<s>
Network	B-Protocol
Device	I-Protocol
Interface	I-Protocol
(	O
NDI	O
)	O
is	O
a	O
software	O
specification	O
developed	O
by	O
NewTek	O
that	O
enables	O
high-definition	O
video	O
to	O
be	O
delivered	O
,	O
received	O
,	O
and	O
communicated	O
over	O
a	O
computer	B-Architecture
network	I-Architecture
in	O
a	O
low-latency	O
,	O
high-quality	O
manner	O
.	O
</s>
<s>
By	O
default	O
,	O
NDI	O
uses	O
the	O
mDNS	B-Protocol
(	O
Bonjour	B-Application
/	O
Zeroconf	B-Application
)	O
discovery	O
mechanism	O
to	O
advertise	O
sources	O
on	O
a	O
local	O
area	O
network	O
,	O
such	O
that	O
NDI	O
receiving	O
devices	O
can	O
automatically	O
discover	O
and	O
offer	O
those	O
sources	O
.	O
</s>
<s>
It	O
also	O
supports	O
2	O
other	O
discovery	O
modes	O
(	O
NDI	O
Access	O
,	O
NDI	O
Discovery	O
Server	O
)	O
that	O
allow	O
for	O
operations	O
across	O
subnets	B-Protocol
and	O
without	O
mDNS	B-Protocol
.	O
</s>
<s>
NDI	O
3.x	O
has	O
options	O
to	O
use	O
UDP	O
multicast	O
or	O
unicast	O
with	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
(	O
FEC	O
)	O
instead	O
of	O
TCP	O
,	O
and	O
can	O
load	B-Application
balance	I-Application
streams	O
across	O
multiple	O
network	B-Protocol
interface	I-Protocol
controllers	I-Protocol
(	O
NICs	O
)	O
without	O
using	O
link	B-Architecture
aggregation	I-Architecture
.	O
</s>
<s>
Metadata	O
messages	O
can	O
be	O
sent	O
in	O
both	O
directions	O
allowing	O
the	O
sender	O
and	O
receiver	O
to	O
message	O
one	O
another	O
over	O
the	O
connection	O
with	O
arbitrary	O
metadata	O
in	O
XML	B-Protocol
form	O
.	O
</s>
<s>
The	O
NDI	O
software	B-Application
development	I-Application
kit	I-Application
(	O
SDK	O
)	O
is	O
available	O
for	O
Windows	O
,	O
Linux	O
and	O
MacOS	O
,	O
and	O
has	O
also	O
been	O
ported	O
to	O
iOS	O
,	O
tvOS	O
,	O
Android	O
,	O
Raspberry	O
Pi	O
,	O
and	O
FPGA	O
.	O
</s>
<s>
NDI	O
NDI	O
HX	O
NDI	O
HX2	O
SMPTE	O
SMPTE	O
2110	O
ASPEN	O
NMI	O
CDI	O
Transport	O
TCP/UDP/Multi-TCP/Reliable	O
UDP	O
UDP	O
(	O
TCP	O
)	O
TCP/UDP/Multi-TCP/Reliable	O
UDP	O
UDP	O
(	O
RTP	O
)	O
UDP	O
(	O
RTP	O
)	O
UDP	O
UDP	O
UDP	O
/	O
SRD	O
Image	O
format	O
Size	O
/	O
Aspect	O
Independent	O
Size	O
/	O
Aspect	O
Independent	O
Size	O
/	O
Aspect	O
Independent	O
SDI	O
Formats	O
only	O
Size	O
/	O
Aspect	O
Independent	O
Size	O
/	O
Aspect	O
Independent	O
Tally	O
Bidirectional	O
device	O
control	O
Integrated	O
Proxy	O
Integrated	O
alpha	B-Algorithm
channel	I-Algorithm
Compression	O
NDI	O
Codec	O
(	O
SHQ	O
0/2/7	O
)	O
NDI|HX	O
(	O
H.264	O
)	O
H.264/H.265	O
NONE	O
SMPTE	O
2110-22	O
spec	O
.	O
</s>
<s>
The	O
first	O
device	O
shown	O
using	O
NDI	O
was	O
the	O
NewTek	O
TriCaster	B-Device
which	O
delivered	O
an	O
NDI	O
feed	O
from	O
each	O
of	O
its	O
SDI	O
inputs	O
as	O
well	O
as	O
four	O
output	O
feeds	O
from	O
its	O
vision	O
mixer	O
.	O
</s>
<s>
The	O
TriCaster	B-Device
could	O
also	O
receive	O
up	O
to	O
two	O
NDI	O
sources	O
from	O
other	O
devices	O
(	O
increased	O
to	O
12	O
in	O
later	O
releases	O
and	O
up	O
to	O
44	O
in	O
NewTek	O
's	O
IP	O
Series	O
)	O
.	O
</s>
<s>
NewTek	O
had	O
previously	O
created	O
a	O
predecessor	O
of	O
NDI	O
called	O
AirSend	O
to	O
get	O
video	O
from	O
external	O
devices	O
into	O
their	O
TriCaster	B-Device
products	O
.	O
</s>
<s>
Another	O
early	O
adopter	O
of	O
NDI	O
was	O
VMix	B-Language
,	O
a	O
Windows-based	O
vision	O
mixer	O
which	O
offers	O
NDI	O
inputs	O
and	O
outputs	O
.	O
</s>
<s>
Later	O
in	O
2016	O
,	O
NewTek	O
delivered	O
NDI	O
2.0	O
which	O
added	O
features	O
including	O
support	O
for	O
service	O
discovery	O
across	O
subnets	B-Protocol
.	O
</s>
<s>
Version	O
3.4	O
of	O
FFmpeg	B-Library
added	O
input	O
and	O
output	O
support	O
for	O
NDI	O
when	O
optionally	O
compiled	O
by	O
the	O
end-user	O
to	O
a	O
non-open-source	O
NewTek	O
library	O
.	O
</s>
<s>
However	O
,	O
NewTek	O
was	O
later	O
found	O
to	O
be	O
redistributing	O
pre-compiled	O
binaries	O
of	O
FFmpeg	B-Library
that	O
incorporated	O
their	O
non-opensource	O
library	O
in	O
violation	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
,	O
causing	O
the	O
FFmpeg	B-Library
project	O
to	O
remove	O
NDI	O
support	O
from	O
their	O
codebase	O
in	O
March	O
2019	O
.	O
</s>
<s>
Version	O
Released	O
Features/Enhancements	O
1.0	O
April	O
2016	O
Initial	O
Release	O
2.0	O
Sept	O
2016	O
Cross	O
subnet	B-Protocol
support	O
via	O
Access	O
Manager	O
,	O
ARM	O
encoding	O
support	O
,	O
iOS	O
SDK	O
3.0	O
July	O
2017	O
NDI-HX	O
support	O
,	O
Option	O
for	O
multicast	O
transport	O
with	O
FEC	O
,	O
PTZ	O
support	O
.	O
</s>
<s>
3.6	O
July	O
2018	O
Packet	O
level	O
bonding	B-Architecture
improvements	O
.	O
</s>
<s>
NDI	O
was	O
designed	O
to	O
work	O
on	O
good	O
quality	O
gigabit	O
local	O
area	O
networks	O
using	O
TCP	O
and	O
Bonjour	B-Application
(	O
mDNS	B-Protocol
)	O
technologies	O
.	O
</s>
<s>
In	O
order	O
to	O
work	O
across	O
subnets	B-Protocol
that	O
do	O
n't	O
pass	O
mDNS	B-Protocol
,	O
NDI	O
supports	O
a	O
mechanism	O
known	O
as	O
NDI	O
Access	O
which	O
allows	O
manual	O
entry	O
of	O
the	O
IP	O
address	O
of	O
machines	O
on	O
other	O
subnets	B-Protocol
which	O
may	O
be	O
running	O
NDI	O
sources	O
.	O
</s>
<s>
Some	O
NDI	O
adopters	O
have	O
run	O
the	O
protocol	O
across	O
fibre	O
connections	O
up	O
to	O
15km	O
,	O
although	O
NDI	O
's	O
use	O
of	O
the	O
TCP	B-Protocol
protocol	I-Protocol
makes	O
it	O
less	O
suitable	O
for	O
long-distance	O
,	O
high-latency	O
connections	O
due	O
to	O
factors	O
such	O
as	O
bandwidth-delay	O
product	O
and	O
TCP	B-Protocol
packet	I-Protocol
loss	I-Protocol
recovery	I-Protocol
.	O
</s>
<s>
NDI	O
,	O
when	O
running	O
on	O
x86	O
architectures	O
,	O
requires	O
CPUs	O
that	O
include	O
the	O
SSSE3	B-General_Concept
instruction	O
set	O
.	O
</s>
<s>
While	O
not	O
a	O
requirement	O
,	O
NDI	O
will	O
take	O
advantage	O
of	O
Advanced	B-General_Concept
Vector	I-General_Concept
Extensions	I-General_Concept
(	O
AVX	O
)	O
and	O
AVX2	O
instructions	O
sets	O
for	O
additional	O
performance	O
.	O
</s>
<s>
NDI	O
supports	O
arbitrary	O
metadata	O
as	O
XML	B-Protocol
blocks	O
,	O
embedded	O
in	O
video	O
and	O
audio	O
frames	O
,	O
as	O
well	O
as	O
stand-alone	O
metadata	O
frames	O
.	O
</s>
