<s>
ITU-R	B-Device
Recommendation	I-Device
BT.656	I-Device
,	O
sometimes	O
also	O
called	O
ITU656	B-Device
,	O
describes	O
a	O
simple	O
digital	O
video	O
protocol	O
for	O
streaming	O
uncompressed	O
PAL	B-Language
or	O
NTSC	O
standard-definition	B-Device
television	I-Device
(	O
625	O
or	O
525	O
lines	O
)	O
signals	O
.	O
</s>
<s>
The	O
protocol	O
builds	O
upon	O
the	O
4:2:2	O
digital	O
video	O
encoding	O
parameters	O
defined	O
in	O
ITU-R	O
Recommendation	O
BT.601	O
,	O
which	O
provides	O
interlaced	O
video	O
data	O
,	O
streaming	O
each	O
field	O
separately	O
,	O
and	O
uses	O
the	O
YCbCr	O
color	O
space	O
and	O
a	O
13.5MHz	O
sampling	O
frequency	O
for	O
pixels	B-Algorithm
.	O
</s>
<s>
For	O
the	O
parallel	O
format	O
,	O
a	O
25-pin	O
D-Sub	B-Protocol
connector	I-Protocol
pinout	O
and	O
ECL	O
logic	O
levels	O
are	O
defined	O
.	O
</s>
<s>
The	O
parallel	O
version	O
of	O
the	O
ITU-R	B-Device
BT.656	I-Device
protocol	O
is	O
also	O
used	O
in	O
many	O
TV	O
sets	O
between	O
chips	O
using	O
CMOS	B-Device
logic	O
levels	O
.	O
</s>
<s>
Typical	O
applications	O
include	O
the	O
interface	O
between	O
a	O
PAL/NTSC	O
decoder	O
chip	O
and	O
a	O
DAC	O
integrated	O
circuit	O
for	O
driving	O
a	O
CRT	B-Device
in	O
a	O
TV	O
set	O
.	O
</s>
<s>
A	O
BT.656	B-Device
data	O
stream	O
is	O
a	O
sequence	O
of	O
8-bit	O
or	O
10-bit	O
words	O
,	O
transmitted	O
at	O
a	O
rate	O
of	O
27Mword/s	O
.	O
</s>
<s>
Horizontal	O
scan	O
lines	O
of	O
video	O
pixel	B-Algorithm
data	O
are	O
delimited	O
in	O
the	O
stream	O
by	O
4-byte	O
long	O
SAV	O
(	O
Start	B-Device
of	I-Device
Active	I-Device
Video	I-Device
)	O
and	O
EAV	O
(	O
End	O
of	O
Active	O
Video	O
)	O
code	O
sequences	O
.	O
</s>
<s>
Individual	O
pixels	B-Algorithm
in	O
a	O
line	O
are	O
coded	O
in	O
YCbCr	O
format	O
.	O
</s>
<s>
After	O
an	O
SAV	O
code	O
(	O
4bytes	O
)	O
is	O
sent	O
,	O
the	O
first	O
8bits	O
of	O
Cb	O
(	O
chroma	O
U	O
)	O
data	O
are	O
sent	O
then	O
8bits	O
of	O
Y(luma )	O
,	O
followed	O
by	O
8bits	O
of	O
Cr	O
(	O
chroma	O
V	O
)	O
for	O
the	O
next	O
pixel	B-Algorithm
and	O
then	O
8bits	O
of	O
Y	O
.	O
</s>
<s>
To	O
reconstruct	O
full	O
resolution	O
Y	O
,	O
Cb	O
,	O
Cr	O
pixel	B-Algorithm
values	O
,	O
chroma	O
upsampling	O
must	O
be	O
used	O
.	O
</s>
