Network Device Interface

Network Device Interface (NDI) is a royalty free standard 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 .

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, Raspberry PI, and FPGA. There is 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 using an arbitrarily selected TCP port from a range of ports on the NDI send host. 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. This directional metadata system allows for functionality such as active tally information fed back to sources to understand that they are on-air (program / preview). NDI also allows senders to determine the number of connected receivers, so they can skip unnecessary processing and network bandwidth utilisation when there are no NDI receiver clients connected.

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.

*The TICO codec can be used to compress UHD by 4:1 so an encoded stream can be carried along a SMPTE 2022-6 channel at the same uncompressed bandwidth as HD. SMPTE 2110 with TR-03 also offers the potential to use TICO. This requires a proprietary encoder and decoder which are generally implemented as silicon on each end. * * NDI 3.0 supports TCP and also UDP including Multicast as appropriate

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