O
multiple	O
B-frames	O
or	O
files	O
that	O
exceed	O
the	O
Video	O
buffering	O
verifier	O
limitations	O
may	O
not	O
play	O
back	O
properly	O
on	O
DivX	B-Application
Certified	O
hardware	O
devices	O
.	O
</s>
<s>
For	O
example	O
,	O
Xvid	B-Algorithm
specifies	O
three	O
warp	O
points	O
for	O
its	O
implementation	O
of	O
global	B-Algorithm
motion	I-Algorithm
compensation	I-Algorithm
as	O
opposed	O
to	O
the	O
single	O
warp	O
point	O
implementation	O
of	O
DivX	B-Application
.	O
</s>
<s>
Some	O
issues	O
exist	O
with	O
the	O
custom	O
quantization	B-Algorithm
matrices	I-Algorithm
used	O
in	O
tools	O
such	O
as	O
AutoGK	O
that	O
automate	O
encoding	O
with	O
Xvid	B-Algorithm
.	O
</s>
<s>
However	O
,	O
most	O
recent	O
model	O
DivX	B-Application
compatible	O
DVD	B-Device
players	I-Device
have	O
improved	O
support	O
for	O
custom	O
quantization	B-Algorithm
matrices	I-Algorithm
.	O
</s>
<s>
Operating	O
systems	O
Software	O
Comment	O
Windows	B-Application
VirtualDub	B-Application
,	O
DVDx	O
,	O
xvid	B-Algorithm
encraw	O
,	O
AutoGK	O
,	O
MeGUI	O
etc	O
.	O
</s>
<s>
And	O
all	O
other	O
applications	O
that	O
support	O
encoding	O
through	O
the	O
VfW	B-Device
framework	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
Linux	B-Application
,	O
BSD	B-Operating_System
,	O
and	O
Windows	B-Application
MEncoder	B-Language
,	O
Avidemux	B-Language
,	O
VLC	B-Application
,	O
WinFF	O
(	O
graphical	O
front-end	O
based	O
on	O
FFmpeg	B-Library
)	O
,	O
etc	O
.	O
</s>
<s>
These	O
platform	O
and	O
framework	O
independent	O
applications	O
access	O
the	O
Xvid	B-Algorithm
library	B-Library
directly	O
.	O
</s>
