<s>
Generation	B-General_Concept
loss	I-General_Concept
is	O
the	O
loss	O
of	O
quality	O
between	O
subsequent	O
copies	O
or	O
transcodes	B-Algorithm
of	O
data	O
.	O
</s>
<s>
Anything	O
that	O
reduces	O
the	O
quality	O
of	O
the	O
representation	O
when	O
copying	O
,	O
and	O
would	O
cause	O
further	O
reduction	O
in	O
quality	O
on	O
making	O
a	O
copy	O
of	O
the	O
copy	O
,	O
can	O
be	O
considered	O
a	O
form	O
of	O
generation	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
File	O
size	O
increases	O
are	O
a	O
common	O
result	O
of	O
generation	B-General_Concept
loss	I-General_Concept
,	O
as	O
the	O
introduction	O
of	O
artifacts	B-Algorithm
may	O
actually	O
increase	O
the	O
entropy	O
of	O
the	O
data	O
through	O
each	O
generation	O
.	O
</s>
<s>
In	O
analog	O
systems	O
(	O
including	O
systems	O
that	O
use	O
digital	O
recording	O
but	O
make	O
the	O
copy	O
over	O
an	O
analog	O
connection	O
)	O
,	O
generation	B-General_Concept
loss	I-General_Concept
is	O
mostly	O
due	O
to	O
noise	O
and	O
bandwidth	B-Algorithm
issues	O
in	O
cables	O
,	O
amplifiers	O
,	O
mixers	O
,	O
recording	O
equipment	O
and	O
anything	O
else	O
between	O
the	O
source	O
and	O
the	O
destination	O
.	O
</s>
<s>
Generation	B-General_Concept
loss	I-General_Concept
was	O
a	O
major	O
consideration	O
in	O
complex	O
analog	O
audio	O
and	O
video	O
editing	O
,	O
where	O
multi-layered	O
edits	O
were	O
often	O
created	O
by	O
making	O
intermediate	O
mixes	O
which	O
were	O
then	O
"	O
bounced	O
down	O
"	O
back	O
onto	O
tape	O
.	O
</s>
<s>
Careful	O
planning	O
was	O
required	O
to	O
minimize	O
generation	B-General_Concept
loss	I-General_Concept
,	O
and	O
the	O
resulting	O
noise	O
and	O
poor	O
frequency	O
response	O
.	O
</s>
<s>
The	O
introduction	O
of	O
professional	O
analog	O
noise	O
reduction	O
systems	O
such	O
as	O
Dolby	O
A	O
helped	O
reduce	O
the	O
amount	O
of	O
audible	O
generation	B-General_Concept
loss	I-General_Concept
,	O
but	O
were	O
eventually	O
superseded	O
by	O
digital	O
systems	O
which	O
vastly	O
reduced	O
generation	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
According	O
to	O
ATIS	O
,	O
"	O
Generation	B-General_Concept
loss	I-General_Concept
is	O
limited	O
to	O
analog	O
recording	O
because	O
digital	O
recording	O
and	O
reproduction	O
may	O
be	O
performed	O
in	O
a	O
manner	O
that	O
is	O
essentially	O
free	O
from	O
generation	O
loss.	O
"	O
</s>
<s>
Used	O
correctly	O
,	O
digital	O
technology	O
can	O
eliminate	O
generation	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
This	O
implies	O
the	O
exclusive	O
use	O
of	O
lossless	B-Algorithm
compression	I-Algorithm
codecs	O
or	O
uncompressed	B-General_Concept
data	O
from	O
recording	O
or	O
creation	O
until	O
the	O
final	O
lossy	B-Algorithm
encode	O
for	O
distribution	O
through	O
internet	O
streaming	O
or	O
optical	O
discs	O
.	O
</s>
<s>
Generation	B-General_Concept
loss	I-General_Concept
can	O
still	O
occur	O
when	O
using	O
lossy	B-Algorithm
video	O
or	O
audio	O
compression	O
codecs	O
as	O
these	O
introduce	O
artifacts	B-Algorithm
into	O
the	O
source	O
material	O
with	O
each	O
encode	O
or	O
reencode	O
.	O
</s>
<s>
Lossy	B-Algorithm
compression	I-Algorithm
codecs	O
such	O
as	O
Apple	B-Algorithm
ProRes	I-Algorithm
,	O
Advanced	B-Application
Video	I-Application
Coding	I-Application
and	O
mp3	B-Application
are	O
very	O
widely	O
used	O
as	O
they	O
allow	O
for	O
dramatic	O
reductions	O
on	O
file	O
size	O
while	O
being	O
indistinguishable	O
from	O
the	O
uncompressed	B-General_Concept
or	O
losslessly	B-Algorithm
compressed	O
original	O
for	O
viewing	O
purposes	O
.	O
</s>
<s>
The	O
only	O
way	O
to	O
avoid	O
generation	B-General_Concept
loss	I-General_Concept
is	O
by	O
using	O
uncompressed	B-General_Concept
or	O
losslessly	B-Algorithm
compressed	O
files	O
;	O
which	O
may	O
be	O
expensive	O
from	O
a	O
storage	O
standpoint	O
as	O
they	O
require	O
larger	O
amounts	O
of	O
storage	O
space	O
in	O
flash	O
memory	O
or	O
hard	O
drives	O
per	O
second	O
of	O
runtime	O
.	O
</s>
<s>
Uncompressed	B-General_Concept
video	O
requires	O
a	O
high	O
data	O
rate	O
;	O
for	O
example	O
,	O
a	O
1080p	O
video	O
at	O
30	O
frames	O
per	O
second	O
can	O
require	O
up	O
to	O
370	O
megabytes	O
per	O
second	O
.	O
</s>
<s>
Lossy	B-Algorithm
codecs	O
make	O
Blu-rays	O
and	O
streaming	O
video	O
over	O
the	O
internet	O
feasible	O
since	O
neither	O
can	O
deliver	O
the	O
amounts	O
of	O
data	O
needed	O
for	O
uncompressed	B-General_Concept
or	O
losslessly	B-Algorithm
compressed	O
video	O
at	O
acceptable	O
frame	O
rates	O
and	O
resolutions	O
.	O
</s>
<s>
Images	O
can	O
suffer	O
from	O
generation	B-General_Concept
loss	I-General_Concept
in	O
the	O
same	O
way	O
video	O
and	O
audio	O
can	O
.	O
</s>
<s>
Processing	O
a	O
lossily	B-General_Concept
compressed	I-General_Concept
file	O
rather	O
than	O
an	O
original	O
usually	O
results	O
in	O
more	O
loss	O
of	O
quality	O
than	O
generating	O
the	O
same	O
output	O
from	O
an	O
uncompressed	B-General_Concept
original	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
low-resolution	O
digital	O
image	O
for	O
a	O
web	O
page	O
is	O
better	O
if	O
generated	O
from	O
an	O
uncompressed	B-General_Concept
raw	B-Application
image	I-Application
than	O
from	O
an	O
already-compressed	O
JPEG	O
file	O
of	O
higher	O
quality	O
.	O
</s>
<s>
In	O
digital	O
systems	O
,	O
several	O
techniques	O
,	O
used	O
because	O
of	O
other	O
advantages	O
,	O
may	O
introduce	O
generation	B-General_Concept
loss	I-General_Concept
and	O
must	O
be	O
used	O
with	O
caution	O
.	O
</s>
<s>
However	O
,	O
copying	O
a	O
digital	O
file	O
itself	O
incurs	O
no	O
generation	B-General_Concept
loss	I-General_Concept
—	O
the	O
copied	O
file	O
is	O
identical	O
to	O
the	O
original	O
,	O
provided	O
a	O
perfect	O
copying	O
channel	O
is	O
used	O
.	O
</s>
<s>
Some	O
digital	B-General_Concept
transforms	I-General_Concept
are	O
reversible	O
,	O
while	O
some	O
are	O
not	O
.	O
</s>
<s>
Lossless	B-Algorithm
compression	I-Algorithm
is	O
,	O
by	O
definition	O
,	O
fully	O
reversible	O
,	O
while	O
lossy	B-Algorithm
compression	I-Algorithm
throws	O
away	O
some	O
data	O
which	O
cannot	O
be	O
restored	O
.	O
</s>
<s>
Similarly	O
,	O
many	O
DSP	B-General_Concept
processes	O
are	O
not	O
reversible	O
.	O
</s>
<s>
Thus	O
careful	O
planning	O
of	O
an	O
audio	O
or	O
video	O
signal	O
chain	O
from	O
beginning	O
to	O
end	O
and	O
rearranging	O
to	O
minimize	O
multiple	O
conversions	O
is	O
important	O
to	O
avoid	O
generation	B-General_Concept
loss	I-General_Concept
when	O
using	O
lossy	B-Algorithm
compression	I-Algorithm
codecs	O
.	O
</s>
<s>
Often	O
,	O
arbitrary	O
choices	O
of	O
numbers	O
of	O
pixels	O
and	O
sampling	O
rates	O
for	O
source	O
,	O
destination	O
,	O
and	O
intermediates	O
can	O
seriously	O
degrade	O
digital	O
signals	O
in	O
spite	O
of	O
the	O
potential	O
of	O
digital	O
technology	O
for	O
eliminating	O
generation	B-General_Concept
loss	I-General_Concept
completely	O
.	O
</s>
<s>
Similarly	O
,	O
when	O
using	O
lossy	B-Algorithm
compression	I-Algorithm
,	O
it	O
will	O
ideally	O
only	O
be	O
done	O
once	O
,	O
at	O
the	O
end	O
of	O
the	O
workflow	O
involving	O
the	O
file	O
,	O
after	O
all	O
required	O
changes	O
have	O
been	O
made	O
.	O
</s>
<s>
Converting	O
between	O
lossy	B-Algorithm
formats	O
–	O
be	O
it	O
decoding	O
and	O
re-encoding	O
to	O
the	O
same	O
format	O
,	O
between	O
different	O
formats	O
,	O
or	O
between	O
different	O
bitrates	O
or	O
parameters	O
of	O
the	O
same	O
format	O
–	O
causes	O
generation	B-General_Concept
loss	I-General_Concept
.	O
</s>
<s>
Repeated	O
applications	O
of	O
lossy	B-Algorithm
compression	I-Algorithm
and	O
decompression	O
can	O
cause	O
generation	B-General_Concept
loss	I-General_Concept
,	O
particularly	O
if	O
the	O
parameters	O
used	O
are	O
not	O
consistent	O
across	O
generations	O
.	O
</s>
<s>
Ideally	O
an	O
algorithm	O
will	O
be	O
both	O
idempotent	O
,	O
meaning	O
that	O
if	O
the	O
signal	O
is	O
decoded	O
and	O
then	O
re-encoded	O
with	O
identical	O
settings	O
,	O
there	O
is	O
no	O
loss	O
,	O
and	O
scalable	O
,	O
meaning	O
that	O
if	O
it	O
is	O
re-encoded	O
with	O
lower	O
quality	O
settings	O
,	O
the	O
result	O
will	O
be	O
the	O
same	O
as	O
if	O
it	O
had	O
been	O
encoded	O
from	O
the	O
original	O
signal	O
–	O
see	O
Scalable	B-Application
Video	I-Application
Coding	I-Application
.	O
</s>
<s>
More	O
generally	O
,	O
transcoding	B-Algorithm
between	O
different	O
parameters	O
of	O
a	O
particular	O
encoding	O
will	O
ideally	O
yield	O
the	O
greatest	O
common	O
shared	O
quality	O
–	O
for	O
instance	O
,	O
converting	O
from	O
an	O
image	O
with	O
4	O
bits	O
of	O
red	O
and	O
8	O
bits	O
of	O
green	O
to	O
one	O
with	O
8	O
bits	O
of	O
red	O
and	O
4	O
bits	O
of	O
green	O
would	O
ideally	O
yield	O
simply	O
an	O
image	O
with	O
4	O
bits	O
of	O
red	O
color	O
depth	O
and	O
4	O
bits	O
of	O
green	O
color	O
depth	O
without	O
further	O
degradation	O
.	O
</s>
<s>
Some	O
lossy	B-Algorithm
compression	I-Algorithm
algorithms	O
are	O
much	O
worse	O
than	O
others	O
in	O
this	O
regard	O
,	O
being	O
neither	O
idempotent	O
nor	O
scalable	O
,	O
and	O
introducing	O
further	O
degradation	O
if	O
parameters	O
are	O
changed	O
.	O
</s>
<s>
For	O
example	O
,	O
with	O
JPEG	O
,	O
changing	O
the	O
quality	O
setting	O
will	O
cause	O
different	O
quantization	B-Algorithm
constants	O
to	O
be	O
used	O
,	O
causing	O
additional	O
loss	O
.	O
</s>
<s>
Digital	O
resampling	B-Algorithm
such	O
as	O
image	B-Algorithm
scaling	I-Algorithm
,	O
and	O
other	O
DSP	B-General_Concept
techniques	O
can	O
also	O
introduce	O
artifacts	B-Algorithm
or	O
degrade	O
signal-to-noise	O
ratio	O
(	O
S/N	O
ratio	O
)	O
each	O
time	O
they	O
are	O
used	O
,	O
even	O
if	O
the	O
underlying	O
storage	O
is	O
lossless	B-Algorithm
.	O
</s>
<s>
Resampling	B-Algorithm
causes	O
aliasing	B-Error_Name
,	O
both	O
blurring	O
low-frequency	O
components	O
and	O
adding	O
high-frequency	O
noise	O
,	O
causing	O
jaggies	B-Algorithm
,	O
while	O
rounding	O
off	O
computations	O
to	O
fit	O
in	O
finite	O
precision	O
introduces	O
quantization	B-Algorithm
,	O
causing	O
banding	B-Algorithm
;	O
if	O
fixed	O
by	O
dither	O
,	O
this	O
instead	O
becomes	O
noise	O
.	O
</s>
<s>
In	O
both	O
cases	O
,	O
these	O
at	O
best	O
degrade	O
the	O
signal	O
's	O
S/N	O
ratio	O
,	O
and	O
may	O
cause	O
artifacts	B-Algorithm
.	O
</s>
<s>
Quantization	B-Algorithm
can	O
be	O
reduced	O
by	O
using	O
high	O
precision	O
while	O
editing	O
(	O
notably	O
floating	O
point	O
numbers	O
)	O
,	O
only	O
reducing	O
back	O
to	O
fixed	O
precision	O
at	O
the	O
end	O
.	O
</s>
<s>
It	O
has	O
been	O
documented	O
that	O
successive	O
repostings	O
on	O
Instagram	B-Application
results	O
in	O
noticeable	O
changes	O
.	O
</s>
<s>
Likewise	O
,	O
repeated	O
postings	O
on	O
YouTube	B-General_Concept
degraded	O
the	O
work	O
.	O
</s>
<s>
This	O
is	O
because	O
both	O
services	O
use	O
lossy	B-Algorithm
codecs	O
on	O
all	O
data	O
that	O
is	O
uploaded	O
to	O
them	O
,	O
even	O
if	O
the	O
data	O
being	O
uploaded	O
is	O
a	O
duplicate	O
of	O
data	O
already	O
hosted	O
on	O
the	O
service	O
,	O
while	O
VHS	O
is	O
an	O
analog	O
medium	O
,	O
where	O
effects	O
such	O
as	O
noise	O
from	O
interference	O
can	O
have	O
a	O
much	O
more	O
noticeable	O
impact	O
on	O
recordings	O
.	O
</s>
