<s>
QuickTime	B-Algorithm
Animation	I-Algorithm
format	O
(	O
also	O
known	O
as	O
QuickTime	B-Application
RLE	O
)	O
is	O
a	O
video	B-Algorithm
compression	I-Algorithm
format	I-Algorithm
and	O
codec	B-Application
created	O
by	O
Apple	O
Computer	O
to	O
enable	O
playback	O
of	O
RGB	O
video	O
in	O
real	B-General_Concept
time	I-General_Concept
without	O
expensive	O
hardware	O
.	O
</s>
<s>
It	O
is	O
generally	O
found	O
in	O
the	O
QuickTime	B-Application
container	O
with	O
the	O
FourCC	B-Application
'	O
rle	O
'	O
.	O
</s>
<s>
It	O
can	O
perform	O
either	O
lossless	B-Algorithm
or	O
lossy	B-Algorithm
compression	I-Algorithm
and	O
is	O
one	O
of	O
the	O
few	O
video	B-Application
codecs	I-Application
that	O
supports	O
an	O
alpha	B-Algorithm
channel	I-Algorithm
.	O
</s>
<s>
Supported	O
color	O
depths	O
are	O
1-bit	O
(	O
monochrome	O
)	O
,	O
15-bit	O
RGB	O
,	O
24-bit	O
RGB	O
,	O
32-bit	O
ARGB	O
,	O
as	O
well	O
as	O
palettized	B-Data_Structure
RGB	O
.	O
</s>
<s>
As	O
a	O
result	O
of	O
reverse-engineering	O
of	O
the	O
format	O
,	O
a	O
decoder	O
is	O
implemented	O
in	O
XAnim	O
as	O
well	O
as	O
an	O
encoder	O
and	O
decoder	O
in	O
libavcodec	B-Language
.	O
</s>
<s>
QuickTime	B-Algorithm
Animation	I-Algorithm
uses	O
run-length	B-Algorithm
encoding	I-Algorithm
and	O
conditional	O
replenishment	O
for	O
compression	O
.	O
</s>
<s>
For	O
each	O
run	O
,	O
one	O
of	O
three	O
coding	O
modes	O
is	O
used	O
:	O
same	O
color	O
,	O
skip	O
,	O
or	O
PCM	B-Algorithm
.	O
</s>
<s>
In	O
same	O
color	O
mode	O
,	O
a	O
run	O
of	O
pixels	O
is	O
represented	O
by	O
a	O
single	O
color	O
in	O
a	O
run-length	B-Algorithm
encoding	I-Algorithm
fashion	O
.	O
</s>
<s>
If	O
pixels	O
with	O
different	O
colors	O
are	O
joined	O
into	O
a	O
run	O
(	O
of	O
a	O
single	O
color	O
)	O
by	O
the	O
encoder	O
,	O
the	O
coding	O
process	O
is	O
lossy	B-Algorithm
,	O
otherwise	O
it	O
is	O
lossless	B-Algorithm
.	O
</s>
<s>
The	O
lossless	B-Algorithm
mode	O
is	O
used	O
at	O
the	O
100%	O
quality	O
level	O
.	O
</s>
<s>
In	O
PCM	B-Algorithm
mode	O
,	O
the	O
color	O
of	O
each	O
pixel	O
is	O
written	O
to	O
the	O
bitstream	O
,	O
without	O
any	O
compression	O
.	O
</s>
<s>
Run-length	B-Algorithm
encoding	I-Algorithm
works	O
well	O
on	O
content	O
with	O
large	O
areas	O
of	O
constant	O
color	O
.	O
</s>
<s>
QuickTime	B-Algorithm
Animation	I-Algorithm
works	O
well	O
on	O
content	O
with	O
both	O
these	O
properties	O
,	O
such	O
as	O
traditional	O
2-D	O
animation	O
and	O
screencast	O
content	O
.	O
</s>
<s>
For	O
natural	O
video	O
and	O
complex	O
3D	O
rendered	O
scenes	O
,	O
in	O
which	O
runs	O
of	O
constant	O
color	O
rarely	O
occur	O
,	O
only	O
low	O
compression	O
ratios	O
can	O
be	O
achieved	O
in	O
lossless	B-Algorithm
mode	O
,	O
and	O
the	O
merging	O
of	O
runs	O
becomes	O
visible	O
as	O
noise	O
in	O
lossy	B-Algorithm
mode	O
.	O
</s>
