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Video: RIST in the Cloud

Posted on 22nd April 2020 by Adam K

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: RIST Pre-Shared Key Encryption

Posted on 14th February 2020 by Russell Trafford-Jones

An important factor when sending production video feeds and other media over the internet for most people is encryption. When distributing to the end user, it’s different, but for contribution having the assurance that no-one else can view the video is very reassuring to all parties even when the content doesn’t necessitate it. RIST has been in development for a while and has grown beyond the simple profile which only dealt with packet loss. Now with the main profile, encryption is possible; there are actually two ways to encrypt. One uses DTLS which is the UDP-based equivalent of the same TLS encryption that https:// websites use, the other uses pre-shared keys (PSK).

Sergio Ammirata from DVEO starts the talk by introducing the main profile and the use of GRE tunnels. The use of a tunnel from sender to receiver allows for a single connection to carry multiple channels of multiplexed data. Importantly. it also allows the encryption to happen to the tunnel rather than to each media stream separately.

The next section of the talk revises what DTLS is: part of the main profile providing TLS encryption to UDP. Given this is an encryption method, it’s important to realise it is not part of the data-loss recovery algorithms. Since DTLS is based on TLS, it will also need certificates. Just like websites you have the choice of having a self-signed certificate or one signed by a trusted authority. This means that you not only know that you are sending encrypted data, you are also sending it to a trusted computer, not someone unintended. Sergio takes us through the workflow of verifying the certificates highlighting, for instance, the requirement for a realtime clock otherwise the start and expiry dates in the certificates wouldn’t have any meaning.

With PSK, there is no authentication. It encrypts the whole of the GRE tunnel except for headers with an AES key related to the pre-shared passphrase. The encryption is changed periodically by an automatic process. It’s important to realise that because this is so deterministic, this can be used for bonded connections. When Sergio then looks at the data flow for using PSK, we see that that it is much simpler with many fewer handshakes.

As to when PSK is the route to take over using DTLS, one-to-many transmission is an obvious candidate but also where there is only one-way communication such as most satellite links. Sergio finishes the talk by looking at the use of FEC and taking questions from the floor.

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Speaker

Sergio Ammirata
CTO,
DVEO

Video: The next enhancement for RIST

Posted on 19th December 2019 by Russell Trafford-Jones

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
CTO,
VideoFlow

Video: RIST Main Profile Description

Posted on 5th December 2019 by Russell Trafford-Jones

RIST solves a problem by transforming unmanaged networks into reliable paths for video contribution in an interoperable way. RIST not only improves reliability through re-requesting missing packets, but also comes with a range of features and tools, not least of which is tunnelling. Cobalt Digital’s EVP of engineering, Ciro Noronha explains how the protocol works and what’s next on the roadmap.

Ciro starts with a look at the RIST Simple Profile covering the ARQ negative acknowledgement (NACK) mechanism, link bonding and seamless switching. He then moves on to examine the missing features such as content encryption, authentication, simpler firewall configurations, in-band control, high bitrates, NULL packet extraction. These features define RIST’s Main Profile.

Tunnelling and Multiplexing is a technique to combine Simple Profile flows into a bi-directional tunnel, providing simpler network and encryption configuration. Using a GRE (RFC 8086) tunnel, RIST provides a full, protocol agnostic tunnel and a UDP-only reduced overheard mode which only requires 0.6% data overhead to implement. Ciro explains a number of setups, including one where the connection is initiated by the receiver – something that the Simple Profile doesn’t allow.

Authentication and Encryption are covered next. DTLS us the UDP implementation of TLS which is the security mechanism used on secure websites. This provides security to the tunnel so everything which travels through is covered. Ciro explains the pre-shared key (PSK) mechanism in the Main Profile.

The talk finishes by covering NULL Packet removal, also known as ‘bandwidth optimisation’, header extension which extends RTP’s sequence number to allow for more in-flight packets and questions from the audience.

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Speaker