AJA Video Provides Flexible Bridge From SDI To NDI And Back Again

As broadcast facilities and other organizations that use media to educate and inform continue to carefully make the move to video over IP, they currently face two main options, with a range of others in the wings. ​They may opt for a full SMPTE ST 2110 design that leverages uncompressed pristine quality video for higher profile productions or lightly compressed NDI networking, which brings with it less costs and easy access to an expanding ecosystem of compliant products and systems.

With hundreds of manufacturers and more than 3,000 NDI products now available to the market, NDI is helping to expand the IP video transport universe and has become established in sectors like enterprise, government, education, Houses of Worship, college sports, and even within Broadcast pipelines for a range of OTT and secondary delivery needs. Many of these users, however, started in the SDI world and will continue to use SDI in some capacity for several years, due to previous infrastructure investments, so the need for high quality conversion gear for moving signals between the two environments has become critical.

NDI Is Widely Embraced, Even Among SDI Facilities
First introduced in 2015, NDI has become a widely accepted audio/video networking protocol for IP transmission and live production using standard LAN networking—both among equipment vendors, as well as customers across the broadcast, production, and proAV markets. Leveraging methods as part of the standardized protocol allows users to easily make connections to an IP network while also finding a device within a networked infrastructure. The protocol preserves visual quality, frame accuracy, and source synchronization to keep productions looking good and running smoothly.

NDI video is sent and received as a compressed stream in the UYVY or P216 4:2:2 format, or optionally UYVA 4:2:2, when including an alpha channel. Video can be 8-bit (UYVY) or 16-bit (P216) color depth. There are no limits to frames per second or resolution, except for what specific hardware can handle. The NDI protocol also supports multicast video sources using multicast UDP with forwards error correction to protect against packet loss. Multicasting allows for a single NDI source to be delivered to multiple receivers by replicating the NDI packets from the sender to any number of receivers.

Targeting this expanding array of NDI applications and users, AJA Video Systems has introduced a new signal conversion hub (gateway) called BRIDGE NDI 3G. The 1RU appliance supports multi-channel 4K and HD workflows and is designed to help broadcast, production, and proAV professionals move between various platforms, protocols, and connectivity types.

A Migration/Conversion Tool
Bryce Button, Director of Product Marketing at AJA Video Systems, calls the new BRIDGE NDI 3G gateway “a powerful migration product for moving to IP cost effectively,” enabling users to create IP islands within an SDI facility to get started. It’s designed to fit seamlessly into any existing NDI or SDI workflow and help users to easily integrate a range of 3G-SDI sources into NDI workflows and vice versa, while making the most out of new and existing gear.

BRIDGE NDI 3G converts SDI camera and playout sources into NDI streams, enabling simple integration into NDI-supported workflows, including virtualized productions leveraging NDI-based switchers. Using a common network, these sources can be located anywhere within a facility, allowing seamless integration of various production islands into a unified workflow. Conversely, NDI streams can be converted back into SDI ecosystems via the gateway’s configurable I/O, allowing NDI signals to move back into SDI routing systems and traditional baseband workflows. Bridge NDI 3G’s flexibility means that it can be used to simultaneously convert SDI to NDI and NDI to SDI, or in the case of dedicated workflows can support all encode (SDI->NDI), or all decode (NDI->SDI).

Reference for SDI output is provided via Dual Analog Color Black or HD Tri-level sync connectors on the rear of BRIDGE NDI for high quality timing and stability, which is particularly important if sending NDI to a facility SDI router.

These formats can be transcoded to each other and back again with ease and no noticeable image degradation. For bigger or more diverse workflows, AJA BRIDGE LIVE, with the latest software update, can be bought into the mix to provide additional streaming codecs depending upon the requirements. So, you could be bringing in an HEVC signal from the BRIDGE LIVE, for instance, and with its NDI conversion, then send it to the BRIDGE NDI 3G gateway for distribution and routing purposes. And, even with BRIDGE LIVE you can always convert to SDI if you are trying to get it back into a predominantly SDI facility.

Easy Networked Device Discovery
As another feature of note, BRIDGE NDI 3G allows users to configure the discovery process using a dedicated Source/Destination screen in the interface. For most environments, when first setting up all of the sources and destinations, a fairly heavy discovery process can be run to pull up all of the capable devices on a network so that they can be mapped to SDI channels and/or labeled with custom names (like “Front Of House Camera”) for easy identification.

Once the network is up and running, users can turn off the continual discovery process, or use “names only” to reduce traffic to the NDI library and ensure that they’re getting the required sources and best performance from BRIDGE NDI 3G.

NDI software tools ensure that every device is immediately recognized on the network for the user to work with. There’s no extra discovery using NMOS to deal with (as there is with ST 2110 for example). And the new device is immediately interoperable with other devices on the NDI network. This makes NDI a lot easier to work with and is important for less technical people like those who volunteer at houses of worship.

“When it comes to video over IP, we’ve been watching a range of alternatives emerge and evolve,” said Button, adding that the company has made HDBaseT converters for a while and has recently promoted support for Dante audio networking on an openGear card to embed and dis-embed tracks to SDI. Onboard audio codecs for BRIDGE 3G NDI include NDI (uncompressed float) and SDI (PCM). AJA’s conversion gateway also supports up to 16 channels of audio per each NDI track, as well as SDI. If that’s too much, there is a setting to lower that to 2 or 8. Most software packages handle up to eight channels with no problem.

Addressing A Need For SDI-NDI Conversion
Looking to address the market realities, AJA launched BRIDGE NDI 3G at InfoComm 2021 in Orlando, Florida. The device combines AJA Video’s experience working between both CPU and FPGA processing, that helps with encoding, de-coding, and video transport quality and timing.

“We’ve found a big need for conversions between SDI and IP among systems integrators, so building this product became a real focus for us,” Button said. “We watched as more NDI compatible devices came to market and realized just how vital NDI is becoming for video over IP.”

The more established NDI products available today support from 1-10 GB/s bandwidth, which is easy for everyone from commercial enterprises to colleges and even smaller TV stations to invest in.

“As more of these NDI-compatible products started to emerge—PTZ cameras, switchers, recorders—we quickly saw a missing link in the ability to manage denser workflows,” Button added. “The promise of IP has always been more density available in these simple set ups.”

Preserving Synchronization And Timing
One common issue that BRIDGE NDI 3G solves is synchronization and timing, which are key to success in any SDI and/or hybrid production.

SDI to NDI conversion with the device is straightforward since BRIDGE NDI 3G has complete control over the raster, timing, and frame rate. In most cases SDI sources tend to be homogenized, but BRIDGE NDI 3G can also take different frame rates and raster sizes from SDI and ensure accurate NDI output to the media network.

When it comes to NDI to SDI conversion, BRIDGE NDI 3G could be dealing with many disparate sources from software, hardware encoders, and cameras, plus the results of any badly behaved sources or network interruptions. AJA Video engineering spent a year ensuring a stable SDI output from incoming NDI under various conditions.

As such, BRIDGE NDI 3G supports video processing across scaling, for converting the plethora of NDI rasters to standard SDI rasters; rate, for converting variable NDI sources to standard SDI rates; integer/fractional conversion for ensuring whatever mix of stream rates coming from the NDI network can all be output via either whole or fractional SDI timing; and accommodation of variable delivery of frames via either frame doubling or frame dropping and including audio sample rate conversions to keep everything in sync.

“We spent a lot of R&D time building a robust product with predictable results,” said Button. “We added frame caching, for example, so that when the conversion goes from NDI to SDI, it’s a solid delivery of what the customer is looking for on their SDI infrastructure. It’s similar to frame synchronization in the SDI world.”

High-Density, High-Performance Feature Set

BRIDGE NDI 3G includes dual 10GigE network interface cards. One is handling the NDI media I/O and the other provides flexible control of the box in-facility or over the internet. It also includes a connector for hooking up a preview monitor, but most of the time it’s going to be a set-and-forget situation, or the device can be reconfigured at a central location. Users can then control the box on any web browser from any platform via its built-in web server. The interface is the same regardless of the OS in use.

The gateway device also features high-density SDI connections for up to 16 channels of 3G-SDI I/O up to 60p. This gives users up to four channels of 4K UltraHD, 16-channels of HD, or a mixture of HD and 4K NDI encodes/decodes—all in a compact 1RU form-factor. Using a standard web browser, they can access the interface remotely to view and manage content, including local monitoring preferences. Operators are also able to browse, favorite, label, and filter a large volume of NDI sources on the network, as well as label any SDI inputs or outputs, and see all I/O activity at any given time.

Interoperability And Control
BRIDGE NDI 3G is tested with a huge range of NDI 5 and NDI 4 devices and software to ensure maximum compatibility regardless of the other NDI sources being discovered and utilized. REST API is another option for more fully fledged environments, and BRIDGE NDI 3G also comes with support for IMPI for additional server-oriented tasks.

“We’re confident that we’ve brought an NDI gateway to the market that’s going to address scenarios often associated with NDI such as timing and so forth,” said Button. “We’ve worked hard to synchronize signals correctly, so users get a stable signal coming from their output. Customers get more flexibility, in terms of the amount of devices that support NDI, with ease of implementation as well as less cost.”

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