Video: RIST and Open Broadcast Systems

RIST is a streaming protocol which allows lossy networks such as the internet to be used for critical streaming applications. Called Reliable Internet Stream Transport, it uses ARQ (Automatic Repeat reQuest) retransmission technology to request any data that is lost by the network, creating reliable paths for video contribution.

In this presentation, Kieran Kunhya from Open Broadcast Systems explains why his company has chosen RIST protocol for their software-based encoders and decoders. Their initial solution for news, sports and linear channels contribution over public internet were based on FEC (Forward Error Correction), a technique used for controlling errors in transmission by sending data in a redundant way using error-correcting code. However, FEC couldn’t cope with large burst losses, there was limited interoperability and the implementation was complex. Protecting the stream by sending the same feed over multiple paths and/or sending a delayed version of the stream on the same path, had a heavy bandwidth penalty. This prompted them, instead, to implement an ARQ technique based on RFC 4585 (Extended RTP Profile for Real-time Transport Control Protocol-Based Feedback), which gave them functionality quite similar to the basic RIST functionality.

Key to the discussion, Kieran explains why they decided not to adopt the SRT protocol. As SRT is based file transfer protocol, it’s difficult or impossible to add features like bonding, multi-network and multi-point support which were available in RIST from day one. Moreover, RIST has a large IETF heritage from other industries and is vendor-independent. In Kieran’s opinion, SRT will become a prosumer solution (similar to RTMP, now, for streaming) and RIST will be the professional solution (analogous to MPEG-2 Transport Streams).

Different applications for the RIST protocol are discussed, including 24/7 linear channels for satellite uplink from playout, interactive (two-way) talking heads for news, high bitrate live events and reverse vision lines for monitoring purposes. Also, there is a big potential for using RIST in cloud solutions for live broadcast production workflows. Kieran hopes that more broadcasters will start using spin-up and spin-down cloud workflows, which will help save space and money on infrastructure.

What’s interesting, Open Broadcast Solutions are not currently interested in RIST Main Profile (the main advantages of this profile are support for encryption, authentication and in-band data). Kieran explains that to control devices in remote locations you need some kind of off-the-shelf VPN anyway. These systems provide encryption and NAT port traversal, so the problem is solved at a different layer in the OSI model and this gives customers more control over the type of encryption they want.

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Speaker

Kieran Kunhya Kieran Kunhya
Founder and CEO,
Open Broadcast Systems

Video: RIST in the Cloud

Cloud workflows are starting to become an integral part of broadcasters’ live production. However, the quality of video is often not sufficient for high-end broadcast applications where cloud infrastructure providers such as Google, Oracle or AWS are accessed through the public Internet or leased lines.

A number of protocols based on ARQ (Adaptive Repeat reQuest) retransmission technology have been created (including SRT, Zixi, VideoFlow and RIST) to solve the challenge of moving professional media over the Internet which is fraught with dropped packets and unwanted delays. Protocols such as a SRT and RIST enable broadcast-grade video delivery at a much lower cost than fibre or satellite links.

The RIST (Reliable Internet Streaming Transport) protocol has been created as an open alternative to commercial options such as Zixi. This protocol is a merging of technologies from around the industry built upon current standards in IETF RFCs, providing an open, interoperable and technically robust solution for low-latency live video over unmanaged networks.

In this presentation David Griggs from Amazon Web Services (AWS) talks about how the RIST protocol with cloud technology is transforming broadcast content distribution. He explains that delivery of live content is essential for the broadcasters and they look for a way to deliver this content without using expensive private fibre optics or satellite links. With unmanaged networks you can get content from one side of the world to the other with very little investment in time and infrastructure, but it is only possible with protocols based on ARQ like RIST.

Next, David discusses the major advantages of cloud technology, being dynamic and flexible. Historically dimensioning the entire production environment for peak utilisation was financially challenging. Now it is possible to dimension it for average use, while leveraging cloud resources for peak usage, providing a more elastic cost model. Moreover, the cloud is a good place to innovate and to experiment because the barrier to entry in terms of cost is low. It encourages both customers and vendors to experiment and to be innovative and ultimately build more compelling and better solutions.

David believes that open and interoperable QoS protocols like RIST will be instrumental in building complex distribution networks in the cloud. He hopes that AWS by working together with Net Insight, Zixi and Cobalt Digital can start to build innovative and interoperable cloud solutions for live sports.

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Speaker

David Griggs
Senior Product Manager, Media Services
AWS Elemental

Video: 2019 What did I miss? – Introducing Reliable Internet Streaming Transport

By far the most visited video of 2019 was the Merrick Ackermans’ review of RIST first release. RIST, the Reliable Internet Stream Transport protocol, aims to be an interoperable protocol allowing even lossy networks to be used for mission-critical broadcast contribution. Using RIST can change a bade internet link into a reliable circuit for live programme material, so it’s quite a game changer in terms of cost for links.

An increasing amount of broadcast video is travelling over the public internet which is currently enabled by SRT, Zixi and other protocols. Here, Merrick Ackermans explains the new RIST specification which aims to allow interoperable internet-based video contribution. RIST, which stands for Reliable Internet Stream Transport, ensures reliable transmission of video and other data over lossy networks. This enables broadcast-grade contribution at a much lower cost as well as a number of other benefits.

Many of the protocols which do similar are based on ARQ (Automatic Repeat-reQuest) which, as you can read on wikipedia, allows for recovery of lost data. This is the core functionality needed to bring unreliable or lossy connections into the realm of usable for broadcast contribution. Indeed, RIST is an interesting merging of technologies from around the industry. Many people use Zixi, SRT, and VideoFlow all of which can allow safe contribution of media. Safe meaning it gets to the other end intact and un-corrupted. However, if your encoder only supports Zixi and you use it to deliver to a decoder which only supports SRT, it’s not going to work out. The industry as accepted that these formats should be reconciled into a shared standard. This is RIST.

File-based workflows are mainly based on TCP (Transmission Control Protocol) although, notably, some file transfer service just as Aspera are based on UDP where packet recovery, not unlike RIST, is managed as part of the the protocol. This is unlike web sites where all data is transferred using TCP which sends an acknowledgement for each packet which arrives. Whilst this is great for ensuring files are uncorrupted, it can impact arrival times which can lead to live media being corrupted.

RIST is being created by the VSF – the Video Standards Forum – who were key in introducing VS-03 and VS-04 into the AIMS group on which SMPTE ST 2022-6 was then based. So their move now into a specification for reliable transmission of media over the internet has many anticipating great things. At the point that this talk was given the simple profile has been formed. Whist Merrick gives the details, it’s worth pointing out that this doesn’t include intrinsic encryption. It can, of course, be delivered over a separately encrypted tunnel, but an intrinsic part of SRT is the security that is provided from within the protocol.

Despite Zixi, a proprietary solution, and Haivision’s open source SRT being in competition, they are both part of the VSF working group creating RIST along with VideoFlow. This is because they see the benefit of having a widely accepted, interoperable method of exchanging media data. This can’t be achieved by any single company alone but can benefit all players in the market.

This talk remains true for the simple profile which just aims to recover packets. The main protocol, as opposed to ‘simple’, has since been released and you can hear about it in a separate video here. This protocol adds FEC, encryption and other aspects. Those who are familiar with the basics may whoosh to start there.

Speaker

Merrick Ackermans Merrick Ackermans
Chair,
VSF RIST Activity Group

Video: The next enhancement for RIST

Continuing the look at RIST, the developing protocol which allows for reliable streaming over the internet – even in the event of packet loss, we have a look at a key feature on the roadmap.

The core proposition of RIST is to produce an interoperable protocol which brings the internet into the list of ways to contribute and distribute low-latency video. It’s resilient to packet loss due to it’s ability to re-request packets which have been lost yet is light enough for video streaming. In another talk at IBC, we learn about the latest developments which have added security and many other features to the list of capabilities.

Here, Adi Rozenberg from VideoFlow explains how this will further be extended by upcoming work to allow the source stream to reduce in bitrate in response to reduced capacity in the network. With RIST’s ARQ – the technology which requests missing packets – we find that the retransmissions can actually aggravate bitrate constrictions particularly when they are permanent. Adi proposes the only real way to solve lack of bandwidth issues is to reduce the bitrate of the source.

RIST already includes NULL packet removal so that NULL packets aren’t transmitted and are re-inserted at the remote end. This is usually a great start in reducing the bitrate of the stream. However more is needed, we need a way to tell the encoder to reduce the bandwidth of the video stream itself. This can be accomplished by RTCP.

Adi identifies the problem of identifying when extra bandwidth has returned as a reduction of bandwidth is quickly and easily signalled with retransmissions, but excess bandwidth silently returns. The system gradually increases the encoder bandwidth to always be probing the current balance of bandwidth and bitrate.

This works well when there is a single encoder and a single decoder. When there are multiple decoders, life is more difficult. The solution offered to this is to create a ladder of bitrates all of which are adaptable. Now the destination can switch between profiles. This can be extended to MPTS (Multi-Program Transport Streams) whereby, depending on the destination, services in the MPTS are dropped in order to recover bandwidth. A mechanism is used which prioritises services depending on the destination (i.e. German channels are de-prioritised on delivery to France).

The session ends with a Q&A on stream switching details and use in stat mixing.

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Speakers

Adi Rozenberg Adi Rozenberg
CTO,
VideoFlow