<s>
Serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
(	O
SDI	O
)	O
is	O
a	O
family	O
of	O
digital	O
video	O
interfaces	B-Application
first	O
standardized	O
by	O
SMPTE	O
(	O
The	O
Society	O
of	O
Motion	O
Picture	O
and	O
Television	O
Engineers	O
)	O
in	O
1989	O
.	O
</s>
<s>
For	O
example	O
,	O
ITU-R	B-Device
BT.656	I-Device
and	O
SMPTE	O
259M	O
define	O
digital	O
video	O
interfaces	B-Application
used	O
for	O
broadcast-grade	O
video	O
.	O
</s>
<s>
A	O
related	O
standard	O
,	O
known	O
as	O
high-definition	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
(	O
HD-SDI	B-Protocol
)	O
,	O
is	O
standardized	O
in	O
SMPTE	O
292M	O
;	O
this	O
provides	O
a	O
nominal	O
data	O
rate	O
of	O
1.485Gbit/s	O
.	O
</s>
<s>
Dual	O
link	O
HD-SDI	B-Protocol
consists	O
of	O
a	O
pair	O
of	O
SMPTE	O
292M	O
links	O
,	O
standardized	O
by	O
SMPTE	O
372M	O
in	O
1998	O
;	O
this	O
provides	O
a	O
nominal	O
2.970Gbit/s	O
interface	O
used	O
in	O
applications	O
(	O
such	O
as	O
digital	O
cinema	O
or	O
HDTV	B-Device
1080P	O
)	O
that	O
require	O
greater	O
fidelity	O
and	O
resolution	O
than	O
standard	O
HDTV	B-Device
can	O
provide	O
.	O
</s>
<s>
3G-SDI	B-Protocol
(	O
standardized	O
in	O
SMPTE	O
424M	O
)	O
consists	O
of	O
a	O
single	O
2.970Gbit/s	O
serial	O
link	O
that	O
allows	O
replacing	O
dual	O
link	O
HD-SDI	B-Protocol
.	O
</s>
<s>
6G-SDI	B-Protocol
and	O
12G-SDI	B-Protocol
standards	O
were	O
published	O
on	O
March	O
19	O
,	O
2015	O
.	O
</s>
<s>
These	O
standards	O
are	O
used	O
for	O
transmission	O
of	O
uncompressed	B-Device
,	I-Device
unencrypted	I-Device
digital	I-Device
video	I-Device
signals	O
(	O
optionally	O
including	O
embedded	O
audio	O
and	O
time	O
code	O
)	O
within	O
television	O
facilities	O
;	O
they	O
can	O
also	O
be	O
used	O
for	O
packetized	O
data	O
.	O
</s>
<s>
SDI	O
and	O
HD-SDI	B-Protocol
are	O
usually	O
available	O
only	O
in	O
professional	O
video	O
equipment	O
because	O
various	O
licensing	O
agreements	O
restrict	O
the	O
use	O
of	O
unencrypted	O
digital	O
interfaces	B-Application
,	O
such	O
as	O
SDI	O
,	O
prohibiting	O
their	O
use	O
in	O
consumer	O
equipment	O
.	O
</s>
<s>
Several	O
professional	O
video	O
and	O
HD-video	O
capable	O
DSLR	B-Device
cameras	I-Device
and	O
all	O
uncompressed	B-Device
video	I-Device
capable	O
consumer	O
cameras	O
use	O
the	O
HDMI	B-Protocol
interface	O
,	O
often	O
called	O
clean	B-Device
HDMI	I-Device
.	O
</s>
<s>
There	O
are	O
various	O
mod	O
kits	O
for	O
existing	O
DVD	B-Device
players	I-Device
and	O
other	O
devices	O
,	O
which	O
allow	O
a	O
user	O
to	O
add	O
a	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
to	O
these	O
devices	O
.	O
</s>
<s>
The	O
various	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
standards	O
all	O
use	O
(	O
one	O
or	O
more	O
)	O
coaxial	O
cables	O
with	O
BNC	B-Protocol
connectors	I-Protocol
,	O
with	O
a	O
nominal	O
impedance	O
of	O
75	O
ohms	O
.	O
</s>
<s>
Using	O
equalization	B-Algorithm
at	O
the	O
receiver	O
,	O
it	O
is	O
possible	O
to	O
send	O
270Mbit/s	O
SDI	O
over	O
without	O
use	O
of	O
repeaters	O
,	O
but	O
shorter	O
lengths	O
are	O
preferred	O
.	O
</s>
<s>
Data	O
is	O
encoded	O
in	O
NRZI	O
format	O
,	O
and	O
a	O
linear	B-Architecture
feedback	I-Architecture
shift	I-Architecture
register	I-Architecture
is	O
used	O
to	O
scramble	O
the	O
data	O
to	O
reduce	O
the	O
likelihood	O
that	O
long	O
strings	O
of	O
zeroes	O
or	O
ones	O
will	O
be	O
present	O
on	O
the	O
interface	O
.	O
</s>
<s>
The	O
143	O
and	O
177Mbit/s	O
interfaces	B-Application
were	O
intended	O
for	O
transmission	O
of	O
composite-encoded	O
(	O
NTSC	O
or	O
PAL	B-Language
)	O
video	O
digitally	O
,	O
and	O
are	O
now	O
considered	O
obsolete	O
.	O
</s>
<s>
For	O
enhanced	O
definition	O
applications	O
(	O
mainly	O
525P	O
)	O
,	O
there	O
are	O
several	O
540Mbit/s	O
interfaces	B-Application
defined	O
,	O
as	O
well	O
as	O
an	O
interface	O
standard	O
for	O
a	O
dual-link	O
270Mbit/s	O
interface	O
.	O
</s>
<s>
For	O
HDTV	B-Device
applications	O
,	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
is	O
defined	O
by	O
SMPTE	O
292M	O
.	O
</s>
<s>
For	O
very	O
high-definition	O
applications	O
,	O
requiring	O
greater	O
resolution	O
,	O
frame	O
rate	O
,	O
or	O
color	O
fidelity	O
than	O
the	O
HD-SDI	B-Protocol
interface	O
can	O
provide	O
,	O
the	O
SMPTE	O
372M	O
standard	O
defines	O
the	O
dual	O
link	O
interface	O
.	O
</s>
<s>
In	O
addition	O
to	O
optical	O
specification	O
,	O
ST	O
297	O
also	O
mandates	O
laser	O
safety	O
testing	O
and	O
that	O
all	O
optical	O
interfaces	B-Application
are	O
labelled	O
to	O
indicate	O
safety	O
compliance	O
,	O
application	O
and	O
interoperability	O
.	O
</s>
<s>
For	O
all	O
serial	B-Protocol
digital	I-Protocol
interfaces	I-Protocol
(	O
excluding	O
the	O
obsolete	O
composite	O
encodings	O
)	O
,	O
the	O
native	O
color	O
encoding	O
is	O
4:2:2	O
YCbCr	O
format	O
.	O
</s>
<s>
In	O
the	O
HD-SDI	B-Protocol
and	O
dual	O
link	O
interfaces	B-Application
,	O
synchronization	O
packets	O
must	O
occur	O
simultaneously	O
in	O
both	O
the	O
Y	O
and	O
C	O
datastreams	O
.	O
</s>
<s>
In	O
SD-SDI	B-Protocol
and	O
enhanced	O
definition	O
interfaces	B-Application
,	O
there	O
is	O
only	O
one	O
datastream	O
,	O
and	O
thus	O
only	O
one	O
synchronization	O
packet	O
at	O
a	O
time	O
.	O
</s>
<s>
Likewise	O
,	O
the	O
packet	O
appearing	O
immediately	O
before	O
the	O
start	O
of	O
the	O
active	O
video	O
has	O
H	O
set	O
to	O
0	O
;	O
this	O
is	O
the	O
Start	B-Device
of	I-Device
Active	I-Device
Video	I-Device
or	O
SAV	O
packet	O
.	O
</s>
<s>
In	O
progressive	B-Device
scan	I-Device
formats	O
,	O
the	O
F	O
bit	O
is	O
always	O
set	O
to	O
zero	O
.	O
</s>
<s>
In	O
the	O
high	O
definition	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
(	O
and	O
in	O
dual-link	O
HD	O
)	O
,	O
additional	O
check	O
words	O
are	O
provided	O
to	O
increase	O
the	O
robustness	O
of	O
the	O
interface	O
.	O
</s>
<s>
The	O
CRC	O
and	O
line	O
counts	O
are	O
not	O
provided	O
in	O
the	O
SD	O
and	O
ED	O
interfaces	B-Application
.	O
</s>
<s>
In	O
SD	O
interfaces	B-Application
,	O
where	O
there	O
is	O
only	O
one	O
datastream	O
,	O
the	O
0th	O
sample	O
is	O
a	O
Cb	O
sample	O
;	O
the	O
1st	O
sample	O
a	O
Y	O
sample	O
,	O
the	O
2nd	O
sample	O
a	O
Cr	O
sample	O
,	O
and	O
the	O
third	O
sample	O
is	O
the	O
Y	O
 '	O
sample	O
;	O
the	O
pattern	O
repeats	O
from	O
there	O
.	O
</s>
<s>
In	O
HD	O
interfaces	B-Application
,	O
each	O
datastream	O
has	O
its	O
own	O
sample	O
numbering	O
—	O
so	O
the	O
0th	O
sample	O
of	O
the	O
Y	O
datastream	O
is	O
the	O
Y	O
sample	O
,	O
the	O
next	O
sample	O
the	O
Y	O
 '	O
sample	O
,	O
etc	O
.	O
</s>
<s>
Note	O
that	O
this	O
behavior	O
differs	O
somewhat	O
from	O
analog	O
video	O
interfaces	B-Application
,	O
where	O
the	O
line	O
transition	O
is	O
deemed	O
to	O
occur	O
at	O
the	O
sync	O
pulse	O
,	O
which	O
occurs	O
roughly	O
halfway	O
through	O
the	O
horizontal	O
blanking	O
region	O
.	O
</s>
<s>
Link	O
numbering	O
is	O
only	O
an	O
issue	O
in	O
multi-link	O
interfaces	B-Application
.	O
</s>
<s>
When	O
the	O
two	O
links	O
are	O
combined	O
,	O
the	O
result	O
is	O
a	O
progressive-scan	B-Device
picture	O
at	O
the	O
higher	O
frame	O
rate	O
.	O
</s>
<s>
Both	O
the	O
HD	O
and	O
SD	O
serial	O
interfaces	B-Application
provide	O
for	O
16	O
channels	O
of	O
embedded	O
audio	O
.	O
</s>
<s>
The	O
two	O
interfaces	B-Application
use	O
different	O
audio	O
encapsulation	O
methods	O
—	O
SD	O
uses	O
the	O
SMPTE	O
272M	O
standard	O
,	O
whereas	O
HD	O
uses	O
the	O
SMPTE	O
299M	O
standard	O
.	O
</s>
<s>
Typically	O
,	O
48kHz	O
,	O
24-bit	O
(	O
20-bit	O
in	O
SD	O
,	O
but	O
extendable	O
to	O
24	O
bit	O
)	O
PCM	B-Algorithm
audio	I-Algorithm
is	O
stored	O
,	O
in	O
a	O
manner	O
directly	O
compatible	O
with	O
the	O
AES3	O
digital	O
audio	O
interface	O
.	O
</s>
<s>
As	O
the	O
standard	O
definition	O
interface	O
carries	O
no	O
checksum	O
,	O
CRC	O
,	O
or	O
other	O
data	O
integrity	O
check	O
,	O
an	O
EDH	O
(	O
Error	B-Device
Detection	I-Device
and	I-Device
Handling	I-Device
)	O
packet	O
may	O
be	O
optionally	O
placed	O
in	O
the	O
vertical	O
interval	O
of	O
the	O
video	O
signal	O
.	O
</s>
<s>
In	O
early	O
versions	O
of	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
,	O
it	O
was	O
always	O
possible	O
to	O
uniquely	O
determine	O
the	O
video	O
format	O
by	O
counting	O
the	O
number	O
of	O
lines	O
and	O
samples	O
between	O
H	O
and	O
V	O
transitions	O
in	O
the	O
TRS	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
dual	O
link	O
interfaces	B-Application
,	O
and	O
segmented-frame	O
standards	O
,	O
this	O
is	O
no	O
longer	O
possible	O
;	O
thus	O
the	O
VPID	O
standard	O
(	O
defined	O
by	O
SMPTE	O
352M	O
)	O
provides	O
a	O
way	O
to	O
uniquely	O
and	O
unambiguously	O
identify	O
the	O
format	O
of	O
the	O
video	O
payload	O
.	O
</s>
<s>
Several	O
color	O
encodings	O
are	O
possible	O
in	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
.	O
</s>
<s>
The	O
dual-link	O
and	O
3Gbit/s	O
interfaces	B-Application
additionally	O
support	O
other	O
color	O
encodings	O
besides	O
4:2:2	O
YCbCr	O
,	O
namely	O
:	O
</s>
<s>
The	O
various	O
versions	O
of	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
support	O
numerous	O
video	O
formats	O
.	O
</s>
<s>
These	O
formats	O
are	O
highly	O
compatible	O
with	O
NTSC	O
and	O
PAL-B/G/D/K/I	O
systems	O
respectively	O
;	O
and	O
the	O
terms	O
NTSC	O
and	O
PAL	B-Language
are	O
often	O
(	O
incorrectly	O
)	O
used	O
to	O
refer	O
to	O
these	O
formats	O
.	O
</s>
<s>
(	O
PAL	B-Language
is	O
a	O
composite	O
color	O
encoding	O
scheme	O
,	O
and	O
the	O
term	O
does	O
not	O
define	O
the	O
line-standard	O
,	O
though	O
it	O
is	O
most	O
usually	O
encountered	O
with	O
625i	O
)	O
while	O
the	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
—	O
other	O
than	O
the	O
obsolete	O
143Mbit/s	O
and	O
177Mbit/s	O
forms	O
-	O
is	O
a	O
component	O
standard	O
.	O
</s>
<s>
The	O
various	O
540Mbit/s	O
interfaces	B-Application
support	O
525p	O
and	O
625p	O
formats	O
.	O
</s>
<s>
The	O
nominal	O
1.49Gbit/s	O
interfaces	B-Application
support	O
most	O
high-definition	O
video	O
formats	O
.	O
</s>
<s>
The	O
2.97	O
Gbit/s	O
dual	O
link	O
HD	O
interface	O
supports	O
1080/60p	O
,	O
1080/59.94p	O
,	O
and	O
1080/50p	O
,	O
as	O
well	O
as	O
4:4:4	O
encoding	O
,	O
greater	O
color	O
depth	O
,	O
RGB	O
encoding	O
,	O
alpha	B-Algorithm
channels	I-Algorithm
,	O
and	O
nonstandard	O
resolutions	O
(	O
often	O
encountered	O
in	O
computer	O
graphics	O
or	O
digital	O
cinema	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
regular	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
described	O
here	O
,	O
there	O
are	O
several	O
other	O
similar	O
interfaces	B-Application
which	O
are	O
similar	O
to	O
,	O
or	O
are	O
contained	O
within	O
,	O
a	O
serial	B-Protocol
digital	I-Protocol
interface	I-Protocol
.	O
</s>
<s>
ASI	O
is	O
popular	O
way	O
to	O
transport	O
broadcast	B-Operating_System
programs	O
from	O
the	O
studio	O
to	O
the	O
final	O
transmission	O
equipment	O
before	O
it	O
reaches	O
viewers	O
sitting	O
at	O
home	O
.	O
</s>
<s>
The	O
ASI	O
standard	O
is	O
part	O
of	O
the	O
Digital	B-Application
Video	I-Application
Broadcasting	I-Application
(	O
DVB	B-Application
)	O
standard	O
.	O
</s>
<s>
The	O
standard	O
SMPTE	O
349M	O
:	O
Transport	O
of	O
Alternate	O
Source	O
Image	O
Formats	O
through	O
SMPTE	O
292M	O
,	O
specifies	O
a	O
means	O
to	O
encapsulate	O
non-standard	O
and	O
lower-bitrate	O
video	O
formats	O
within	O
an	O
HD-SDI	B-Protocol
interface	O
.	O
</s>
<s>
This	O
standard	O
allows	O
,	O
for	O
example	O
,	O
several	O
independent	O
standard-definition	O
video	O
signals	O
to	O
be	O
multiplexed	O
onto	O
an	O
HD-SDI	B-Protocol
interface	O
,	O
and	O
transmitted	O
down	O
one	O
wire	O
.	O
</s>
<s>
The	O
HDMI	B-Protocol
interface	O
is	O
a	O
compact	O
audio/video	O
interface	O
for	O
transferring	O
uncompressed	B-Device
video	I-Device
data	O
and	O
compressed/uncompressed	O
digital	O
audio	O
data	O
from	O
an	O
HDMI-compliant	O
device	O
to	O
a	O
compatible	O
computer	B-Device
monitor	I-Device
,	O
video	B-Device
projector	I-Device
,	O
digital	B-Application
television	I-Application
,	O
or	O
digital	O
audio	O
device	O
.	O
</s>
<s>
It	O
is	O
mainly	O
used	O
in	O
the	O
consumer	O
area	O
,	O
but	O
increasingly	O
used	O
in	O
professional	O
devices	O
including	O
uncompressed	B-Device
video	I-Device
,	O
often	O
called	O
clean	B-Device
HDMI	I-Device
.	O
</s>
<s>
The	O
CoaXPress	B-Device
standard	O
is	O
another	O
high-speed	O
digital	O
interface	O
,	O
originally	O
design	O
for	O
industrial	O
camera	O
interfaces	B-Application
.	O
</s>
<s>
The	O
data	O
rates	O
for	O
CoaXPress	B-Device
go	O
up	O
to	O
12.5Gbit/s	O
over	O
a	O
single	O
coaxial	O
cable	O
.	O
</s>
