NDI (Network Device Interface)

Newtek logo NDI is an open-standard protocol developed by NewTek for connecting multiple devices via IP network infrastructure and sharing video, audio and metadata with low latency. It uses (highly) variable bit-rate video compression to minimise network bandwidth, when possible, yet maintain high video quality.
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ZEN NDI GradBG - Colour Gradient Background generator

Colour Gradient background generator for NDI - from ZEN Computer Services

The basic functionality is in generating a 4-way gradient-filled image using selectable colours for the four corners of the rectangle, although pairs can be set to the same value in order to achieve a simple 2-way gradient. The gradient image can either remain static or the colours can rotate in a clockwise (CW) or anticlockwise (CCW) direction. A slider control adjusts the period between colour changes (i.e. faster rotational speed as the slider moves to the right).

ZEN NDI GradBG user interface - NDI software from ZEN Computer Services The gradient image can either fill the screen, be horizontally (H-Split) or vertically mirrored (V-Split) as two half-size rectangles, or be mirrored both horizontally and vertically (in Quad mode) using quarter-size rectangles. The Cloud overlay option adds a fixed fractal noise pattern, self-keyed over the background.

There are five Presets which hold different configurations (colours, patterns, etc). The Paste button will copy the last used preset to the current one (e.g. to copy number 3 to number 5, select 3 then select 5 and click on Paste)

On exit, a "last.gbg" file will be created with the current group of five presets, plus it's possible to save a "default.gbg" file from the main right-click drop-down menu in the title bar. If the default file exists, it will be loaded on start-up. Click the "Load last" button to load the last used preset group. Multiple instances of the app can be run on the same PC, with the NDI ident names being sequentially auto-numbered. The "watermark" logo will disappear after several minutes of use.

Download NDIGradBG v1.0.0.4 here   (from Sep-17)

ZEN NDI RTx (NDI Receiver-Transmitter)

One of the "features" of NewTek's NDI is that connections between devices are all point-to-point, such that if two receiving devices are connected to a single source sending video, then two streams are required - meaning twice the bandwidth of a single stream. The more connections you add, the more bandwidth is required. Given that NDI is intended for production environments rather than mass-audience video streaming, this is not usually a problem, but it may be desirable for a number of remote stations to be able to monitor a single source - the main output from a switcher, for example. In these circumstances there could be a high bandwidth requirement over the network connection from that source, potentially more than a single node can handle. One solution is to retransmit the NDI stream from another PC on the network via the equivalent of a "Relay" or "Repeater" transmitter (as used in TV/Radio transmission). A kind of NDI "Distribution Amp" if you like.

My NDI-RTx was created because I wanted something to run on a remote PC to perform an "NDI loopback" so I could monitor the effects of a round-trip over a network, measured on the same PC as the NDI source.

After I started using it I then realised that something like this can be used as a sort of "NDI CDN" to distribute network bandwidth by creating remote "splitter-nodes" at various locations and offload work from the switcher PC. Bear in mind that this utility was created for in-house testing so may not be the most robust code, and given that it was intended for simple loopback applications it has not been tested with large numbers of clients, but if anyone out there would like to do some tests with it you can download a test version below. Unzip into it's own folder and install the VisualC libraries (DLLs) if needed and it should be good to go.

Download NDI RTx v1.0.3.1 here   (from Sep-17)

The current edition, v1.0.3.0, now includes a freeze-frame function, local audio monitoring and a video confidence monitor, has been recompiled with the NDI v2.0 code, and looks like this:-

ZEN RTx NDI receiver-transmitter utility GUI

Hopefully, usage is fairly straightforward and there's a ReadMe file in the download with further notes.

After you open the app it should start to detect active NDI source names. Sources will subsequently be added/removed automatically or you can press the Disconnect button to re-trigger checking.
Note that "Exclude local sources" is ticked by default.

Click on a Source in the list to make a connection. You will see some stats about the connected source along the top of the window:- IP address/port, Source name, video resolution/frame-rate, audio channels/sample-rate and timcode (if present). The right-hand indicator light will be purple for a video+audio source, red for video-only, blue for audio-only.

To select a different source it is necessary to first Disconnect the existing source. The connection indicator light should go out and the top part of the display will look a bit like this when no source is connected:-

ZEN NDI-RTx relay receiver transmitter app for NewTek NDI

Note that multiple copies of NDI-RTx can be run on the same PC, each of which will be allocated a different NDI Source name. (eg the first copy will have an NDI name ending RTx 1, then RTx 2, etc)

The more recent versions also include an audio meter/monitor function (for Ch1+2), as above. Click on the upper/middle/lower part of the speaker icon to get full-level/dimmed/muted audio output.

This software is supplied "as-is", with no warranty or guarantees of being fit for any particular purpose!

Martin Kay - May 2016 - Apr 2017


The NDI "No Audio" Meter

A simple Red-Amber-Green audio display designed to a provide an alert when the audio level of the selected NDI audio stream falls below a certain level. Detection thresholds can be adjusted and the No Audio state both flashes red and generates audio beeps. Also detects of breaks in the stream from the selected NDI source.

For a limited period, the old version ( of NDINoAudioMeter is available for download from here. See the included ReadMe file for further info. The link for the current version is below.

Revised version now includes a video preview window and has been recompiled using the NDI2.0 code. Functionality is otherwise the same as the previous version, albeit with a rearranged layout to the controls.

Download from ZEN Download NDINoAudioMeter v1.1.0.2 here   (from Sep-17)

Work-in-progress - Quad NDI input sources from Magewell Pro Capture cards

An alternative to NewTek's NDI Connect (Pro), explicitly designed to expose the hardware video processing features of Magewell's Pro Capture family of PCIe cards. Use a Pro Capture Quad card to create four NDI sources, for example.

Video demo/introduction can be downloaded from here

NDIZender is based on the NDI Sender example application that was introduced into the Magewell Pro Capture SDK for Windows at the start of September 2016. Prior to that I'd been developing the quad-input "NDI sender" (above), but in many ways the SDK example looked more complete - it had audio input & monitoring for example - so I thought I'd take a bit of time out and see if I could tidy it up and add a few important features, like support for PAL frame-rates, all of which looked simple enough.

Over two months later, after much "tidying up", some debugging of underlying functionality, and the addition of many new controls and features, NDIZender bears only a passing resemblance to the original in the Magewell SDK.

The beta version from Dec-2016 can be downloaded below, along with other NDI apps. 

Download from ZEN Download NDIZender (and others) here   (from Dec-16)

An NDI Routing Switcher

During the Christmas break I was experimenting with the Routing functions introduced in v2.0 of the NDI SDK. These functions allow the creation of software routers for NDI signals which can effectively switch between NDI sources with no added latency and virtually zero CPU usage. As a proof-of-concept sample application I created a 6in-2out switcher - which seems to work as expected and, for some applications, if only as an auxiliary switcher, could be a really useful tool for some people. Note that the switching can be done from anywhere on the network, and that the actual NDI streams do not have to pass through the computer running the Router software, which effectively just acts a "front panel remote" to the virtual NDI router.

Download NDIRouter v1.0.0.4 here   (from 17-Jul-17)

In the illustration below, the router/switcher is configured like a 6-input cuts-only A-B switcher, with Preview (B) & Program (A) buses/outputs and a Cut button which swaps the contents of the busses.

Martin will be helping Magewell on their booth at IBC this year- number A84 in Hall 8.

As a result, the ZEN office in Salford will be closed from Thursday 14th
and open again on Wednesday 20th September. During this period, email response may be slower than normal, but small orders for Magewell USB Capture devices will be processed as normal if placed via Amazon.co.uk

What we're about . . .      ZEN is not a traditional Audio-Visual dealer who started selling computers, nor is it a computer shop that also sells video products. You won't get any salesmen giving you the "hard-sell" when you call, just straightforward advice and information - which for some callers is the knowledge that they don't need to buy whatever it is they thought they needed! Above all you'll be dealing with someone with a wide range of experience and knowledge of both PCs and video production. We're not the biggest, nor necessarily the cheapest, but we are one of the longest established computer/video specialists in the UK.

Company history . . .      ZEN was started in the 1980s by Martin Kay, then working for ITV at Granada's Manchester studios, who built his first 6502-based computer in 1979 from an Ohio Scientific kit, bought in the USA whilst working as a Sound Recordist on a film shoot for World In Action. With the advent of the Amiga, which could be gen-locked to a video source, Martin started writing a variety of video-related software. This included subtitling & tele-prompting, ident clocks, scoring software for sports & gameshows, and specialist software to mimic other computer displays for use in TV film dramas like Cracker, Prime Suspect and A Touch of Frost. Martin left Granada in 1993 to concentrate on his computer-video activities with ZEN, following a natural path into non-linear editing systems, for many years the main business activity, although he still maintains an active interest in video production.

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Revised: 12 September, 2017