<s>
Theora	B-Algorithm
is	O
a	O
free	O
lossy	B-Algorithm
video	B-Algorithm
compression	I-Algorithm
format	I-Algorithm
.	O
</s>
<s>
It	O
is	O
developed	O
by	O
the	O
Xiph.Org	B-Application
Foundation	I-Application
and	O
distributed	O
without	O
licensing	O
fees	O
alongside	O
their	O
other	O
free	O
and	O
open	O
media	O
projects	O
,	O
including	O
the	O
Vorbis	B-Algorithm
audio	O
format	O
and	O
the	O
Ogg	O
container	O
.	O
</s>
<s>
The	O
libtheora	B-Algorithm
video	B-Application
codec	I-Application
is	O
the	O
reference	O
implementation	O
of	O
the	O
Theora	B-Algorithm
video	B-Algorithm
compression	I-Algorithm
format	I-Algorithm
being	O
developed	O
by	O
the	O
Xiph.Org	B-Application
Foundation	I-Application
.	O
</s>
<s>
Theora	B-Algorithm
is	O
derived	O
from	O
the	O
formerly	O
proprietary	B-Application
VP3	B-Algorithm
codec	O
,	O
released	O
into	O
the	O
public	O
domain	O
by	O
On2	B-Application
Technologies	I-Application
.	O
</s>
<s>
It	O
is	O
broadly	O
comparable	O
in	O
design	O
and	O
bitrate	O
efficiency	O
to	O
MPEG-4	B-Application
Part	I-Application
2	I-Application
,	O
early	O
versions	O
of	O
Windows	B-Device
Media	I-Device
Video	I-Device
,	O
and	O
RealVideo	B-Algorithm
while	O
lacking	O
some	O
of	O
the	O
features	O
present	O
in	O
some	O
of	O
these	O
other	O
codecs	O
.	O
</s>
<s>
It	O
is	O
comparable	O
in	O
open	O
standards	O
philosophy	O
to	O
the	O
BBC	O
's	O
Dirac	B-Application
codec	I-Application
.	O
</s>
<s>
Theora	B-Algorithm
is	O
named	O
after	O
Theora	B-Algorithm
Jones	O
,	O
Edison	O
Carter	O
's	O
Controller	O
on	O
the	O
Max	O
Headroom	O
television	O
program	O
.	O
</s>
<s>
Theora	B-Algorithm
is	O
a	O
variable-bitrate	B-General_Concept
,	O
DCT-based	O
video	O
compression	O
scheme	O
.	O
</s>
<s>
Like	O
most	O
common	O
video	B-Application
codecs	I-Application
,	O
Theora	B-Algorithm
also	O
uses	O
chroma	O
subsampling	O
,	O
block-based	O
motion	O
compensation	O
and	O
an	O
8-by-8	O
DCT	B-General_Concept
block	B-General_Concept
.	O
</s>
<s>
Pixels	O
are	O
grouped	O
into	O
various	O
structures	O
,	O
namely	O
blocks	O
,	O
super	O
blocks	O
,	O
and	O
macroblocks	B-General_Concept
.	O
</s>
<s>
Theora	B-Algorithm
supports	O
intra-coded	O
frames	O
and	O
forward-predictive	O
frames	O
,	O
but	O
not	O
bi-predictive	O
frames	O
which	O
are	O
found	O
in	O
H.264	B-Application
and	O
VC-1	B-Operating_System
.	O
</s>
<s>
Theora	B-Algorithm
also	O
does	O
not	O
support	O
interlacing	O
,	O
or	O
bit-depths	O
larger	O
than	O
8	O
bits	O
per	O
component	O
.	O
</s>
<s>
Theora	B-Algorithm
video	O
streams	O
can	O
be	O
stored	O
in	O
any	O
suitable	O
container	O
format	O
,	O
but	O
they	O
are	O
most	O
commonly	O
found	O
in	O
the	O
Ogg	O
container	O
with	O
Vorbis	B-Algorithm
or	O
FLAC	B-Application
audio	O
streams	O
.	O
</s>
<s>
The	O
Theora	B-Algorithm
video-compression	O
format	O
is	O
essentially	O
compatible	O
with	O
the	O
VP3	B-Algorithm
video-compression	O
format	O
,	O
consisting	O
of	O
a	O
backward-compatible	O
superset	O
.	O
</s>
<s>
Theora	B-Algorithm
is	O
a	O
superset	O
of	O
VP3	B-Algorithm
,	O
and	O
VP3	B-Algorithm
streams	O
(	O
with	O
some	O
minor	O
syntactic	O
modifications	O
)	O
can	O
be	O
converted	O
into	O
Theora	B-Algorithm
streams	O
without	O
recompression	O
(	O
but	O
not	O
vice	O
versa	O
)	O
.	O
</s>
<s>
VP3	B-Algorithm
video	O
compression	O
can	O
be	O
decoded	O
using	O
Theora	B-Algorithm
implementations	O
,	O
but	O
Theora	B-Algorithm
video	O
compression	O
usually	O
cannot	O
be	O
decoded	O
using	O
old	O
VP3	B-Algorithm
implementations	O
.	O
</s>
<s>
Theora	B-Algorithm
's	O
predecessor	O
On2	B-Application
TrueMotion	B-Application
VP3	B-Algorithm
was	O
originally	O
a	O
proprietary	B-Application
and	O
patent-encumbered	O
video	B-Application
codec	I-Application
developed	O
by	O
On2	B-Application
Technologies	I-Application
.	O
</s>
<s>
VP3.1	O
was	O
introduced	O
in	O
May	O
2000	O
and	O
followed	O
three	O
months	O
later	O
by	O
the	O
VP3.2	O
release	O
,	O
which	O
is	O
the	O
basis	O
for	O
Theora	B-Algorithm
.	O
</s>
<s>
In	O
August	O
2001	O
,	O
On2	B-Application
Technologies	I-Application
announced	O
that	O
they	O
would	O
be	O
releasing	O
an	O
open	O
source	O
version	O
of	O
their	O
VP3.2	O
video	O
compression	O
algorithm	O
.	O
</s>
<s>
In	O
September	O
2001	O
,	O
On2	B-Application
Technologies	I-Application
published	O
the	O
source	O
code	O
of	O
the	O
VP3.2	O
codec	O
under	O
the	O
VP3.2	O
Public	O
License	O
0.1	O
,	O
a	O
custom	O
open-source	B-Application
license	O
.	O
</s>
<s>
The	O
license	O
only	O
granted	O
the	O
right	O
to	O
modify	O
the	O
source	O
code	O
if	O
the	O
resulting	O
larger	O
work	O
continued	O
to	O
support	O
playback	O
of	O
VP3.2	O
data	O
.	O
</s>
<s>
In	O
March	O
2002	O
,	O
On2	B-Application
responded	O
to	O
the	O
public	O
's	O
reception	O
by	O
relicensing	O
the	O
VP3	B-Algorithm
codec	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
.	O
</s>
<s>
In	O
June	O
2002	O
,	O
On2	B-Application
donated	O
VP3	B-Algorithm
to	O
the	O
Xiph.Org	B-Application
Foundation	I-Application
and	O
offered	O
it	O
under	O
the	O
Ogg	B-Algorithm
Vorbis	I-Algorithm
BSD-style	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
On2	B-Application
also	O
made	O
an	O
irrevocable	O
,	O
royalty-free	O
license	O
grant	O
for	O
any	O
patent	O
claims	O
it	O
might	O
have	O
over	O
the	O
software	O
and	O
any	O
derivatives	O
,	O
allowing	O
anyone	O
to	O
use	O
any	O
VP3-derived	O
codec	O
for	O
any	O
purpose	O
.	O
</s>
<s>
In	O
August	O
2002	O
,	O
On2	B-Application
entered	O
into	O
an	O
agreement	O
with	O
the	O
Xiph.Org	B-Application
Foundation	I-Application
to	O
make	O
VP3	B-Algorithm
the	O
basis	O
of	O
a	O
new	O
,	O
free	O
video	B-Application
codec	I-Application
,	O
called	O
Theora	B-Algorithm
.	O
</s>
<s>
On2	B-Application
declared	O
Theora	B-Algorithm
to	O
be	O
VP3	B-Algorithm
's	O
successor	O
.	O
</s>
<s>
On	O
3	O
October	O
2002	O
,	O
On2	B-Application
and	O
Xiph	B-Application
announced	O
the	O
completion	O
and	O
availability	O
of	O
the	O
initial	O
alpha	O
code	O
release	O
of	O
libtheora	B-Algorithm
,	O
Theora	B-Algorithm
's	O
reference	O
implementation	O
.	O
</s>
<s>
There	O
is	O
no	O
formal	O
specification	O
for	O
VP3	B-Algorithm
's	O
bitstream	B-General_Concept
format	I-General_Concept
beyond	O
the	O
VP3	B-Algorithm
source	O
code	O
published	O
by	O
On2	B-Application
Technologies	I-Application
.	O
</s>
<s>
In	O
2003	O
,	O
Mike	O
Melanson	O
created	O
an	O
incomplete	O
description	O
of	O
the	O
VP3	B-Algorithm
bitstream	B-General_Concept
format	I-General_Concept
and	O
decoding	O
process	O
at	O
a	O
higher	O
level	O
than	O
source	O
code	O
,	O
with	O
some	O
help	O
from	O
On2	B-Application
and	O
Xiph.Org	B-Application
Foundation	I-Application
.	O
</s>
<s>
The	O
Theora	B-Algorithm
specification	O
adopted	O
some	O
portions	O
of	O
this	O
VP3	B-Algorithm
description	O
.	O
</s>
<s>
A	O
successor	O
to	O
Theora	B-Algorithm
,	O
Daala	B-Application
,	O
was	O
later	O
merged	O
into	O
AV1	B-Application
.	O
</s>
<s>
The	O
Theora	B-Algorithm
I	O
bitstream	B-General_Concept
format	I-General_Concept
was	O
frozen	O
in	O
June	O
2004	O
after	O
the	O
libtheora	B-Algorithm
1.0alpha3	O
release	O
.	O
</s>
<s>
Videos	O
encoded	O
with	O
any	O
version	O
of	O
the	O
libtheora	B-Algorithm
since	O
the	O
alpha3	O
will	O
be	O
compatible	O
with	O
any	O
future	O
player	O
.	O
</s>
<s>
This	O
is	O
also	O
true	O
for	O
videos	O
encoded	O
with	O
any	O
implementation	O
of	O
the	O
Theora	B-Algorithm
I	O
specification	O
since	O
the	O
format	O
freeze	O
.	O
</s>
<s>
The	O
Theora	B-Algorithm
I	O
Specification	O
was	O
completely	O
published	O
in	O
2004	O
.	O
</s>
<s>
The	O
Theora	B-Algorithm
reference	O
implementation	O
libtheora	B-Algorithm
spent	O
several	O
years	O
in	O
alpha	O
and	O
beta	O
status	O
.	O
</s>
<s>
The	O
first	O
stable	O
release	O
of	O
libtheora	B-Algorithm
was	O
made	O
in	O
November	O
2008	O
.	O
</s>
<s>
Work	O
then	O
focused	O
on	O
improving	O
the	O
codec	O
's	O
performance	O
in	O
the	O
"	O
Thusnelda	O
"	O
branch	O
,	O
which	O
was	O
released	O
as	O
version	O
1.1	O
in	O
September	O
2009	O
as	O
the	O
second	O
stable	O
libtheora	B-Algorithm
release	O
.	O
</s>
<s>
The	O
codename	O
for	O
the	O
next	O
version	O
of	O
libtheora	B-Algorithm
is	O
Ptalarbvorm	O
.	O
</s>
<s>
Theora	B-Algorithm
is	O
well	O
established	O
as	O
a	O
video	O
format	O
in	O
open-source	B-Application
applications	I-Application
,	O
and	O
became	O
the	O
format	O
used	O
for	O
Wikipedia	O
's	O
video	O
content	O
before	O
being	O
mostly	O
replaced	O
by	O
VP9	B-Algorithm
.	O
</s>
<s>
However	O
,	O
the	O
proposed	O
adoption	O
of	O
Theora	B-Algorithm
as	O
part	O
of	O
the	O
baseline	O
video	O
support	O
in	O
HTML5	B-Application
resulted	B-Application
in	I-Application
controversy	I-Application
.	O
</s>
<s>
found	O
that	O
their	O
subjective	O
visual	O
quality	O
was	O
inferior	O
to	O
that	O
of	O
contemporary	O
video	B-Application
codecs	I-Application
.	O
</s>
<s>
More	O
recently	O
however	O
,	O
Xiph	B-Application
developers	O
compared	O
the	O
1.1	O
Theora	B-Algorithm
encoder	O
to	O
YouTube	B-General_Concept
's	O
H.264	B-Application
and	O
H.263	O
+	O
encoders	O
,	O
in	O
response	O
to	O
concerns	O
raised	O
in	O
2009	O
about	O
Theora	B-Algorithm
's	O
inferior	O
performance	O
by	O
Chris	O
DiBona	O
,	O
a	O
Google	B-Application
employee	O
.	O
</s>
<s>
They	O
found	O
the	O
results	O
from	O
Theora	B-Algorithm
to	O
be	O
nearly	O
the	O
same	O
as	O
YouTube	B-General_Concept
's	O
H.264	B-Application
output	O
,	O
and	O
much	O
better	O
than	O
the	O
H.263	O
+	O
output	O
.	O
</s>
<s>
The	O
performance	O
characteristics	O
of	O
the	O
Theora	B-Algorithm
1.0	O
reference	O
implementation	O
are	O
dominated	O
mostly	O
by	O
implementation	O
problems	O
inherited	O
from	O
the	O
original	O
VP3	B-Algorithm
code	O
base	O
.	O
</s>
<s>
A	O
May	O
2009	O
review	O
of	O
this	O
work	O
claimed	O
a	O
considerable	O
improvement	O
in	O
quality	O
,	O
both	O
subjectively	O
and	O
as	O
measured	O
by	O
PSNR	O
,	O
just	O
by	O
improving	O
the	O
forward	O
DCT	B-General_Concept
and	O
quantisation	O
matrices	O
.	O
</s>
<s>
A	O
flaw	O
in	O
the	O
version	O
of	O
FFmpeg	B-Library
used	O
in	O
the	O
test	O
initially	O
led	O
to	O
incorrect	O
reports	O
of	O
Theora	B-Algorithm
PSNR	O
surpassing	O
that	O
of	O
H.264	B-Application
.	O
</s>
<s>
The	O
differences	O
in	O
quality	O
,	O
bitrate	O
and	O
file	O
size	O
between	O
a	O
YouTube	B-General_Concept
H.264	B-Application
video	O
and	O
a	O
transcoded	O
Ogg	B-Algorithm
video	I-Algorithm
file	O
are	O
very	O
small	O
.	O
</s>
<s>
There	O
is	O
an	O
open-source	B-Application
VHDL	B-Language
code	O
base	O
for	O
a	O
hardware	O
Theora	B-Algorithm
decoder	O
in	O
development	O
.	O
</s>
<s>
It	O
began	O
as	O
a	O
2006	O
Google	B-Application
Summer	I-Application
of	I-Application
Code	I-Application
project	O
,	O
and	O
it	O
has	O
been	O
developed	O
on	O
both	O
the	O
Nios	B-Device
II	I-Device
and	O
LEON	B-General_Concept
processors	O
.	O
</s>
<s>
However	O
,	O
there	O
are	O
currently	O
no	O
Theora	B-Algorithm
decoder	O
chips	O
in	O
production	O
,	O
and	O
portable	O
media	O
players	O
,	O
smartphones	B-Application
and	O
similar	O
devices	O
with	O
limited	O
computing	O
power	O
rely	O
on	O
such	O
chips	O
to	O
provide	O
efficient	O
playback	O
.	O
</s>
<s>
As	O
originally	O
recommended	O
by	O
HTML	B-Application
5	I-Application
,	O
these	O
browsers	O
support	O
Theora	B-Algorithm
when	O
embedded	O
by	O
the	O
video	O
element	O
:	O
</s>
<s>
Mozilla	B-Language
Firefox	I-Language
3.5	I-Language
and	O
later	O
versions	O
including	O
Firefox	B-Application
for	I-Application
mobile	I-Application
(	O
Fennec	B-Application
)	O
.	O
</s>
<s>
Google	B-Application
Chrome	I-Application
as	O
of	O
version	O
3.0.182.2	O
including	O
Chromium	B-Language
as	O
of	O
14	O
July	O
2009	O
.	O
</s>
<s>
SeaMonkey	B-Language
as	O
of	O
version	O
2.0	O
.	O
</s>
<s>
Opera	B-Application
as	O
of	O
version	O
10.50	O
.	O
</s>
<s>
It	O
was	O
also	O
supported	O
in	O
Opera	B-Application
9.5	O
experimental	O
video	O
builds	O
.	O
</s>
<s>
Web	B-Language
uses	O
WebKitGTK+	O
as	O
its	O
rendering	O
engine	O
.	O
</s>
<s>
As	O
WebKitGTK+	O
uses	O
GStreamer	B-Language
to	O
implement	O
the	O
HTML5	B-Application
media	O
player	O
,	O
and	O
all	O
the	O
formats	O
GStreamer	B-Language
supports	O
(	O
including	O
Theora	B-Algorithm
)	O
are	O
available	O
in	O
browser	O
.	O
</s>
<s>
Midori	B-Protocol
is	O
another	O
example	O
of	O
a	O
browser	O
that	O
supports	O
Theora	B-Algorithm
by	O
using	O
WebKitGTK+	O
.	O
</s>
<s>
GStreamer	B-Language
supported	O
via	O
Theora	B-Algorithm
or	O
FFmpeg	B-Library
module	O
,	O
supports	O
GStreamer	B-Language
based	O
applications	O
e.g.	O
</s>
<s>
Silverlight	B-Application
Highgate	O
media	O
suite	O
is	O
going	O
to	O
bring	O
an	O
Open	O
Source	O
Theora/Vorbis	O
implementation	O
in	O
Silverlight	B-Application
.	O
</s>
<s>
It	O
will	O
enable	O
installation-free	O
support	O
for	O
HTML5	B-Application
streaming	O
video	O
.	O
</s>
<s>
There	O
are	O
several	O
third-party	O
programs	O
that	O
support	O
encoding	O
through	O
libtheora	B-Algorithm
:	O
</s>
<s>
Name	O
Description	O
Operating	O
Systems	O
Supported	O
Unix-like	B-Operating_System
OS	I-Operating_System
X	O
Windows	B-Application
Firefogg	O
A	O
Firefox	B-Application
browser	I-Application
extension	O
implementation	O
of	O
ffmpeg2theora	B-Library
ffmpeg2theora	B-Library
A	O
command-line	O
program	O
that	O
transcodes	O
video	O
by	O
decoding	O
with	O
FFmpeg	B-Library
and	O
reencoding	O
with	O
libtheora	B-Algorithm
to	O
encode	O
it	O
VLC	B-Application
Can	O
transcode	O
to	O
single-pass	O
Theora	B-Algorithm
1.0	O
and	O
optionally	O
stream	O
it	O
OggConvert	B-Language
Transcodes	O
supported	O
media	O
to	O
Vorbis	B-Algorithm
,	O
Theora	B-Algorithm
,	O
or	O
Dirac	B-Application
?	O
</s>
<s>
FreeJ	B-Application
"	O
Video	O
DJing	O
"	O
software	O
that	O
can	O
encode	O
to	O
and	O
stream	O
Theora	B-Algorithm
?	O
</s>
<s>
Kdenlive	B-Language
The	O
video	O
editor	O
supplied	O
with	O
KDE	B-Application
?	O
</s>
<s>
Pitivi	B-Application
The	O
video	O
editor	O
supplied	O
with	O
GNOME	B-Application
?	O
</s>
<s>
LiVES	O
Video	O
editing	O
software	O
for	O
Linux	B-Application
.	O
</s>
<s>
Can	O
edit	O
,	O
encode	O
and	O
stream	O
theora	B-Algorithm
.	O
</s>
<s>
Thoggen	B-Application
A	O
GTK+	O
and	O
GStreamer	B-Language
based	O
DVD	O
backup	O
utility	O
?	O
</s>
<s>
HandBrake	B-Language
Can	O
output	O
to	O
Theora	B-Algorithm
only	O
with	O
the	O
Matroska	O
container	O
RecordMyDesktop	B-Protocol
Records	O
the	O
screen	O
to	O
Ogg	B-Algorithm
Theora	I-Algorithm
with	O
optional	O
Vorbis	B-Algorithm
audio	O
?	O
</s>
<s>
The	O
libtheora	B-Algorithm
library	O
contains	O
the	O
reference	O
implementation	O
of	O
the	O
Theora	B-Algorithm
specification	O
for	O
encoding	O
and	O
decoding	O
.	O
</s>
<s>
libtheora	B-Algorithm
is	O
still	O
under	O
development	O
by	O
the	O
Xiph.Org	B-Application
Foundation	I-Application
.	O
</s>
<s>
The	O
library	O
is	O
released	O
under	O
the	O
terms	O
of	O
a	O
BSD-style	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Also	O
,	O
several	O
media	O
frameworks	O
have	O
support	O
for	O
Theora	B-Algorithm
.	O
</s>
<s>
The	O
open-source	B-Application
ffdshow	B-Language
audio/video	O
decoder	O
is	O
capable	O
of	O
encoding	O
Theora	B-Algorithm
videos	O
using	O
its	O
Video	B-Device
for	I-Device
Windows	I-Device
(	O
VFW	O
)	O
multi-codec	O
interface	O
within	O
popular	O
AVI	O
editing	O
programs	O
.	O
</s>
<s>
It	O
supports	O
both	O
encoding	O
and	O
decoding	O
Theora	B-Algorithm
video	O
streams	O
and	O
uses	O
Theora	B-Algorithm
's	O
alpha	O
4	O
libraries	O
.	O
</s>
<s>
However	O
,	O
many	O
of	O
the	O
more	O
refined	O
features	O
of	O
Theora	B-Algorithm
are	O
n't	O
available	O
to	O
the	O
user	O
in	O
ffdshow	B-Language
's	O
interface	O
.	O
</s>
<s>
Name	O
Description	O
Operating	O
Systems	O
Supported	O
Unix-like	B-Operating_System
OS	I-Operating_System
X	O
Windows	B-Application
LiVES	O
Video	O
editing	O
software	O
for	O
Linux	B-Application
.	O
</s>
<s>
Can	O
edit	O
,	O
encode	O
and	O
stream	O
theora	B-Algorithm
.	O
</s>
<s>
Kdenlive	B-Language
The	O
KDE	B-Application
video	O
editor	O
.	O
</s>
<s>
OpenShot	B-Application
?	O
</s>
<s>
Pitivi	B-Application
The	O
GNOME	B-Application
video	O
editor	O
.	O
</s>
<s>
Cinelerra	B-Language
CVS	B-Application
versions	O
of	O
the	O
Cinelerra	B-Language
non-linear	O
video	O
editing	O
system	O
support	O
Theora	B-Algorithm
,	O
as	O
of	O
August	O
2005	O
.	O
?	O
</s>
<s>
oggz-tools	O
by	O
Xiph.org	B-Application
Command	O
line	O
programs	O
to	O
examine	O
and	O
edit	O
Ogg	O
files	O
.	O
</s>
<s>
Ogg	B-Algorithm
Video	I-Algorithm
Tools	O
by	O
yornstreamnik	O
Tools	O
to	O
resize	O
,	O
cut	O
,	O
split	O
,	O
join	O
,	O
and	O
others	O
AVS	B-Application
Video	I-Application
Editor	I-Application
?	O
</s>
<s>
The	O
following	O
streaming	O
media	O
servers	O
are	O
capable	O
of	O
streaming	O
Theora	B-Algorithm
video	O
:	O
</s>
<s>
Name	O
Description	O
Operating	O
Systems	O
Supported	O
Unix-like	B-Operating_System
OS	I-Operating_System
X	O
Windows	B-Application
VLC	B-Application
Icecast	B-Application
?	O
</s>
<s>
Written	O
in	O
Java	B-Language
?	O
</s>
<s>
LiVES	O
Can	O
stream	O
ogg/theora/vorbis	O
in	O
realtime	O
to	O
a	O
file	O
or	O
fifo	O
.	O
</s>
<s>
Elphel	B-Algorithm
is	O
the	O
main	O
maker	O
of	O
cameras	O
that	O
record	O
in	O
theora	B-Algorithm
.	O
</s>
