NDI Video

Although NDI® (NewTek’s Network Device Interface technology) is similar to Network Video in that the video stream is received over the network, there are enough differences to make it its own media type in WATCHOUT.

NDI video streams are identified by a name, which usually consists of a stream name and the name of the sending device, for example “Studio10 (BackupComputer)”. To preserve network bandwidth, the video streams are compressed using compression techniques which are part of NDI, and not generally compatible with any other types of video compression.

The compression used is lossy, like h264 and HAP, which means that there is some quality loss when using NDI. However, in almost all cases the loss is so small that it is not noticeable. One very important feature of the compression used in NDI is that it has no generation loss, meaning that you may compress and uncompress a video stream an infinite number of times, without any further loss of quality.

Assuming that there is an NDI source on the local network that you wish to incorporate into a WATCHOUT show, choose “Add NDI Video” from the Media menu. The dialog that appears lets you configure WATCHOUT for receipt, as shown below.

Name
The name of the source as it will appear in WATCHOUT’s user interface.

NDI® stream name
The name of the NDI stream you want to incorporate into the show. Select one from the list of all NDI sources that are visible on the local network. Alternatively, type in the name of the source.

Alternate NDI stream name
This is meant for specifying a backup NDI source. If the primary source fails, WATCHOUT will automatically switch to the alternate source. As soon as the primary source is back online, WATCHOUT will switch back. Using an alternate stream is optional.

Pixel format
This option gives the sender a hint of which pixel format is preferred by the receiver. The NDI sender is free to ignore this request. The default is YUVY, which gives the best compression and uses less bandwidth than BGRA. There is no support for an alpha channel in YUVY. If you need alpha, please use BGRA instead, but remember that the sender is free to ignore this request. BGRA uses more bandwidth, so YUVY is preferred at all times when there is no need for an alpha-channel.

Optimise for
There are three options here: Low Latency, Balanced and Smooth Playback. For Low latency, WATCHOUT keeps no queue of received frames. The frame displayed is always the latest frame received. This mode is sensitive to network hiccups, since if the continuous stream of frames is disrupted, WATCHOUT will have no new frame to display, resulting in the video freezing for a short amount of time. The Balanced mode keeps a short queue of frames for display. This increases the latency somewhat, but also makes the system less sensitive to network issues. Lastly, the Smooth Playback option keeps a larger queue of frames, which makes WATCHOUT even less sensitive to network issues, while increasing the latency further.

Preview
If Live Video is chosen, the video stream will be visible in the Stage window, for preview purposes. For the preview, a low-bandwidth (lower quality and lower resolution) stream is used, to preserve bandwidth.

Apply Frame Blending
If the display rate does not match the NDI stream rate, this option can be checked for smoother playback. As with any video media, frame blending will make the playback smoother, at the possible expense of a slightly blurrier appearance.

Dimensions
This is the size of the stream as it will be displayed by WATCHOUT. This resolution is also sent as a hint to the sender, which is free to ignore the request. If the resolution received is different, the frames will automatically be scaled to fit.

Audio

There is currently no support for NDI audio streams.

NDI-HX

Some NDI senders use a modified compression algorithm for enabling NDI to be used over Wifi and low-bandwidth connections. To use NDI-HX, the NDI-HX driver needs to be installed on all computers that will display the stream. This is available as an option in the WATCHOUT installer, or it may be downloaded from https://www.ndi.tv/tools/. In most cases there is no need to install this driver, as most streams are not HX-streams. NDI-HX uses less bandwidth, at the expense of more complex compression. Please bear in mind that many of the hardware boxes sending out NDI-HX are quite limited in processing power, and may not be able to deliver the stream to more than a few display servers simultaneously. This is not a limitation in WATCHOUT, but rather a limitation of the sender.

For Dataton media servers, the NDI HX driver will be installed when upgrading the WATCHOUT version by going online in the production software if – and only if – the NDI HX driver is installed on the production computer.

Multicast

To reduce the bandwidth requirements, many senders can be configured to use multicast, which means that only a single copy of the stream will exist on the network, and this stream will be received by all media servers that display the stream. For multicast to function properly, it is absolutely essential to use high quality network infrastructure. Use smart switches, and configure them to enable IGMP snooping for best results. Always try to keep the number of servers and devices connected to the network as low as possible and, preferably, use one switch with many ports instead of several smaller switches.

If not using multicast, one unique copy of the stream will be sent to each display server showing the stream. This can increase the network load dramatically.