<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
(	O
often	O
abbreviated	O
PAR	O
)	O
is	O
a	O
mathematical	O
ratio	O
that	O
describes	O
how	O
the	O
width	O
of	O
a	O
pixel	B-Algorithm
in	O
a	O
digital	B-Algorithm
image	I-Algorithm
compares	O
to	O
the	O
height	O
of	O
that	O
pixel	B-Algorithm
.	O
</s>
<s>
Most	O
digital	B-Algorithm
imaging	I-Algorithm
systems	O
display	O
an	O
image	O
as	O
a	O
grid	O
of	O
tiny	O
,	O
square	B-Device
pixels	I-Device
.	O
</s>
<s>
However	O
,	O
some	O
imaging	O
systems	O
,	O
especially	O
those	O
that	O
must	O
be	O
compatible	O
with	O
standard-definition	B-Device
television	I-Device
motion	O
pictures	O
,	O
display	O
an	O
image	O
as	O
a	O
grid	O
of	O
rectangular	B-Algorithm
pixels	I-Algorithm
,	O
in	O
which	O
the	O
pixel	B-Algorithm
width	O
and	O
height	O
are	O
different	O
.	O
</s>
<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
describes	O
this	O
difference	O
.	O
</s>
<s>
Use	O
of	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
mostly	O
involves	O
pictures	O
pertaining	O
to	O
standard-definition	B-Device
television	I-Device
and	O
some	O
other	O
exceptional	O
cases	O
.	O
</s>
<s>
Most	O
other	O
imaging	O
systems	O
,	O
including	O
those	O
that	O
comply	O
with	O
SMPTE	O
standards	O
and	O
practices	O
,	O
use	O
square	B-Device
pixels	I-Device
.	O
</s>
<s>
PAR	O
is	O
also	O
known	O
as	O
sample	B-Device
aspect	I-Device
ratio	I-Device
and	O
abbreviated	O
SAR	O
,	O
though	O
it	O
can	O
be	O
confused	O
with	O
storage	O
aspect	B-Device
ratio	I-Device
.	O
</s>
<s>
The	O
ratio	O
of	O
the	O
width	O
to	O
the	O
height	O
of	O
an	O
image	O
is	O
known	O
as	O
the	O
aspect	B-Device
ratio	I-Device
,	O
or	O
more	O
precisely	O
the	O
display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
(	O
DAR	O
)	O
–	O
the	O
aspect	B-Device
ratio	I-Device
of	O
the	O
image	O
as	O
displayed	O
;	O
for	O
TV	O
,	O
DAR	O
was	O
traditionally	O
4:3	O
(	O
a.k.a.	O
</s>
<s>
widescreen	O
)	O
now	O
the	O
standard	O
for	O
HDTV	B-Device
.	O
</s>
<s>
In	O
digital	B-Algorithm
images	I-Algorithm
,	O
there	O
is	O
a	O
distinction	O
with	O
the	O
storage	O
aspect	B-Device
ratio	I-Device
(	O
SAR	O
)	O
,	O
which	O
is	O
the	O
ratio	O
of	O
pixel	B-General_Concept
dimensions	I-General_Concept
.	O
</s>
<s>
If	O
an	O
image	O
is	O
displayed	O
with	O
square	B-Device
pixels	I-Device
,	O
then	O
these	O
ratios	O
agree	O
;	O
if	O
not	O
,	O
then	O
non-square	O
,	O
"	O
rectangular	O
"	O
pixels	B-Algorithm
are	O
used	O
,	O
and	O
these	O
ratios	O
disagree	O
.	O
</s>
<s>
The	O
aspect	B-Device
ratio	I-Device
of	O
the	O
pixels	B-Algorithm
themselves	O
is	O
known	O
as	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
(	O
PAR	O
)	O
–	O
for	O
square	B-Device
pixels	I-Device
this	O
is	O
1:1	O
–	O
and	O
these	O
are	O
related	O
by	O
the	O
identity	O
:	O
</s>
<s>
For	O
example	O
,	O
a	O
640480	O
VGA	B-Protocol
image	O
has	O
a	O
SAR	O
of	O
640/480	O
=	O
4:3	O
,	O
and	O
if	O
displayed	O
on	O
a	O
4:3	O
display	O
(	O
DAR	O
=	O
4:3	O
)	O
has	O
square	B-Device
pixels	I-Device
,	O
hence	O
a	O
PAR	O
of	O
1:1	O
.	O
</s>
<s>
By	O
contrast	O
,	O
a	O
720576	O
D-1	O
PAL	B-Language
image	O
has	O
a	O
SAR	O
of	O
720/576	O
=	O
5:4	O
,	O
but	O
is	O
displayed	O
on	O
a	O
4:3	O
display	O
(	O
DAR	O
=	O
4:3	O
)	O
.	O
</s>
<s>
In	O
analog	O
images	O
such	O
as	O
film	O
there	O
is	O
no	O
notion	O
of	O
pixel	B-Algorithm
,	O
nor	O
notion	O
of	O
SAR	O
or	O
PAR	O
,	O
but	O
in	O
the	O
digitization	O
of	O
analog	O
images	O
the	O
resulting	O
digital	B-Algorithm
image	I-Algorithm
has	O
pixels	B-Algorithm
,	O
hence	O
SAR	O
(	O
and	O
accordingly	O
PAR	O
,	O
if	O
displayed	O
at	O
the	O
same	O
aspect	B-Device
ratio	I-Device
as	O
the	O
original	O
)	O
.	O
</s>
<s>
Non-square	O
pixels	O
arise	O
often	O
in	O
early	O
digital	O
TV	O
standards	O
,	O
related	O
to	O
digitalization	O
of	O
analog	O
TV	O
signals	O
–	O
whose	O
vertical	O
and	O
"	O
effective	O
"	O
horizontal	O
resolutions	O
differ	O
and	O
are	O
thus	O
best	O
described	O
by	O
non-square	O
pixels	O
–	O
and	O
also	O
in	O
some	O
digital	O
video	O
cameras	O
and	O
computer	O
display	O
modes	O
,	O
such	O
as	O
Color	B-Device
Graphics	I-Device
Adapter	I-Device
(	O
CGA	B-Device
)	O
.	O
</s>
<s>
Today	O
they	O
arise	O
also	O
in	O
transcoding	B-Algorithm
between	O
resolutions	O
with	O
different	O
SARs	O
.	O
</s>
<s>
Actual	O
displays	O
do	O
not	O
generally	O
have	O
non-square	O
pixels	O
,	O
though	O
digital	O
sensors	O
might	O
;	O
they	O
are	O
rather	O
a	O
mathematical	O
abstraction	O
used	O
in	O
resampling	B-Algorithm
images	O
to	O
convert	O
between	O
resolutions	O
.	O
</s>
<s>
First	O
,	O
analog	O
video	O
does	O
not	O
have	O
pixels	B-Algorithm
,	O
but	O
rather	O
a	O
raster	O
scan	O
,	O
and	O
thus	O
has	O
a	O
well-defined	O
vertical	O
resolution	O
(	O
the	O
lines	O
of	O
the	O
raster	O
)	O
,	O
but	O
not	O
a	O
well-defined	O
horizontal	O
resolution	O
,	O
since	O
each	O
line	B-Application
is	O
an	O
analog	O
signal	O
.	O
</s>
<s>
Third	O
,	O
analog	O
video	B-Application
signals	I-Application
are	O
interlaced	O
–	O
each	O
image	O
(	O
frame	O
)	O
is	O
sent	O
as	O
two	O
"	O
fields	O
"	O
,	O
each	O
with	O
half	O
the	O
lines	O
.	O
</s>
<s>
Thus	O
either	O
the	O
pixels	B-Algorithm
are	O
twice	O
as	O
tall	O
as	O
they	O
would	O
be	O
without	O
interlacing	O
,	O
or	O
the	O
image	O
is	O
deinterlaced	O
.	O
</s>
<s>
As	O
digital	O
display	O
technology	O
,	O
digital	O
broadcast	O
technology	O
,	O
and	O
digital	O
video	O
compression	O
evolved	O
separately	O
,	O
it	O
resulted	O
in	O
video	O
frame	O
differences	O
that	O
must	O
be	O
addressed	O
using	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
.	O
</s>
<s>
Digital	O
video	O
frames	O
are	O
generally	O
defined	O
as	O
a	O
grid	O
of	O
pixels	B-Algorithm
used	O
to	O
present	O
each	O
sequential	O
image	O
.	O
</s>
<s>
The	O
horizontal	O
component	O
is	O
defined	O
by	O
pixels	B-Algorithm
(	O
or	O
samples	O
)	O
,	O
and	O
is	O
known	O
as	O
a	O
video	O
line	B-Application
.	O
</s>
<s>
Standard-definition	B-Device
television	I-Device
standards	O
and	O
practices	O
were	O
developed	O
as	O
broadcast	O
technologies	O
and	O
intended	O
for	O
terrestrial	O
broadcasting	O
,	O
and	O
were	O
therefore	O
not	O
designed	O
for	O
digital	O
video	O
presentation	O
.	O
</s>
<s>
Such	O
standards	O
define	O
an	O
image	O
as	O
an	O
array	O
of	O
well-defined	O
horizontal	O
"	O
Lines	O
"	O
,	O
well-defined	O
vertical	O
"	O
Line	B-Application
Duration	O
"	O
and	O
a	O
well-defined	O
picture	O
center	O
.	O
</s>
<s>
However	O
,	O
there	O
is	O
not	O
a	O
standard-definition	B-Device
television	I-Device
standard	O
that	O
properly	O
defines	O
image	O
edges	O
or	O
explicitly	O
demands	O
a	O
certain	O
number	O
of	O
picture	B-Algorithm
elements	I-Algorithm
per	O
line	B-Application
.	O
</s>
<s>
Furthermore	O
,	O
analog	O
video	O
systems	O
such	O
as	O
NTSC	O
480i	O
and	O
PAL	B-Language
576i	O
,	O
instead	O
of	O
employing	O
progressively	O
displayed	O
frames	O
,	O
employ	O
fields	O
or	O
interlaced	O
half-frames	O
displayed	O
in	O
an	O
interwoven	O
manner	O
to	O
reduce	O
flicker	O
and	O
double	O
the	O
image	O
rate	O
for	O
smoother	O
motion	O
.	O
</s>
<s>
To	O
convert	O
analog	O
video	O
lines	O
into	O
a	O
series	O
of	O
square	B-Device
pixels	I-Device
,	O
the	O
industry	O
adopted	O
a	O
default	O
sampling	O
rate	O
at	O
which	O
luma	O
values	O
were	O
extracted	O
into	O
pixels	B-Algorithm
.	O
</s>
<s>
The	O
term	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
was	O
first	O
coined	O
when	O
ITU-R	O
BT.601	O
(	O
commonly	O
known	O
as	O
"	O
Rec	O
.	O
</s>
<s>
601	O
"	O
)	O
specified	O
that	O
standard-definition	B-Device
television	I-Device
pictures	O
are	O
made	O
of	O
lines	O
of	O
exactly	O
720	O
non-square	O
pixels	O
.	O
</s>
<s>
ITU-R	O
BT.601	O
did	O
not	O
define	O
the	O
exact	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
but	O
did	O
provide	O
enough	O
information	O
to	O
calculate	O
the	O
exact	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
based	O
on	O
industry	O
practices	O
:	O
The	O
standard	O
luma	O
sampling	O
rate	O
of	O
precisely	O
MHz	O
.	O
</s>
<s>
The	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
for	O
480i	O
would	O
be	O
10:11	O
as	O
:	O
</s>
<s>
The	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
for	O
576i	O
would	O
be	O
59:54	O
as	O
:	O
</s>
<s>
SMPTE	O
RP	O
187	O
further	O
attempted	O
to	O
standardize	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
values	O
for	O
480i	O
and	O
576i	O
.	O
</s>
<s>
As	O
of	O
this	O
writing	O
,	O
ITU-R	O
BT.601-6	O
,	O
which	O
is	O
the	O
latest	O
edition	O
of	O
ITU-R	O
BT.601	O
,	O
still	O
implies	O
that	O
the	O
pixel	B-Device
aspect	I-Device
ratios	I-Device
mentioned	O
above	O
are	O
correct	O
.	O
</s>
<s>
As	O
stated	O
above	O
,	O
ITU-R	O
BT.601	O
specified	O
that	O
standard-definition	B-Device
television	I-Device
pictures	O
are	O
made	O
of	O
lines	O
of	O
720	O
non-square	O
pixels	O
,	O
sampled	O
with	O
a	O
precisely	O
specified	O
sampling	O
rate	O
.	O
</s>
<s>
A	O
simple	O
mathematical	O
calculation	O
reveals	O
that	O
a	O
704	O
pixel	B-Algorithm
width	O
would	O
be	O
enough	O
to	O
contain	O
a	O
480i	O
or	O
576i	O
standard	O
4:3	O
picture	O
:	O
</s>
<s>
A	O
4:3	O
480-line	O
picture	O
,	O
digitized	O
with	O
the	O
Rec	O
.	O
</s>
<s>
A	O
4:3	O
576-line	O
picture	O
,	O
digitized	O
with	O
the	O
Rec	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
some	O
analog	O
devices	O
(	O
mostly	O
PAL	B-Language
devices	O
but	O
also	O
some	O
NTSC	O
devices	O
)	O
generated	O
motion	O
pictures	O
that	O
were	O
horizontally	O
(	O
slightly	O
)	O
wider	O
.	O
</s>
<s>
Therefore	O
,	O
to	O
maintain	O
a	O
safe	O
margin	O
of	O
error	O
,	O
ITU-R	O
BT.601	O
required	O
sampling	O
16	O
more	O
non-square	O
pixels	O
per	O
line	B-Application
(	O
8	O
more	O
at	O
each	O
edge	O
)	O
to	O
ensure	O
saving	O
all	O
video	O
data	O
near	O
the	O
margins	O
.	O
</s>
<s>
This	O
requirement	O
,	O
however	O
,	O
had	O
implications	O
for	O
PAL	B-Language
motion	O
pictures	O
.	O
</s>
<s>
PAL	B-Language
pixel	B-Device
aspect	I-Device
ratios	I-Device
for	O
standard	O
(	O
4:3	O
)	O
and	O
anamorphic	O
wide	O
screen	O
(	O
16:9	O
)	O
,	O
respectively	O
59:54	O
and	O
118:81	O
,	O
were	O
awkward	O
for	O
digital	B-Algorithm
image	I-Algorithm
processing	O
,	O
especially	O
for	O
mixing	O
PAL	B-Language
and	O
NTSC	O
video	O
clips	O
.	O
</s>
<s>
Therefore	O
,	O
video	O
editing	O
products	O
chose	O
the	O
almost	O
equivalent	O
values	O
,	O
respectively	O
12:11	O
and	O
16:11	O
,	O
which	O
were	O
more	O
elegant	O
and	O
could	O
create	O
PAL	B-Language
digital	B-Algorithm
images	I-Algorithm
at	O
exactly	O
704	O
pixels	B-Algorithm
wide	O
,	O
as	O
illustrated	O
:	O
</s>
<s>
For	O
PAL	B-Language
4:3	O
:	O
</s>
<s>
For	O
PAL	B-Language
16:9	O
:	O
</s>
<s>
Commonly	O
found	O
on	O
the	O
Internet	O
and	O
in	O
various	O
other	O
published	O
media	O
are	O
numerous	O
sources	O
that	O
introduce	O
different	O
and	O
highly	O
incompatible	O
values	O
as	O
the	O
pixel	B-Device
aspect	I-Device
ratios	I-Device
of	O
various	O
video	O
pictures	O
and	O
video	O
systems	O
.	O
</s>
<s>
To	O
neutrally	O
judge	O
the	O
accuracy	O
and/or	O
feasibility	O
of	O
these	O
sources	O
,	O
please	O
note	O
that	O
as	O
the	O
digital	O
motion	O
picture	O
was	O
invented	O
years	O
after	O
the	O
traditional	O
motion	O
picture	O
,	O
all	O
video	O
pictures	O
targeted	O
for	O
standard	B-Device
definition	I-Device
television	I-Device
and	O
compatible	O
media	O
,	O
digital	O
or	O
otherwise	O
,	O
have	O
(	O
and	O
must	O
have	O
)	O
specifications	O
compatible	O
with	O
standard	B-Device
definition	I-Device
television	I-Device
.	O
</s>
<s>
Therefore	O
,	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
digital	O
video	O
must	O
be	O
calculated	O
from	O
the	O
specification	O
of	O
common	O
traditional	O
equipment	O
rather	O
than	O
the	O
specifications	O
of	O
digital	O
video	O
.	O
</s>
<s>
Otherwise	O
,	O
any	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
that	O
is	O
calculated	O
from	O
a	O
digital	O
video	O
source	O
is	O
only	O
usable	O
in	O
certain	O
cases	O
for	O
the	O
same	O
kind	O
of	O
video	O
sources	O
and	O
cannot	O
be	O
considered/used	O
as	O
a	O
general	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
any	O
standard	B-Device
definition	I-Device
television	I-Device
system	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
common	O
standard	O
television	O
systems	O
cannot	O
be	O
calculated	O
based	O
on	O
edges	O
of	O
pictures	O
.	O
</s>
<s>
Such	O
a	O
calculated	O
aspect	B-Device
ratio	I-Device
value	O
would	O
not	O
be	O
entirely	O
wrong	O
,	O
but	O
also	O
cannot	O
be	O
considered	O
as	O
the	O
general	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
any	O
specific	O
video	O
system	O
.	O
</s>
<s>
In	O
modern	O
digital	B-Algorithm
imaging	I-Algorithm
systems	O
and	O
high-definition	B-Device
televisions	I-Device
,	O
especially	O
those	O
that	O
comply	O
with	O
SMPTE	O
standards	O
and	O
practices	O
,	O
only	O
square	B-Device
pixels	I-Device
are	O
used	O
for	O
broadcast	O
and	O
display	O
.	O
</s>
<s>
Directly	O
mapping	O
an	O
image	O
with	O
a	O
certain	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
on	O
a	O
device	O
whose	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
is	O
different	O
makes	O
the	O
image	O
look	O
unnaturally	O
stretched	O
or	O
squashed	O
in	O
either	O
the	O
horizontal	O
or	O
vertical	O
direction	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
circle	O
generated	O
for	O
a	O
computer	O
display	O
with	O
square	B-Device
pixels	I-Device
looks	O
like	O
a	O
vertical	O
ellipse	O
on	O
a	O
standard-definition	B-Device
NTSC	O
television	O
that	O
uses	O
vertically	O
rectangular	B-Algorithm
pixels	I-Algorithm
.	O
</s>
<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
must	O
be	O
taken	O
into	O
consideration	O
by	O
video	O
editing	O
software	O
products	O
that	O
edit	O
video	O
files	O
with	O
non-square	O
pixels	O
,	O
especially	O
when	O
mixing	O
video	O
clips	O
with	O
different	O
pixel	B-Device
aspect	I-Device
ratios	I-Device
.	O
</s>
<s>
Special	O
effects	O
software	O
products	O
must	O
also	O
take	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
into	O
consideration	O
,	O
since	O
some	O
special	O
effects	O
require	O
calculation	O
of	O
the	O
distances	O
from	O
a	O
certain	O
point	O
so	O
that	O
they	O
look	O
visually	O
correct	O
.	O
</s>
<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
value	O
is	O
used	O
mainly	O
in	O
digital	O
video	O
software	O
,	O
where	O
motion	O
pictures	O
must	O
be	O
converted	O
or	O
reconditioned	O
to	O
use	O
video	O
systems	O
other	O
than	O
the	O
original	O
.	O
</s>
<s>
The	O
video	O
player	O
software	O
may	O
use	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
to	O
properly	O
render	O
digital	O
video	O
on	O
screen	O
.	O
</s>
<s>
Video	O
editing	O
software	O
uses	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
to	O
properly	O
scale	B-Algorithm
and	O
render	O
a	O
video	O
into	O
a	O
new	O
format	O
.	O
</s>
<s>
The	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
support	O
is	O
also	O
required	O
to	O
display	O
,	O
without	O
distortion	O
,	O
legacy	O
digital	B-Algorithm
images	I-Algorithm
from	O
computer	O
standards	O
and	O
video-games	O
what	O
existed	O
in	O
the	O
80s	O
.	O
</s>
<s>
In	O
that	O
generation	O
,	O
square	B-Device
pixels	I-Device
were	O
too	O
expensive	O
to	O
produce	O
,	O
so	O
machines	O
and	O
video	O
cards	O
like	O
the	O
SNES	B-Application
,	O
CGA	B-Device
,	O
EGA	B-Device
,	O
Hercules	B-Device
,	O
C64	O
,	O
MSX	B-Operating_System
,	O
PC-88	B-Device
,	O
X68000	B-Device
etc	O
had	O
non-square	O
pixels	O
.	O
</s>
<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
is	O
often	O
confused	O
with	O
different	O
types	O
of	O
image	O
aspect	B-Device
ratios	I-Device
;	O
the	O
ratio	O
of	O
the	O
image	O
width	O
and	O
height	O
.	O
</s>
<s>
Due	O
to	O
non-squareness	O
of	O
pixels	B-Algorithm
in	O
Standard-definition	B-Device
TV	I-Device
,	O
there	O
are	O
two	O
types	O
of	O
such	O
aspect	B-Device
ratios	I-Device
:	O
storage	O
aspect	B-Device
ratio	I-Device
(	O
SAR	O
)	O
and	O
display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
(	O
abbreviated	O
DAR	O
,	O
also	O
known	O
as	O
image	O
aspect	B-Device
ratio	I-Device
and	O
picture	O
aspect	B-Device
ratio	I-Device
)	O
.	O
</s>
<s>
Also	O
,	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
(	O
PAR	O
)	O
is	O
also	O
known	O
as	O
sample	B-Device
aspect	I-Device
ratio	I-Device
(	O
abbreviated	O
SAR	O
)	O
in	O
some	O
industrial	O
standards	O
(	O
such	O
as	O
H.264	B-Application
)	O
and	O
output	O
of	O
programs	O
(	O
such	O
as	O
ffmpeg	B-Library
)	O
.	O
</s>
<s>
This	O
article	O
uses	O
only	O
the	O
terms	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
,	O
display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
and	O
storage	O
aspect	B-Device
ratio	I-Device
to	O
avoid	O
ambiguity	O
.	O
</s>
<s>
Storage	O
aspect	B-Device
ratio	I-Device
is	O
the	O
ratio	O
of	O
the	O
image	O
width	O
to	O
height	O
in	O
pixels	B-Algorithm
,	O
and	O
can	O
be	O
easily	O
calculated	O
from	O
the	O
video	O
file	O
.	O
</s>
<s>
Display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
is	O
the	O
ratio	O
of	O
image	O
width	O
to	O
height	O
(	O
in	O
a	O
unit	O
of	O
length	O
such	O
as	O
centimeters	O
or	O
inches	O
)	O
when	O
displayed	O
on	O
screen	O
,	O
and	O
is	O
calculated	O
from	O
the	O
combination	O
of	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
and	O
storage	O
aspect	B-Device
ratio	I-Device
.	O
</s>
<s>
Poorly	O
crafted	O
user-interfaces	O
or	O
poorly	O
written	O
documentations	O
can	O
easily	O
cause	O
such	O
confusion	O
:	O
Some	O
video-editing	O
software	O
applications	O
often	O
ask	O
users	O
to	O
specify	O
an	O
"	O
aspect	B-Device
ratio	I-Device
"	O
for	O
their	O
video	O
file	O
,	O
presenting	O
him	O
or	O
her	O
with	O
the	O
choices	O
of	O
"	O
4:3	O
"	O
and	O
"	O
16:9	O
"	O
.	O
</s>
<s>
Sometimes	O
,	O
these	O
choices	O
may	O
be	O
"	O
PAL	B-Language
4:3	O
"	O
,	O
"	O
NTSC	O
4:3	O
"	O
,	O
"	O
PAL	B-Language
16:9	O
"	O
and	O
"	O
NTSC	O
16:9	O
"	O
.	O
</s>
<s>
In	O
such	O
situations	O
,	O
the	O
video	O
editing	O
program	O
is	O
implicitly	O
asking	O
for	O
the	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
the	O
video	O
file	O
by	O
asking	O
for	O
information	O
about	O
the	O
video	O
system	O
from	O
which	O
the	O
video	O
file	O
originated	O
.	O
</s>
<s>
The	O
program	O
then	O
uses	O
a	O
table	O
(	O
similar	O
to	O
the	O
one	O
below	O
)	O
to	O
determine	O
the	O
correct	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
value	O
.	O
</s>
<s>
Generally	O
speaking	O
,	O
to	O
avoid	O
confusion	O
,	O
it	O
can	O
be	O
assumed	O
that	O
video	O
editing	O
products	O
never	O
ask	O
for	O
the	O
storage	O
aspect	B-Device
ratio	I-Device
as	O
they	O
can	O
directly	O
retrieve	O
or	O
calculate	O
it	O
.	O
</s>
<s>
Non-square-pixel	O
–	O
aware	O
applications	O
also	O
need	O
only	O
to	O
ask	O
for	O
either	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
or	O
display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
,	O
from	O
either	O
of	O
which	O
they	O
can	O
calculate	O
the	O
other	O
.	O
</s>
<s>
Pixel	B-Device
aspect	I-Device
ratio	I-Device
values	O
for	O
common	O
standard-definition	B-Device
video	I-Device
formats	O
are	O
listed	O
below	O
.	O
</s>
<s>
Note	O
that	O
for	O
PAL	B-Language
video	B-Application
formats	I-Application
,	O
two	O
different	O
types	O
of	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
values	O
are	O
listed	O
:	O
</s>
<s>
Rec.601	O
,	O
a	O
Rec.601-compliant	O
value	O
,	O
which	O
is	O
considered	O
the	O
real	O
pixel	B-Device
aspect	I-Device
ratio	I-Device
of	O
standard-definition	B-Device
video	I-Device
of	O
that	O
type	O
.	O
</s>
<s>
Note	O
that	O
sources	O
differ	O
on	O
PARs	O
for	O
common	O
formats	O
–	O
for	O
example	O
,	O
576	O
lines	O
(	O
PAL	B-Language
)	O
displayed	O
at	O
4:3	O
(	O
DAR	O
)	O
corresponds	O
to	O
either	O
PAR	O
of	O
12:11	O
(	O
if	O
704×576	O
,	O
SAR	O
=	O
11:9	O
)	O
,	O
or	O
a	O
PAR	O
of	O
16:15	O
(	O
if	O
720×576	O
,	O
SAR	O
=	O
5:4	O
)	O
.	O
</s>
<s>
See	O
references	O
for	O
sources	O
giving	O
both	O
,	O
and	O
SDTV	B-Device
:	O
Resolution	O
for	O
a	O
table	O
of	O
storage	O
,	O
display	O
and	O
pixel	B-Device
aspect	I-Device
ratios	I-Device
.	O
</s>
<s>
Also	O
note	O
that	O
CRT	O
televisions	O
do	O
not	O
have	O
pixels	B-Algorithm
,	O
but	O
scanlines	O
.	O
</s>
<s>
+	O
Non-square	O
aspect	B-Device
ratios	I-Device
of	O
common	O
video	B-Application
formats	I-Application
Video	O
system	O
Picture	O
dimensions( )	O
(	O
decimal	O
)	O
Width	O
(	O
px	O
)	O
Type	O
PAL	B-Language
1.0	O
769	O
,	O
385	O
Rec.601	O
1	O
.	O
</s>
