56
Using 8-bit Versus 10-bit Video
While both 8- and 10-bit unco
m
pressed video are capable of providing excellent quality
broadcast video, 10-bit represents a significantly higher quality and is preferable in
m
any
situations.
Because 10-bit video has four ti
m
es the nu
m
erical precision when co
m
pared to 8-bit, it has a
signal-to-noise ratio 12 db higher than 8-bit video.
Visually, in 8-bit video co
m
pared to 10-bit video, you will notice a substantial difference. In 8-
bit video there will be “contour lines” or “striations” visible, particularly noticeable in scenes
having soft gradients like a ra
m
p or sunset. For exa
m
ple, if a sky region is
m
ostly the sa
m
e
color but varies by only a few digital nu
m
bers fro
m
one side of the picture to another, you
m
ay see contour lines where the signal passes fro
m
one digital value to the next higher value.
Since each nu
m
erical value in a 10-bit syste
m
is only one fourth as large as an 8-bit syste
m
's,
these contours beco
m
e invisible and the sky varies s
m
oothly.
10-bit video is often used when the source and output video (or “
m
aster”) is also 10-bit. Even
if the input and/or output video is 8-bit, a 10-bit “project” will still
m
aintain a higher quality
when there is a significant a
m
ount of effects rendering involved.
Industry standard professional
m
astering for
m
ats—Sony Digital Betaca
m
for Standard
Definition and Panasonic D5 for High Definition—are both true 10-bit for
m
ats.
USO
RESTRITO
