How RIST Can Help to Make IP Video Broadcast Quality

Transporting video content via the Internet is now a much more viable option than it has ever been before, in part because of better compression technology and infrastructure improvements. However, transporting video at broadcast-grade quality over the Internet is not without difficulties.

While there are a number of transport protocols available for distributing video over unmanaged IP networks such as the Internet, they have their limitations, and interoperability or rather lack thereof is one of the primary issues.

Barriers to adopting IP for transporting video

The key concerns are quality, latency, security and interoperability. Let’s look at each of these in turn.

Ensuring video is delivered in broadcast grade quality can be difficult over IP, in part because Internet bandwidth and connection vary so much. This can be a real challenge when it comes to contribution. In addition, packet delivery is not guaranteed so packets occasionally drop, something that can cause huge issues in a broadcasting environment.

Packet drops can be usually ameliorated by increasing latency.  If the receiver buffers several seconds (or tens of seconds) of content, it can be made more robust to delivery issues, and the transport protocol does not need to be as good.  However, for live operation, high latency is usually not acceptable, making it crucial to use a more advanced protocol which can compensate for loss without a huge increase in latency.

There is a fear among broadcasters that transporting video over the Internet is less secure than traditional closed networks. While many proprietary transport protocols do take security into consideration, RIST goes further making sure that content remains secure throughout the process. End to end authentication is also an important factor for broadcasters when considering security.

Lack of interoperability between the tools that broadcasters and video content providers are using is probably the biggest barrier to IP adoption for transporting content. Put simply, if media company A sends content to media company B and both use different protocols, it is likely that the protocols won’t communicate with each other.

What is Reliable Internet Secure Transport RIST?

Designed by experts to address the challenges of transporting video over IP, RIST is an open specification that can be used for reliable and secure low-latency media delivery. The RIST technical specification defines a base protocol, and this standards based approach is absolutely key because it is the only way to ensure full interoperability, allowing users to pick and mix solutions from different vendors.

The RIST implementation comes from multiple vendors and also supported by an open-source implementation; libRIST. The products that support RIST cover each part of the contribution and distribution workflow, making it easier than ever for broadcasters to transport content over IP.

RIST profiles in brief

RIST is divided into profiles, each of which is an open and collaboratively developed protocol specification. RIST profiles include simple, main and advanced, and while each profile incorporates an additional layer of features and functionality, even the simplest profile ensures video can be sent over IP without compromising on quality. Figure 1 shows the released RIST profiles and their main features.

Figure 1: RIST Profiles

RIST Simple Profile: published as VSF TR-06-1

This is the “core” of RIST, implementing low-latency packet recovery, as well as multi‑link support.  The Simple Profile is ideal for video transport applications over the Internet where security is not needed

The basic packet format for RIST Simple Profile is RTP, defined in RFC 3550.  This allows for basic stream interoperability with legacy broadcast systems over IP.  Lost packet recovery is through the well-known Automatic Repeat reQuest (ARQ) technique. Simple Profile supports operation over multiple links, in two modes: seamless redundancy, which sends full copies of the stream using two or more links; and bonding, in which the stream is split over two or more links, which essentially combines their capacities. 

RIST Main Profile: published as VSF TR-06-2

Main Profile adds security (both encryption and authentication) to Simple Profile, as well as support for in-band data. It is intended for applications where security is needed. Users can select the preferred option for encryption and security depending on requirements.

One of main features of Main Profile is tunneling support.  Tunneling is used to simplify network configuration and to support in-band non-RIST traffic. Main Profile also includes the following additional features: null packet suppression and high bitrate operation.

RIST Advanced Profile: published as VSF TR-06-3:2021

The main feature of RIST Advanced Profile is tunnel-level ARQ, allowing RIST to become a transport for other protocols. Using RIST, a reliable tunnel can be created between two endpoints, and any IP or Ethernet-based protocol can be reliably carried over this tunnel. Other features of the Advanced Profile include transparent fragmentation support, to support larger datagrams, with fragment-level ARQ and optional support for lossless data compression, using the LZ4 algorithm. 

Products supporting RIST continues to grow

RIST is available in a continuously expanding range of commercial products throughout the media distribution lifecycle, enabling live video to be encoded, processed, and distributed over IP. 

For encoding and decoding of video for quick delivery and playback of live content, RIST compatible solutions are available from providers such as Ateme, Cobalt, DTVI, Evertz, Open Broadcast Systems, QVidium, Sencore, SipRadius and Vitec.

Video processing and conversion tools that support RIST are also available. Cerberus Tech's IO easily converts IP video traffic to the right protocol depending on available equipment and requirements. A number of tools for automated video QC and for capture, control, conversion, and output using RIST are available from Drastic Tech. Companies such as Cobalt, Evertz, Sencore, and VideoFlow provide digital media gateway tools.

At the point of contribution or distribution, the following providers have solutions that can enable delivery using RIST: Amazon Web Services, Cerberus Tech, Easy Tools,  Evertz, Intinor, M2A Media, Net Insight, and Zixi.

RIST: making it easier to send broadcast grade video over IP 

The RIST protocol has been designed by industry experts to address the requirements of the broadcast industry, and it is continually being refined and updated as those needs change. The standard has been developed with multi-vendor cooperation at its core.

The resulting protocol is open specification and can be freely downloaded from the VSF web site. It can be easily implemented by any vendor because of the lack of restrictions and royalties, and this is helping to ensure that it is implemented in a wide range of products. Products that include RIST support will all work together, so broadcasters can choose the products that best suit their needs, without the worry of products not being interoperable.

RIST clearly has a role in ensuring that high quality video can be contributed and distributed efficiently and securely over IP, and this role will become more important as the broadcast industry continues to shift towards IP based workflows.