The streaming industry is on an ever-evolving quest to reduce latency to bring it in line with, or beat linear broadcasts and to allow business models such as gaming to flourish. When streaming started, latency of a minute or more was not uncommon and whilst there are some simple ways to improve that, getting down to the latency of digital TV, approximately 5 seconds, is not without challenges. Whilst the target of 5 seconds works for many use cases, it’s still not enough for auctions, gambling or ‘gamification’ which need sub-second latency.
In this panel, Jason Thielbaut explores how to reduce latency with Casey Charvet from Gigcasters, Rob Roskin from CenturyLink and Haivision VP Engineering, Marc Cymontkowski. This wide-ranging discussion covers CDN caching, QUIC and HTTP/3, encoder settings, segmented Vs. non-segmented streaming, ingest and distribution protocols.
Key to the discussion is differentiating the ingest protocol from the distribution protocol. Often, just getting the content into the cloud quickly is enough to bring the latency into the customer’s budget. Marc from Haivision explains how SRT achieves low-latency contribution. SRT allows unreliable networks like the Internet to be used for reliable, encrypted video contribution. Created by Haivision and now an Open Source technology with an IETF draft spec, the alliance of SRT users continues to grow as the technology continues to develop and add features. SRT is a ‘re-request’ technology meaning it achieves its reliability by re-requesting from the encoder any data it missed. This is in contrast to TCP/IP which acknowledges every single packet of data and is sent missing data when acknowledgements aren’t received. Doing it the SRT, way really makes the protocol much more efficient and able to cope with real-time media. SRT can also encrypt all traffic which, when sending over the internet, is extremely important even if you’re not sending live-sports. In this video, Marc makes the point that SRT also recovers the timing of the stream so that the data comes out the SRT pipe in the same ‘shape’ as it went in. Particularly with VBR encoding, your decoder needs to receive the same peaks and troughs as the encoder created to save it having to buffer the input as much. All this included, SRT manages to deliver a transport latency of around 2.5 times the round trip time.
Haivision are members of RIST which is a similar technology to SRT. Marc explains that RIST is approaching the problem from a standards perspective; taking IETF RFCs and applying them to RTP. SRT took a more pragmatic way forward by creating a binary which implemented the features and by making this open source for interoperability.
The video finishes with a Q&A covering HTTP Header compression, recommended size of HLS chunks, peer-to-peer streaming and latency requirements for VoD.
SRT allows unreliable networks like the Internet to be used for reliable, encrypted video contribution. Created by Haivision and now an Open Source technology, the alliance of SRT users continues to grow as the technology continues to develop and add features. This panel, from IBC 2019, is an update on what’s new with SRT and how it’s being used daily in broadcast.
Marc Cymontowski starts with an overview of the new features of SRT, mentioning its active Github repository, pointing to recent advances in the encryption available, upcoming FEC and the beginnings of SMPTE ST 2022-7 like redundancy. He also takes a look at how SRT fares against RTMP, the venerable incumbent technology for contribution of streams over the internet. Official support for RTMP will be coming to an end next year, so there is much interest in what may replace it. Marc makes the case that for the same link, SRT tends to have a latency of a half to a third and also performs better at higher bitrates.
RTP, the Real-Time Transport Protocol, is an important feature when it comes to redundancy. By using RTP’s ability to stamp each packet, the receiver can take two identical RTP streams – say from two separate ISPs and fill in missing packets on one stream from the packets of the other stream. This is a very powerful way of ensuring reliability over the internet so Marc makes the point that using SRT doesn’t stop you using RTP.
Simen Frostad then takes to the stage to explain why Bridge Technologies has added SRT support and how the SRT Hub will be a very important step forward. Then it’s Leonardo Chaves’ turn who explains how broadcaster Globo is using SRT to transform its video workflows and reduce OPEX costs to one third satellite costs.
Steve Russell from Red Bee talks about how they use SRT to create new, or lower cost, circuits and services to their customers. They’re able to use the internet not only for contribution from events but also to safely get video in and out of the cloud.
With these use-cases in mind, the panel opens up to thirty minutes of wide-ranging technical and non-technical questions.
Real-life use cases on this innovative Open Source technology from the SRT Alliance recorded at IBC 2018.
SRT, Secure Reliable Transport, is an open source video transport protocol and technology stack that optimises streaming performance across unpredictable networks with secure streams and easy firewall traversal, bringing the best quality live video over the worst networks.
The SRT Open Source project, driven by the SRT Alliance, is a collaborative community of industry leaders and developers striving to achieve lower latency internet video transport by continuously improving open-source SRT.
At the end of the day, a technology is only as good as what it can actually do rather than what people promise and, in this talk, there are only real-world case studies from major companies. Including some brief words from Microsoft Azure’s Satish Annapureddy discussing Microsoft’s recent membership of the SRT alliance.
Glenn Goldstein, Chief Technology Convergence Officer, Viacom Marc Cymontkowski, Senior Director, Core Technology, Haivision Tony Jones, Principal Technologist, MediaKind Miljenko Logozar, Director of Technology Solutions & Integrations, Al Jazeera Chris Smith, Development Executive, News Technology, Sky News
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