<s>
In	O
video	O
compression	B-General_Concept
algorithms	I-General_Concept
a	O
residual	B-General_Concept
frame	I-General_Concept
is	O
formed	O
by	O
subtracting	O
the	O
reference	B-General_Concept
frame	I-General_Concept
from	O
the	O
desired	O
frame	O
.	O
</s>
<s>
This	O
difference	O
is	O
known	O
as	O
the	O
error	O
or	O
residual	B-General_Concept
frame	I-General_Concept
.	O
</s>
<s>
The	O
residual	B-General_Concept
frame	I-General_Concept
normally	O
has	O
less	O
information	O
entropy	O
,	O
due	O
to	O
nearby	O
video	O
frames	O
having	O
similarities	O
,	O
and	O
therefore	O
requires	O
fewer	O
bits	O
to	O
compress	O
.	O
</s>
<s>
An	O
encoder	B-General_Concept
will	O
use	O
various	O
algorithms	O
such	O
as	O
motion	B-Algorithm
estimation	I-Algorithm
to	O
construct	O
a	O
frame	O
that	O
describes	O
the	O
differences	O
.	O
</s>
<s>
This	O
allows	O
a	O
decoder	B-General_Concept
to	O
use	O
the	O
reference	B-General_Concept
frame	I-General_Concept
plus	O
the	O
differences	O
to	O
construct	O
the	O
desired	O
frame	O
.	O
</s>
