<s>
RealVideo	B-Algorithm
,	O
or	O
also	O
spelled	O
as	O
Real	B-Algorithm
Video	I-Algorithm
,	O
is	O
a	O
suite	O
of	O
proprietary	B-Application
video	B-Algorithm
compression	I-Algorithm
formats	I-Algorithm
developed	O
by	O
RealNetworks	O
—	O
the	O
specific	O
format	O
changes	O
with	O
the	O
version	O
.	O
</s>
<s>
RealVideo	B-Algorithm
is	O
supported	O
on	O
many	O
platforms	O
,	O
including	O
Windows	B-Application
,	O
Mac	B-Device
,	O
Linux	B-Application
,	O
Solaris	O
,	O
and	O
several	O
mobile	O
phones	O
.	O
</s>
<s>
RealVideo	B-Algorithm
is	O
usually	O
paired	O
with	O
RealAudio	B-Algorithm
and	O
packaged	O
in	O
a	O
RealMedia	O
(	O
.rm	O
)	O
container	O
.	O
</s>
<s>
The	O
first	O
version	O
of	O
RealVideo	B-Algorithm
was	O
announced	O
in	O
1997	O
and	O
was	O
based	O
on	O
the	O
H.263	B-Algorithm
format	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
RealNetworks	O
issued	O
a	O
press	O
release	O
saying	O
they	O
had	O
licensed	O
Iterated	O
Systems	O
 '	O
ClearVideo	O
technology	O
and	O
were	O
including	O
it	O
as	O
the	O
RealVideo	B-Algorithm
Fractal	O
Codec	O
.	O
</s>
<s>
However	O
,	O
support	O
for	O
ClearVideo	O
quietly	O
disappeared	O
in	O
the	O
next	O
version	O
of	O
RealVideo	B-Algorithm
.	O
</s>
<s>
RealVideo	B-Algorithm
continued	O
to	O
use	O
H.263	B-Algorithm
until	O
RealVideo	B-Algorithm
8	O
,	O
when	O
the	O
company	O
switched	O
to	O
a	O
proprietary	B-Application
video	O
format	O
.	O
</s>
<s>
RealVideo	B-Algorithm
codecs	O
are	O
identified	O
by	O
four-character	B-Application
codes	I-Application
.	O
</s>
<s>
RV10	O
and	O
RV20	O
are	O
the	O
H.263-based	O
codecs	O
.	O
</s>
<s>
RV30	O
and	O
RV40	O
are	O
RealNetworks	O
 '	O
proprietary	B-Application
H.264-based	O
codecs	O
.	O
</s>
<s>
These	O
identifiers	O
have	O
been	O
the	O
source	O
of	O
some	O
confusion	O
,	O
as	O
people	O
may	O
assume	O
that	O
RV10	O
is	O
RealVideo	B-Algorithm
version	O
10	O
,	O
when	O
it	O
is	O
actually	O
the	O
first	O
version	O
of	O
RealVideo	B-Algorithm
.	O
</s>
<s>
RealVideo	B-Algorithm
10	O
uses	O
RV40	O
.	O
</s>
<s>
RealVideo	B-Algorithm
can	O
be	O
played	O
from	O
a	O
RealMedia	O
file	O
or	O
streamed	O
over	O
the	O
network	O
using	O
the	O
Real	B-Protocol
Time	I-Protocol
Streaming	I-Protocol
Protocol	I-Protocol
(	O
RTSP	B-Protocol
)	O
,	O
a	O
standard	O
protocol	O
for	O
streaming	O
media	O
developed	O
by	O
the	O
IETF	O
.	O
</s>
<s>
However	O
,	O
RealNetworks	O
uses	O
RTSP	B-Protocol
only	O
to	O
set	O
up	O
and	O
manage	O
the	O
connection	O
.	O
</s>
<s>
The	O
actual	O
video	O
data	O
is	O
sent	O
with	O
their	O
own	O
proprietary	B-Application
Real	B-Protocol
Data	I-Protocol
Transport	I-Protocol
(	O
RDT	O
)	O
protocol	O
.	O
</s>
<s>
This	O
tactic	O
has	O
drawn	O
criticism	O
because	O
it	O
made	O
it	O
difficult	O
to	O
use	O
RealVideo	B-Algorithm
with	O
other	O
player	O
and	O
server	O
software	O
.	O
</s>
<s>
However	O
,	O
the	O
open	B-License
source	I-License
MPlayer	B-Application
project	O
has	O
now	O
developed	O
software	O
capable	O
of	O
playing	O
the	O
RDT	O
streams	O
.	O
</s>
<s>
To	O
facilitate	O
real-time	O
streaming	O
,	O
RealVideo	B-Algorithm
(	O
and	O
RealAudio	B-Algorithm
)	O
normally	O
uses	O
constant	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
encoding	O
,	O
so	O
that	O
the	O
same	O
amount	O
of	O
data	O
is	O
sent	O
over	O
the	O
network	O
each	O
second	O
.	O
</s>
<s>
Recently	O
,	O
RealNetworks	O
has	O
introduced	O
a	O
variable	B-General_Concept
bit	I-General_Concept
rate	I-General_Concept
form	O
called	O
RealMedia	O
Variable	B-General_Concept
Bitrate	I-General_Concept
(	O
RMVB	O
)	O
.	O
</s>
<s>
RealNetworks	O
says	O
that	O
the	O
RealVideo	B-Algorithm
and	O
RealAudio	B-Algorithm
codecs	O
are	O
not	O
available	O
in	O
source	O
code	O
under	O
the	O
RPSL	B-License
license	O
.	O
</s>
<s>
Source	O
code	O
is	O
available	O
only	O
under	O
RCSL	B-License
license	O
for	O
commercial	O
porting	O
to	O
non-supported	O
processors	O
and	O
operating	O
systems	O
.	O
</s>
<s>
While	O
RealNetworks	O
owns	O
most	O
of	O
the	O
intellectual	O
property	O
for	O
RealVideo	B-Algorithm
and	O
RealAudio	B-Algorithm
,	O
RealNetworks	O
has	O
licensed	O
third	O
party	O
technology	O
for	O
certain	O
aspects	O
of	O
those	O
codecs	O
.	O
</s>
<s>
RealNetworks	O
claims	O
that	O
it	O
does	O
not	O
have	O
the	O
rights	O
to	O
license	O
that	O
technology	O
under	O
an	O
open	B-License
source	I-License
license	O
.	O
</s>
<s>
The	O
official	O
player	O
for	O
RealVideo	B-Algorithm
is	O
RealNetworks	O
RealPlayer	B-Application
SP	I-Application
,	O
currently	O
at	O
version	O
15	O
,	O
and	O
is	O
available	O
for	O
various	O
platforms	O
including	O
Windows	B-Application
,	O
Macintosh	B-Device
,	O
and	O
Linux	B-Application
.	O
</s>
<s>
Several	O
other	O
players	O
exist	O
,	O
including	O
MPlayer	B-Application
and	O
Media	B-Language
Player	I-Language
Classic	I-Language
.	O
</s>
<s>
Many	O
of	O
these	O
rely	O
on	O
the	O
dynamically	O
linked	O
libraries	O
(	O
DLLs	O
)	O
from	O
the	O
official	O
RealPlayer	B-Application
to	O
play	O
the	O
video	O
,	O
and	O
thus	O
require	O
RealPlayer	B-Application
to	O
be	O
installed	O
(	O
or	O
at	O
least	O
its	O
DLLs	O
,	O
if	O
not	O
the	O
actual	O
player	O
)	O
.	O
</s>
<s>
However	O
,	O
FFmpeg	B-Library
's	O
libav*	O
libraries	O
(	O
and	O
its	O
DirectShow	B-Library
counterpart	O
ffdshow	B-Language
)	O
can	O
play	O
RealVideo	B-Algorithm
and	O
do	O
not	O
require	O
RealPlayer	B-Application
or	O
any	O
parts	O
thereof	O
.	O
</s>
<s>
The	O
latest	O
version	O
of	O
RealPlayer	B-Application
that	O
can	O
run	O
on	O
Windows	B-Application
9x	O
is	O
RealPlayer	B-Application
8	O
;	O
but	O
this	O
version	O
can	O
be	O
easily	O
modified	O
to	O
play	O
RealPlayer	B-Application
9	O
and	O
10	O
files	O
,	O
by	O
the	O
manual	O
addition	O
of	O
just	O
three	O
.dll	O
files	O
(	O
codecs	O
and	O
plugins	O
)	O
,	O
from	O
Microsoft	O
's	O
free	O
distribution	O
of	O
RealPlayer	B-Application
10	O
,	O
that	O
are	O
not	O
included	O
in	O
RealPlayer	B-Application
8	O
Basic	O
.	O
</s>
<s>
RealNetworks	O
has	O
also	O
developed	O
the	O
open	B-License
source	I-License
Helix	B-Application
player	I-Application
,	O
however	O
support	O
for	O
RealVideo	B-Algorithm
in	O
the	O
Helix	B-Application
Project	I-Application
is	O
limited	O
because	O
RealNetworks	O
is	O
still	O
keeping	O
the	O
codecs	O
proprietary	B-Application
.	O
</s>
<s>
RealPlayer	B-Application
does	O
not	O
record	O
RealVideo	B-Algorithm
streams	O
,	O
and	O
RealNetworks	O
has	O
advertised	O
this	O
feature	O
to	O
content	O
owners	O
such	O
as	O
broadcasters	O
,	O
film	O
studios	O
,	O
and	O
music	O
labels	O
,	O
as	O
a	O
means	O
of	O
discouraging	O
users	O
from	O
copying	O
video	O
.	O
</s>
<s>
Such	O
copying	O
,	O
known	O
as	O
time-shifting	B-Device
,	O
is	O
legal	O
in	O
most	O
countries	O
.	O
</s>
<s>
RealVideo	B-Algorithm
files	O
are	O
compressed	O
using	O
several	O
different	O
video	B-Algorithm
compression	I-Algorithm
formats	I-Algorithm
.	O
</s>
<s>
Each	O
video	B-Algorithm
compression	I-Algorithm
format	I-Algorithm
is	O
identified	O
by	O
a	O
four	B-Application
character	I-Application
code	I-Application
.	O
</s>
<s>
Below	O
is	O
a	O
list	O
of	O
the	O
video	B-Algorithm
compression	I-Algorithm
formats	I-Algorithm
and	O
the	O
version	O
in	O
which	O
each	O
was	O
introduced	O
:	O
</s>
<s>
:	O
RealVideo	B-Algorithm
G2	O
and	O
RealVideo	B-Algorithm
G2+SVT	O
,	O
also	O
based	O
on	O
h.263	B-Algorithm
(	O
included	O
with	O
RealPlayer	B-Application
6	O
)	O
.	O
</s>
<s>
:	O
RealVideo	B-Algorithm
10	O
,	O
aka	O
RV9	O
EHQ	O
(	O
included	O
with	O
RealPlayer	B-Application
10	O
)	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
it	O
uses	O
the	O
same	O
FourCC	B-Application
.	O
</s>
<s>
:	O
RealMedia	O
HD	O
(	O
RealVideo	B-Algorithm
11	O
)	O
,	O
suspected	O
to	O
be	O
based	O
on	O
HEVC	B-Algorithm
(	O
included	O
with	O
RealPlayer	B-Application
18	O
)	O
.	O
</s>
<s>
Their	O
tests	O
compared	O
RealMedia	O
HD	O
to	O
HEVC	B-Algorithm
,	O
H.264	B-Application
and	O
VP9	O
encoders	O
.	O
</s>
<s>
Results	O
claimed	O
RealMedia	O
HD	O
provided	O
higher	O
compression	O
than	O
HEVC	B-Algorithm
at	O
higher	O
perceived	O
quality	O
levels	O
.	O
</s>
<s>
The	O
newest	O
version	O
of	O
RealPlayer	B-Application
can	O
play	O
any	O
RealVideo	B-Algorithm
file	O
,	O
as	O
can	O
programs	O
using	O
FFmpeg	B-Library
.	O
</s>
<s>
Other	O
programs	O
may	O
not	O
support	O
all	O
video	B-Algorithm
compression	I-Algorithm
formats	I-Algorithm
.	O
</s>
<s>
In	O
addition	O
to	O
decoder	O
code	O
for	O
up	O
to	O
RV50	O
,	O
FFmpeg	B-Library
also	O
contains	O
open-source	B-License
code	O
for	O
RV10	O
and	O
RV20	O
encoders	O
.	O
</s>
