<s>
Smart	B-Algorithm
Bitrate	I-Algorithm
Control	I-Algorithm
,	O
commonly	O
referred	O
to	O
as	O
SBC	O
,	O
was	O
a	O
technique	O
for	O
achieving	O
greatly	O
improved	O
video	O
compression	O
efficiency	O
using	O
the	O
DivX	B-Application
3.11	O
Alpha	O
video	B-Application
codec	I-Application
or	O
Microsoft	O
's	O
proprietary	O
MPEG4v2	O
video	B-Application
codec	I-Application
and	O
the	O
Nandub	B-Application
video	O
encoder	O
.	O
</s>
<s>
SBC	O
relied	O
on	O
two	O
main	O
technologies	O
to	O
achieve	O
this	O
improved	O
efficiency	O
:	O
Multipass	O
encoding	O
and	O
Variable	O
Keyframe	B-General_Concept
Intervals	O
(	O
VKI	O
)	O
.	O
</s>
<s>
SBC	O
ceased	O
to	O
be	O
commonly	O
used	O
after	O
XviD	B-Algorithm
and	O
DivX	B-Application
development	O
progressed	O
to	O
a	O
point	O
where	O
they	O
incorporated	O
the	O
same	O
features	O
that	O
SBC	O
pioneered	O
and	O
could	O
offer	O
even	O
more	O
efficient	O
video	O
compression	O
without	O
the	O
need	O
for	O
a	O
specialized	O
application	O
.	O
</s>
<s>
Files	O
created	O
by	O
SBC	O
are	O
compatible	O
with	O
DivX	B-Application
3.11	O
Alpha	O
and	O
can	O
be	O
decoded	O
by	O
most	O
codecs	O
that	O
support	O
ISO	O
MPEG4	O
video	O
.	O
</s>
<s>
The	O
DivX	B-Application
3.11	O
Alpha	O
codec	O
allowed	O
a	O
user	O
to	O
control	O
three	O
aspects	O
of	O
the	O
encoding	O
process	O
:	O
the	O
average	B-General_Concept
bitrate	I-General_Concept
,	O
keyframe	B-General_Concept
interval	O
,	O
and	O
whether	O
the	O
codec	O
preserved	O
smoother	O
motion	O
or	O
more	O
detailed	O
images	O
.	O
</s>
<s>
DivX	B-Application
attempted	O
to	O
encode	O
an	O
entire	O
movie	O
at	O
an	O
average	B-General_Concept
bitrate	I-General_Concept
the	O
user	O
specified	O
,	O
varying	O
the	O
quality	O
of	O
the	O
video	O
in	O
order	O
to	O
achieve	O
the	O
target	O
bitrate	O
.	O
</s>
<s>
DivX	B-Application
's	O
keyframe	B-General_Concept
placement	O
was	O
also	O
very	O
simplistic	O
,	O
it	O
would	O
place	O
keyframes	O
only	O
on	O
the	O
interval	O
that	O
the	O
user	O
selected	O
,	O
every	O
300	O
frames	O
(	O
10	O
seconds	O
at	O
30	O
frame/s	O
)	O
by	O
default	O
.	O
</s>
<s>
Nandub	B-Application
's	O
multipass	O
encoding	O
encoded	O
the	O
video	O
twice	O
;	O
in	O
the	O
first	O
pass	O
it	O
would	O
analyze	O
the	O
video	O
(	O
and	O
write	O
information	O
to	O
a	O
log	O
file	O
)	O
,	O
in	O
the	O
second	O
it	O
would	O
actually	O
produce	O
the	O
output	O
file	O
.	O
</s>
<s>
Instead	O
of	O
varying	O
the	O
image	O
quality	O
to	O
achieve	O
an	O
average	B-General_Concept
bitrate	I-General_Concept
,	O
this	O
allowed	O
SBC	O
to	O
vary	O
the	O
bitrate	O
to	O
achieve	O
an	O
average	O
quality	O
,	O
using	O
higher	O
bitrate	O
for	O
more	O
complex	O
scenes	O
and	O
lower	O
bitrate	O
for	O
simpler	O
scenes	O
.	O
</s>
<s>
A	O
VKI	O
patch	O
(	O
called	O
the	O
DivX	B-Application
Scene	O
Detect	O
Patch	O
)	O
was	O
also	O
available	O
for	O
DivX	B-Application
to	O
allow	O
for	O
VKI	O
functionality	O
without	O
using	O
Nandub	B-Application
,	O
but	O
it	O
offered	O
inferior	O
performance	O
compared	O
to	O
the	O
VKI	O
algorithms	O
included	O
in	O
Nandub	B-Application
.	O
</s>
<s>
Nandub	B-Application
was	O
a	O
modification	O
of	O
the	O
Open	B-License
Source	I-License
VirtualDub	B-Application
video	O
encoder	O
performed	O
by	O
Nando	O
that	O
incorporated	O
SBC	O
features	O
.	O
</s>
