In the late 2000s, many equipment vendors began coming up with new ways to distribute content over the Internet, as a cost advantage over traditional satellite and fiber infrastructures. The concern was that these new solutions were proprietary and did not interoperate, even though they were all broadly equivalent.

Enter the Video Services Forum (VSF), which in 2018 demonstrated at that year’s IBC convention an open specification protocol called the Reliable Internet Streaming Transport (RIST) that aimed to solve the IP issues of dropped packets and latency and allow it to be used for professional grade contribution - at about a  lower cost than conventional content delivery methods.

“In 2017, a major sports network came to the VSF and asked them to come up with an interoperable solution for contribution over the Internet,” said Dr. Ciro Noronha, President of The RIST Forum. Noronha also serves as CTO of Cobalt Digital, where they make encoders and other products that are fully compatible with RIST. “We [the RIST Activity Group within VSF] came up with an open specification that you can download for free. This way everything's free and you are not locked to a proprietary vendor solution. An open source implementation of RIST is also available for free.”

Since that time the RIST Activity Group has continued to improve upon the spec, adding new features to ensure its value to distribute even the most high-profile live events. One feature enables the user to recover dropped packets as they happen using a redundant path approach.

“With RIST, if you have a good network connection, you can adjust the latency requirements,” said Dr. Noronha. “Using redundant paths, the receiver gets two copies of every packet, and throws one away. Moreover, it only needs to request retransmission of packets that are lost on both links.”

However, if one link goes down completely, the user is still receiving the content from the other one, and there are no glitches. That’s called “seamless redundancy”, which is a feature that has existed in SMPTE for uncompressed video feeds.

Dr. Noronha cited a test done with RIST-compliant encoders and decoders from Open Broadcast System, based in the UK, which demonstrated a reliable link between London and New York that was up for nine months with two ISPs. Both of them went down at different times, yet the link didn't have a single uncorrected packet loss.

The RIST Forum recently announced two new features for the protocol, Decoder Synchronization and Multicast Discovery. These follow three other ones that were released since 2020. The first step was to detail the RIST Simple Profile, which came out in 2018 and is identified as TR--06-1. Basically, it defines the basic ARQ (Automatic Repeat Query) technology used to recover lost packets. This spec was updated in 2020 to include an optional "RTT Echo" message that streamlines the process of configuring packet buffers.

Next came TR-06-2, which addresses encryption and authentication security. This has two methods of encryption to protect content in flight and authentication to make sure that the content is accessible to the right person.

In 2021 TR-06-3 was released, which provides a protected tunnelling mode that can carry any legacy protocol, including RTP-based media signals such as SMPTE ST 2110, ST 2022 and MPEG TS over UDP. In addition, bidirectional protocols based on TCP can be transported securely and reliably in the same packet tunnel while consuming only a single UDP port to simplify firewall configuration.

[It was revised in 2022 to include a reference to the EAP SHA256-SRP6a Authentication Protocol, which is documented in Annex D of TR-06-2:2022.]

Among the newest ancillary features, detailed in TR-06-4, part 4, the Decoder Synchronization provides a way to synchronize the decoder playback when multiple encoders are transmitting signals to multiple decoders over IP for applications such as live sport or worship.

When multiple cameras are in use at live events or for worship in remote locations, their feeds need to be played back in a synchronized fashion. TR-06-4 Part 4 provides a common specification to achieve this, supporting an arbitrary number of encoders and decoders.

The fifth ancillary feature detailed in TR-06-4 Part 5, Multicast Discovery, provides a simplified way to manage multicast traffic over RIST tunnels, to avoid unnecessarily sending streams to receivers not interested in them, thus saving bandwidth.

Dr. Noronha said that more features are coming later this year or early in 2025, including those for Unified Control (possibly working with the AMWA initiative).

“If you want these things to scale, you need to have a master control or centralized control system that makes the connection and manages everything,” he said today this is done manually. “What you are going to see later in the year is the hybrid satellite part. I don't think you're going to see control this year because it is not an easy problem.

Technical recommendations are freely available from the VSF website for all to download and use.

Thus the momentum surrounding RIST continues and it has now emerged as a major part of the content distribution landscape, with 300 companies now supporting this open, interoperable, and technically robust solution for low-latency live video over unmanaged networks. It’s allowing more people to get involved with contribution and distribution at a much more affordable level.

Dr. Noronha said developmental work within the VSF on RIST is basically done, as a useful specification, but a few minor tweaks are still possible into the future to keep it viable for whatever new technology comes along to improve performance.

“[The RIST Forum members] used to meet a lot more often but most of the big problems are solved now, so there’s less to do,” said Dr. Noronha. “After so many years working on it, it’s a good feeling to bring what we originally promised to the industry for the good of everyone.”