<s>
Transcoding	B-Algorithm
is	O
the	O
direct	O
digital-to-digital	O
conversion	O
of	O
one	O
encoding	B-General_Concept
to	O
another	O
,	O
such	O
as	O
for	O
video	O
data	O
files	O
,	O
audio	O
files	O
(	O
e.g.	O
,	O
MP3	B-Application
,	O
WAV	O
)	O
,	O
or	O
character	B-General_Concept
encoding	I-General_Concept
(	O
e.g.	O
,	O
UTF-8	O
,	O
ISO/IEC	O
8859	O
)	O
.	O
</s>
<s>
This	O
is	O
usually	O
done	O
in	O
cases	O
where	O
a	O
target	O
device	O
(	O
or	O
workflow	B-Operating_System
)	O
does	O
not	O
support	O
the	O
format	O
or	O
has	O
limited	O
storage	B-General_Concept
capacity	I-General_Concept
that	O
mandates	O
a	O
reduced	O
file	B-General_Concept
size	I-General_Concept
,	O
or	O
to	O
convert	O
incompatible	O
or	O
obsolete	O
data	O
to	O
a	O
better-supported	O
or	O
modern	O
format	O
.	O
</s>
<s>
In	O
the	O
analog	O
video	O
world	O
,	O
transcoding	B-Algorithm
can	O
be	O
performed	O
just	O
while	O
files	O
are	O
being	O
searched	O
,	O
as	O
well	O
as	O
for	O
presentation	O
.	O
</s>
<s>
However	O
,	O
transcoding	B-Algorithm
into	O
a	O
JPEG2000	O
lossless	O
format	O
has	O
better	O
compression	O
performance	O
than	O
other	O
lossless	O
coding	O
technologies	O
,	O
and	O
in	O
many	O
cases	O
,	O
JPEG2000	O
can	O
compress	O
images	O
to	O
half-size	O
.	O
</s>
<s>
Transcoding	B-Algorithm
is	O
commonly	O
a	O
lossy	B-Algorithm
process	I-Algorithm
,	O
introducing	O
generation	B-General_Concept
loss	I-General_Concept
;	O
however	O
,	O
transcoding	B-Algorithm
can	O
be	O
lossless	O
if	O
the	O
output	O
is	O
either	O
losslessly	O
compressed	O
or	O
uncompressed	B-General_Concept
.	O
</s>
<s>
The	O
process	O
of	O
transcoding	B-Algorithm
into	O
a	O
lossy	B-Algorithm
format	O
introduces	O
varying	O
degrees	O
of	O
generation	B-General_Concept
loss	I-General_Concept
,	O
while	O
the	O
transcoding	B-Algorithm
from	O
lossy	B-Algorithm
to	O
lossless	O
or	O
uncompressed	B-General_Concept
is	O
technically	O
a	O
lossless	O
conversion	O
because	O
no	O
information	O
is	O
lost	O
;	O
however	O
,	O
when	O
the	O
conversion	O
is	O
irreversible	O
,	O
it	O
is	O
then	O
more	O
correctly	O
known	O
as	O
destructive	O
.	O
</s>
<s>
Transcoding	B-Algorithm
is	O
a	O
two-step	O
process	O
in	O
which	O
the	O
original	O
data	O
is	O
decoded	O
to	O
an	O
intermediate	O
uncompressed	B-General_Concept
format	O
(	O
e.g.	O
,	O
PCM	B-Algorithm
for	O
audio	O
;	O
YUV	O
for	O
video	O
)	O
,	O
which	O
is	O
then	O
encoded	O
into	O
the	O
target	O
format	O
.	O
</s>
<s>
If	O
one	O
wishes	O
to	O
edit	O
data	O
in	O
a	O
compressed	O
format	O
(	O
for	O
instance	O
,	O
perform	O
image	B-Application
editing	I-Application
on	O
a	O
JPEG	O
image	O
)	O
,	O
one	O
will	O
generally	O
decode	O
it	O
,	O
edit	O
it	O
,	O
then	O
re-encode	O
it	O
.	O
</s>
<s>
This	O
re-encoding	O
causes	O
digital	O
generation	B-General_Concept
loss	I-General_Concept
;	O
thus	O
if	O
one	O
wishes	O
to	O
edit	O
a	O
file	O
repeatedly	O
,	O
one	O
should	O
only	O
decode	O
it	O
once	O
,	O
and	O
make	O
all	O
edits	O
on	O
that	O
copy	O
,	O
rather	O
than	O
repeatedly	O
re-encoding	O
it	O
.	O
</s>
<s>
Similarly	O
,	O
if	O
encoding	B-General_Concept
to	O
a	O
lossy	B-Algorithm
format	O
is	O
required	O
,	O
it	O
should	O
be	O
deferred	O
until	O
the	O
data	O
is	O
finalised	O
,	O
e.g.	O
</s>
<s>
Transrating	B-General_Concept
is	O
a	O
process	O
similar	O
to	O
transcoding	B-Algorithm
in	O
which	O
files	O
are	O
coded	O
to	O
a	O
lower	O
bitrate	O
without	O
changing	O
video	O
formats	O
;	O
this	O
can	O
include	O
sample	O
rate	O
conversion	O
,	O
but	O
may	O
use	O
an	O
identical	O
sampling	O
rate	O
with	O
higher	O
compression	O
.	O
</s>
<s>
On	O
a	O
powerful	O
enough	O
device	O
,	O
image	B-Algorithm
scaling	I-Algorithm
can	O
be	O
done	O
on	O
playback	O
,	O
but	O
it	O
can	O
also	O
be	O
done	O
by	O
re-encoding	O
,	O
particularly	O
as	O
part	O
of	O
transrating	B-General_Concept
(	O
such	O
as	O
a	O
downsampled	B-Algorithm
image	O
requiring	O
a	O
lower	O
bitrate	O
)	O
.	O
</s>
<s>
One	O
can	O
also	O
use	O
formats	O
with	O
bitrate	B-General_Concept
peeling	I-General_Concept
,	O
that	O
allow	O
one	O
to	O
easily	O
lower	O
the	O
bitrate	O
without	O
re-encoding	O
,	O
but	O
quality	O
is	O
often	O
lower	O
than	O
a	O
re-encode	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
Vorbis	B-Algorithm
bitrate	B-General_Concept
peeling	I-General_Concept
as	O
of	O
2008	O
,	O
the	O
quality	O
is	O
inferior	O
to	O
re-encoding	O
.	O
</s>
<s>
The	O
key	O
drawback	O
of	O
transcoding	B-Algorithm
in	O
lossy	B-Algorithm
formats	O
is	O
decreased	O
quality	O
.	O
</s>
<s>
Compression	B-Algorithm
artifacts	I-Algorithm
are	O
cumulative	O
,	O
so	O
transcoding	B-Algorithm
causes	O
a	O
progressive	O
loss	O
of	O
quality	O
with	O
each	O
successive	O
generation	O
,	O
known	O
as	O
digital	O
generation	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
transcoding	B-Algorithm
(	O
in	O
lossy	B-Algorithm
formats	O
)	O
is	O
generally	O
discouraged	O
unless	O
unavoidable	O
.	O
</s>
<s>
For	O
users	O
wanting	O
to	O
be	O
able	O
to	O
re-encode	O
audio	O
into	O
any	O
format	O
,	O
and	O
for	O
digital	B-Application
audio	I-Application
editing	I-Application
,	O
it	O
is	O
best	O
to	O
retain	O
a	O
master	O
copy	O
in	O
a	O
lossless	O
format	O
(	O
such	O
as	O
FLAC	B-Application
,	O
ALAC	B-Algorithm
,	O
TTA	B-Algorithm
,	O
WavPack	B-Application
,	O
and	O
others	O
)	O
that	O
take	O
around	O
half	O
the	O
storage	O
space	O
needed	O
when	O
compared	O
to	O
original	O
uncompressed	B-General_Concept
PCM	B-Algorithm
formats	O
(	O
such	O
as	O
WAV	O
,	O
and	O
AIFF	O
)	O
,	O
as	O
lossless	O
formats	O
usually	O
have	O
the	O
added	O
benefit	O
of	O
having	O
meta	O
data	O
options	O
,	O
which	O
are	O
either	O
completely	O
missing	O
or	O
very	O
limited	O
in	O
PCM	B-Algorithm
formats	O
.	O
</s>
<s>
These	O
lossless	O
formats	O
can	O
be	O
transcoded	O
to	O
PCM	B-Algorithm
formats	O
or	O
transcoded	O
directly	O
from	O
one	O
lossless	O
format	O
to	O
another	O
lossless	O
format	O
,	O
without	O
any	O
loss	O
in	O
quality	O
.	O
</s>
<s>
They	O
can	O
be	O
transcoded	O
into	O
a	O
lossy	B-Algorithm
format	O
,	O
but	O
these	O
copies	O
will	O
then	O
not	O
be	O
able	O
to	O
be	O
transcoded	O
into	O
another	O
format	O
of	O
any	O
kind	O
(	O
PCM	B-Algorithm
,	O
lossless	O
,	O
or	O
lossy	B-Algorithm
)	O
without	O
a	O
subsequent	O
loss	O
of	O
quality	O
.	O
</s>
<s>
For	O
image	B-Application
editing	I-Application
users	O
are	O
advised	O
to	O
capture	O
or	O
save	O
images	O
in	O
a	O
raw	B-Application
or	O
uncompressed	B-General_Concept
format	O
,	O
and	O
then	O
edit	O
a	O
copy	O
of	O
that	O
master	O
version	O
,	O
only	O
converting	O
to	O
lossy	B-Algorithm
formats	O
if	O
smaller	O
file	O
sized	O
images	O
are	O
needed	O
for	O
final	O
distribution	O
.	O
</s>
<s>
As	O
with	O
audio	O
,	O
transcoding	B-Algorithm
from	O
lossy	B-Algorithm
format	O
to	O
another	O
format	O
of	O
any	O
type	O
will	O
result	O
in	O
a	O
loss	O
of	O
quality	O
.	O
</s>
<s>
For	O
video	O
editing	O
,	O
(	O
for	O
video	O
converting	O
)	O
,	O
images	O
are	O
normally	O
compressed	O
directly	O
during	O
the	O
recording	O
process	O
due	O
to	O
the	O
huge	O
file	B-General_Concept
sizes	I-General_Concept
that	O
would	O
be	O
created	O
if	O
they	O
were	O
not	O
,	O
and	O
because	O
the	O
huge	O
storage	O
demands	O
being	O
too	O
cumbersome	O
for	O
the	O
user	O
otherwise	O
.	O
</s>
<s>
Effectively	O
this	O
means	O
that	O
any	O
transcoding	B-Algorithm
will	O
involve	O
some	O
cumulative	O
image	O
loss	O
,	O
and	O
hence	O
the	O
most	O
practical	O
solution	O
insofar	O
as	O
minimizing	O
loss	O
of	O
quality	O
is	O
for	O
the	O
original	O
recording	O
to	O
be	O
deemed	O
the	O
master	O
copy	O
,	O
and	O
for	O
desired	O
subsequent	O
transcoded	O
versions	O
,	O
which	O
will	O
often	O
be	O
in	O
a	O
different	O
format	O
and	O
smaller	O
file	B-General_Concept
size	I-General_Concept
,	O
to	O
be	O
transcoded	O
only	O
from	O
that	O
master	O
copy	O
.	O
</s>
<s>
Although	O
transcoding	B-Algorithm
can	O
be	O
found	O
in	O
many	O
areas	O
of	O
content	O
adaptation	O
,	O
it	O
is	O
commonly	O
used	O
in	O
the	O
area	O
of	O
mobile	O
phone	O
content	O
adaptation	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
transcoding	B-Algorithm
is	O
a	O
must	O
,	O
due	O
to	O
the	O
diversity	O
of	O
mobile	B-Application
devices	I-Application
and	O
their	O
capabilities	O
.	O
</s>
<s>
Transcoding	B-Algorithm
video	O
from	O
most	O
consumer	O
digital	B-Device
cameras	I-Device
can	O
reduce	O
the	O
file	B-General_Concept
size	I-General_Concept
significantly	O
while	O
keeping	O
the	O
quality	O
about	O
the	O
same	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
popular	O
technologies	O
in	O
which	O
transcoding	B-Algorithm
is	O
used	O
is	O
the	O
Multimedia	O
Messaging	O
Service	O
(	O
MMS	O
)	O
,	O
which	O
is	O
the	O
technology	O
used	O
to	O
send	O
or	O
receive	O
messages	O
with	O
media	O
(	O
image	O
,	O
sound	O
,	O
text	O
and	O
video	O
)	O
between	O
mobile	O
phones	O
.	O
</s>
<s>
For	O
example	O
,	O
when	O
a	O
camera	O
phone	O
is	O
used	O
to	O
take	O
a	O
digital	O
picture	O
,	O
a	O
high-quality	O
image	O
of	O
usually	O
at	O
least	O
640x480	O
pixels	B-Algorithm
is	O
created	O
.	O
</s>
<s>
This	O
size	O
and	O
color	O
reduction	O
improves	O
the	O
user	O
experience	O
on	O
the	O
target	O
device	O
,	O
and	O
is	O
sometimes	O
the	O
only	O
way	O
for	O
content	O
to	O
be	O
sent	O
between	O
different	O
mobile	B-Application
devices	I-Application
.	O
</s>
<s>
Transcoding	B-Algorithm
is	O
extensively	O
used	O
by	O
home	O
theatre	O
PC	O
software	O
to	O
reduce	O
the	O
usage	O
of	O
disk	B-General_Concept
space	I-General_Concept
by	O
video	O
files	O
.	O
</s>
<s>
The	O
most	O
common	O
operation	O
in	O
this	O
application	O
is	O
the	O
transcoding	B-Algorithm
of	O
MPEG-2	B-Algorithm
files	O
to	O
the	O
MPEG-4	B-Algorithm
or	O
H.264	B-Application
format	O
.	O
</s>
<s>
Real-time	O
transcoding	B-Algorithm
in	O
a	O
many-to-many	O
way	O
(	O
any	O
input	O
format	O
to	O
any	O
output	O
format	O
)	O
is	O
becoming	O
a	O
necessity	O
to	O
provide	O
true	O
search	O
capability	O
for	O
any	O
multimedia	O
content	O
on	O
any	O
mobile	B-Application
device	I-Application
,	O
with	O
over	O
500	O
million	O
videos	O
on	O
the	O
web	O
and	O
a	O
plethora	O
of	O
mobile	B-Application
devices	I-Application
.	O
</s>
<s>
Before	O
the	O
advent	O
of	O
semiconductors	O
and	O
integrated	O
circuits	O
,	O
realtime	O
resolution	O
and	O
frame	O
rate	O
transcoding	B-Algorithm
between	O
different	O
analog	O
video	O
standards	O
was	O
achieved	O
by	O
a	O
CRT/camera	O
tube	O
combination	O
.	O
</s>
<s>
The	O
CRT	B-Device
part	O
does	O
not	O
write	O
onto	O
a	O
phosphor	O
,	O
but	O
onto	O
a	O
thin	O
,	O
dielectric	O
target	O
;	O
the	O
camera	O
part	O
reads	O
the	O
deposited	O
charge	O
pattern	O
at	O
a	O
different	O
scan	O
rate	O
from	O
the	O
back	O
side	O
of	O
this	O
target	O
.	O
</s>
