<s>
Arbitrary	B-General_Concept
slice	I-General_Concept
ordering	I-General_Concept
(	O
ASO	O
)	O
in	O
digital	O
video	O
,	O
is	O
an	O
algorithm	O
for	O
loss	O
prevention	O
.	O
</s>
<s>
It	O
is	O
used	O
for	O
restructuring	O
the	O
ordering	O
of	O
the	O
representation	O
of	O
the	O
fundamental	O
regions	O
(	O
macroblocks	B-General_Concept
)	O
in	O
pictures	O
.	O
</s>
<s>
This	O
type	O
of	O
algorithm	O
is	O
included	O
as	O
tool	O
in	O
baseline	O
profile	O
the	O
H.264/MPEG	B-Application
-4	I-Application
AVC	I-Application
encoder	O
with	O
I	O
Slices	O
,	O
P	O
Slices	O
,	O
Context	O
Adaptative	O
Variable	O
Length	O
Coding	O
(	O
CAVLC	B-Algorithm
)	O
,	O
grouping	O
of	O
slices	O
(	O
Slice	O
Group	O
)	O
,	O
arbitrary	O
slice	O
order	O
(	O
ASO	O
)	O
and	O
Redundancy	O
slices	O
.	O
</s>
<s>
Primarily	O
for	O
lower-cost	O
applications	O
with	O
limited	O
computing	O
resources	O
,	O
this	O
profile	O
is	O
used	O
widely	O
in	O
videoconferencing	B-Application
,	O
mobile	O
applications	O
and	O
security	O
applications	O
also	O
.	O
</s>
<s>
Arbitrary	B-General_Concept
Slice	I-General_Concept
Ordering	I-General_Concept
(	O
ASO	O
)	O
relaxes	O
the	O
constraint	O
that	O
all	O
macroblocks	B-General_Concept
must	O
be	O
sequenced	O
in	O
decoding	O
order	O
,	O
and	O
thus	O
enhances	O
flexibility	O
for	O
low-delay	O
performance	O
important	O
in	O
teleconferencing	O
applications	O
and	O
interactive	O
Internet	O
applications	O
.	O
</s>
<s>
Because	O
Flexible	O
Macroblock	B-General_Concept
Order	O
FMO	B-General_Concept
extend	O
the	O
concept	O
of	O
slices	O
by	O
allowing	O
non-consecutive	O
macroblocks	B-General_Concept
to	O
belong	O
to	O
the	O
same	O
slice	O
,	O
this	O
section	O
also	O
addresses	O
the	O
decoder	O
complexity	O
introduced	O
by	O
(	O
FMO	B-General_Concept
)	O
.	O
</s>
<s>
An	O
example	O
of	O
how	O
macroblocks	B-General_Concept
can	O
be	O
associated	O
to	O
different	O
slices	O
is	O
shown	O
in	O
Figure	O
1	O
.	O
</s>
<s>
Figure	O
1	O
:	O
An	O
example	O
of	O
macroblock	B-General_Concept
assignment	O
to	O
four	O
slices	O
.	O
</s>
<s>
For	O
each	O
slice	O
,	O
the	O
slice	O
length	O
and	O
the	O
macroblock	B-General_Concept
address	O
(	O
i.e.	O
</s>
<s>
index	O
with	O
respect	O
to	O
the	O
raster	O
scan	O
order	O
)	O
of	O
the	O
first	O
macroblock	B-General_Concept
(	O
MB	O
)	O
of	O
the	O
slice	O
are	O
extracted	O
by	O
the	O
slice	O
parser	O
(	O
Figure	O
2	O
)	O
.	O
</s>
<s>
The	O
list	O
of	O
pointers	O
,	O
together	O
with	O
the	O
address	O
of	O
the	O
first	O
macroblock	B-General_Concept
of	O
the	O
slice	O
,	O
will	O
be	O
used	O
to	O
navigate	O
through	O
the	O
out	O
of	O
order	O
slices	O
.	O
</s>
<s>
When	O
ASO	O
and	O
FMO	B-General_Concept
are	O
supported	O
,	O
the	O
four	O
slices	O
of	O
this	O
example	O
can	O
be	O
received	O
by	O
the	O
decoder	O
in	O
a	O
random	O
order	O
.	O
</s>
<s>
The	O
same	O
figure	O
presents	O
the	O
AVC	O
decoder	O
blocks	O
required	O
to	O
support	O
ASO	O
and	O
FMO	B-General_Concept
decoding	O
.	O
</s>
<s>
Figure	O
3	O
:	O
An	O
example	O
of	O
macroblock	B-General_Concept
assignment	O
to	O
four	O
slices	O
and	O
to	O
two	O
Slice	O
Group	O
(	O
SG	O
in	O
the	O
figure	O
)	O
.	O
</s>
<s>
Figure	O
4	O
:	O
The	O
AVC	O
decoder	O
blocks	O
need	O
to	O
support	O
ASO	O
and	O
FMO	B-General_Concept
decoding	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
slice	O
length	O
and	O
the	O
macroblock	B-General_Concept
address	O
of	O
the	O
1st	O
macroblock	B-General_Concept
(	O
MB	O
)	O
of	O
the	O
slice	O
,	O
the	O
slice	O
parser	O
(	O
Figure	O
4	O
)	O
need	O
to	O
extract	O
the	O
Slice	O
Group	O
(	O
SG	O
)	O
of	O
each	O
slice	O
.	O
</s>
<s>
Similarly	O
to	O
the	O
ASO	O
case	O
,	O
in	O
the	O
combined	O
ASO	O
and	O
FMO	B-General_Concept
case	O
the	O
decoder	O
may	O
:	O
</s>
<s>
Because	O
of	O
FMO	B-General_Concept
,	O
decoding	O
macroblocks	B-General_Concept
in	O
raster	O
scan	O
order	O
may	O
require	O
to	O
switch	O
between	O
different	O
slices	O
and/or	O
slice	O
groups	O
.	O
</s>
<s>
In	O
the	O
worst	O
case	O
,	O
swapping	O
occurs	O
after	O
decoding	O
each	O
macroblock	B-General_Concept
.	O
</s>
