Network Device Interface (NDI) is an open protocol developed by NewTek to enable video-compatible products to communicate, deliver, and receive broadcast quality video in a high quality, low latency manner that is frame-accurate and suitable for switching in a live production environment. The protocol is designed to be highly robust and is used in many network-connected video devices. It has been widely adopted and the installed based for NDI exceeds 1 million users
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Technology
Whilst the NDI technology has been developed by NewTek it is made available to anyone with a royalty-free license, and has been widely adopted by many broadcast vendors, including those sometimes seen as competition for NewTek's own products. A free code library and examples is available for Windows, Linux and macOS. NDI has also been ported to iOS, Android and Raspberry PI, and work is ongoing to deliver NDI using FPGAs. There are also a range of free NDI tools for end users provided by NewTek, Sienna, VMix and others.
Unlike other professional IP Video protocols such as SMPTE2022-6 and ASPEN which require 10 Gigabit networks, NDI is designed to run over existing 1 Gigabit networks allowing easy adoption of the protocol without new infrastructure. This is achieved through the use of video data compression with the NDI codec which delivers 1080 full HD video at VBR data rates typically around 100mBit/sec.
NDI uses the mDNS (Bonjour / Zeroconf) discovery mechanism to advertise sources on a local area network, such that NDI receiving devices can automatically discover and offer those sources. Sources are created randomly using one of a range of ports. When a source is requested a TCP connection is established on the appropriate port with the NDI receiver connecting to the NDI sender.
NDI carries video, multichannel uncompressed audio and metadata. Metadata messages can be sent in both directions allowing the sender and receiver to message one another over the connection with arbitrary metadata in XML form
Comparison of NDI With Other Protocols
Other IP Video protocols emerging for use in professional video production (rather than IP Video used for distribution to end users) include SMPTE 2022, SMPTE2110, ASPEN and Sony NMI. There are clear differences in the technology used by these protocols.
History
NDI was publicly revealed by NewTek on 8 September 2015 and was demonstrated at the IBC broadcast exhibition in Amsterdam that week. The first device shown using NDI was the NewTek TriCaster which delivered an NDI feed from each of its SDI inputs as well as 4 output feeds from its vision mixer. TriCaster could also receive up to 2 NDI sources from other devices (increased to 12 in later releases and up to 44 in NewTek's IP Series ).
NDI devices from other vendors followed during 2016. The first 3rd party products came from Gallery Sienna and included an NDI signal generator for macOS, a desktop scan converter for macOS and the NDICam camera app for iPhone which delivers a native NDI stream from iOS devices.
NewTek had previously created a predecessor of NDI called AirSend to get video from external devices into their TriCaster products. AirSend had been implemented by a number of CG manufacturers including VizRT and Chyron. In order to quickly bring these products into the NDI space, NewTek created a new driver to replace the existing AirSend driver, which could be installed on these existing AirSend compatible devices, instantly converting them to NDI compatible devices with no change required by the original CG vendors.
Another early adopter of NDI was VMix, a Windows based vision mixer which offers NDI inputs and outputs. The biggest increase in the NDI installed base came when live streaming application XSplit added support for NDI.
Later in 2016, NewTek delivered NDI 2.0 which added features including support for service discovery across subnets.
Use in Wifi and Wide Area Networks
NDI was designed to work on good quality gigabit local area networks using TCP and Bonjour technologies. Mobile apps like NDICam have shown that NDI can also work well on Wifi networks, although the need for c. 100mBit communications requires very good quality communication between the device and the Wifi router to achieve full frame rates.
Some NDI adopters have run the protocol across medium distance Fibre connections up to 15 km, although NDI's use of the TCP protocol make it less suitable for longer distance, high latency connections due to issues of Bandwidth Delay Product and TCP packet loss recovery. To provide an extension of NDI to wide area networks, the NDI.Cloud protocol uses node gateways in each LAN to bridge NDI sources across continents.
Adoption
The NDI Protocol has been widely adopted by a diverse variety of software and hardware vendors. The table below includes a list of shipping products known to support the NDI Protocol