It seems that network protocols are a lot like potato chips. You can’t have just one. Here’s what you need to know about the latest transport protocol and why everyone is talking about RIST for live streaming and moving media across the public internet. 

If you’ve been following protocols for a while, you know that UDP multicasting is a simple message-oriented protocol used to transport audio and control data at very low latency. We can reduce WheatNet IP audio packet timing to ¼ ms for minimum latency in part because of UDP multicasting, which means that local studio controls and audio transport are almost instantaneous.

But what happens when we go beyond the studio network and want to live-stream audio and control data in real-time across the public network, where links are less reliable and distance adds more delay?

Enter RIST, or Reliable Internet Stream Transport, which adds error correction and packet recovery to UDP multicasting. RIST uses things like RTP sequencing to identify potential packet losses and multi-link bonding to guarantee media delivery over these public links with very little delay and often without having to compress or reduce the bits, and hence the quality of audio being transported. Based on established protocols widely adopted by the broadcast industry, including RTP and SMPTE-2022, RIST is interoperable with broadcast-grade equipment, including Wheatstone products and those of its partners. It is a relatively new arrival in the media transport world and it’s especially timely given the growing number of high-speed links that are now making it possible to stream at full audio bandwidth.

Or, as our senior streaming software engineer Rick Bidlack explained, “We have all this available bandwidth on public networks for getting the full audio bandwidth up to the cloud or wherever we want it. RIST just makes sure that it arrives there.”

Now part of our I/O Blade 4s, streaming appliances Wheatstream/Streamblade, and streaming software (Layers Stream), RIST provides WheatNet IP audio studios both the speed and reliability needed to take advantage of high-speed broadband public networks for live streaming, news feeds or sports contributions across distances. You can now stream audio from your WheatNet IP audio studio over a public high-speed link to a regional server or cloud data center at full audio bandwidth and 24-bit resolution without noticeable latency, depending on distance.

Opening up a RIST stream session from your Wheatstone AoIP streaming appliance or software creates a dedicated channel between a local IP address and an IP address on the far end and establishes a low-latency, high-quality connection between the two points. And because RIST interoperates with RTP/UDP at the transport layer, it integrates easily into WheatNet IP audio networked studios. For example, our Layers Stream software running in a data center can receive a stream via RIST as well as send a stream via RIST back to a Blade 4 in your studio to be routed, processed, and controlled locally through the WheatNet IP audio network.

RIST is fast becoming an important protocol for the next evolution in AoIP.

Our Jeff Keith reflects on the current state of AM, AM processing, and sports.

“Sports is generally a high energy activity for both players and audience, so hearing it on AM, and processed 'hard' as most AM's do, adds even more energy to the listening experience…AM audio is typically processed much more aggressively than FM, and increasing the average modulation density not only increases AM service area coverage but also adds 'urgency' to the audio. That same feeling of urgency created by aggressive audio processing can also add a bit of 'authority' to the audio.”

Jeff Keith, CPBE, NCE
Senior Product Development Engineer,
Audio Processing Development

Shown, Jeff Keith in his audio processing lab where sound ideas are modeled and tested for AM, FM, streaming and mic processing. (Note our new Lion FM audio processor and Voice 1 processor on the bench to the left). 

You might recall the WheatNet IP audio network “alarm clock” we told you about a while back. CE Greg Manfroi (WUIS-FM, Springfield, Illinois) created a simple script for an old dial-up remote-control switch that he used to alert the news staff when the morning guy hit the snooze button one too many times. 

It was one of our early examples of scripting, and since then, we’ve added many ingenious ways scripting can be used to increase AoIP network usability.

So, how easy is it to add a few software routines to your WheatNet IP audio network?

In many cases, by using our wizard GUIs you can go from not knowing much about networking to writing basic scripts for your AoIP system.

These GUIs are basic scripting programs we’ve developed over time that you can use and customize for your own purposes. Examples of use include setting up a temporary intercom button between a producer and announcer and programming a button to fire off a relay to interrupt on-air program temporarily for an EAS alert.

Scripting Wizards

Scripting wizards are available for programming buttons on our SS-8 control panels, TS-22 talent stations and certain consoles and control surfaces (Sideboard, LXE, GSX, and Tekton, or any console surface that you add a scriptable control panel to; we have scriptable OLED control modules for a variety of control surfaces).

Scripting wizards can be used for controlling a surface remotely from a panel, for turning a fader channel on or off, for firing presets on audio processors, for sending automation commands, and for a wide variety of other purposes. Often it can be as easy to set up as navigating a checklist of basic choices for types of salvos, destinations, and sources.

For a little more customization, you can cut and paste an existing script into a work area and make modifications. For example, one CE was able to use an existing script to turn the virtual utility mixers in the WheatNet IP audio Blades on or off from a control panel. But he needed a few more lines of code for audio ducking during a mid-show break in the live satellite feed, which cut away abruptly to silence and then came back on again – at full volume – following the station ID.

He modified the script slightly so that when his automation system gets the satellite closure, the WheatNet IP ducks the feed for a voice track. Thanks to a few scripted lines of code, he was able to solve that problem easily – as well as another recurring problem: the same engineer modified a script to do the studio equivalent of the two-man rule as a foolproof way for volunteer hosts to switch between studios. As a result, it takes a combination of two button presses to activate the salvo for the studio switch rather than just one button that an announcer might accidentally press, inadvertently taking the station off the air.

To get started on scripting, check out our Scripters Forum. You’ll find documents, starter scripts, and a whole knowledge base available to you for adding scripts to your WheatNet IP audio network.