SRT (Secure Reliable Transport) Protocol

High-quality professional media transport over the Internet is maturing rapidly, creating the need for open ecosystems in which multiple vendors can interoperate. Secure Reliable Transport (SRT) is a free open source video transport protocol and technology stack that is available for anyone to use. It is endorsed and implemented by many vendors in the industry.

Similar forces are now at work across the media broadcast industry as satellite and cable is joined by internet protocol (IP) as a form of media transport. Internet distribution, which is also known as over the top (OTT), is on course to be the dominant form of media broadcast worldwide. At the same time, IP is replacing SDI within the facility and for the contribution of media to the production hub.

The need for greater agility to support ultra-high resolution video, better connectivity of infrastructure, and growing OTT demand is driving this evolution at pace. For the first time, the production and the distribution of broadcast programming will rely on the same underlying (IP-based) technology.

SRT transport

While RTMP remains the most common protocol for video contribution, the technology wasn’t designed for interactivity. In terms of end-to-end latency and video quality, SRT transport outperforms RTMP as detailed in Haivision’s white paper RTMP vs. SRT: Comparing Latency and Maximum Bandwidth | Haivision.

According to consultants Deloitte, “Legacy protocols such as RTMP, developed over a decade ago to encode video and move it across networks to clients, will likely be displaced by newer solutions such as SRT, designed to further decrease latency and meet the demands of live and on-demand streaming.”

https://www2.deloitte.com/content/dam/insights/us/articles/722835_tmt-predictions-2020/DI_TMT-Prediction-2020.pdf

Specifically, SRT transport is designed to manage and solve:

  • Packet loss (packets that the router discards)
  • Jitter (packets that arrive at the wrong time)
  • Latency (delay between when the video is captured and when it plays on viewers’ devices)
  • Changes in bandwidth (fluctuations in the capacity between two points)

In this way, SRT enables a layer of error correction that reduces the need for expensive network infrastructure.

UDP and TCP are both core components of the internet protocol suite, residing in the transport layer. SRT takes some of the best aspects of User Datagram Protocol (UDP), such as low latency, but adds error-checking to match the reliability of Transmission Control Protocol/Internet Protocol (TCP/IP). While TCP/IP handles all data profiles and is optimal for its job, SRT can address high-performance video specifically. By combining the speed of UDP and the reliability of TCP, SRT provides the following benefits.

SRT networking benefits

The benefits of SRT as claimed by the SRT Alliance, include:

  • High quality: Provides professional, high-grade video across any network — withstanding up to 10% packet loss without detectable degradation.
  • Resilient: Maintains stream integrity by accounting for packet loss, jitter, and fluctuating bandwidth.
  • Cost-effective: Replaces expensive satellite networks or rigid MPLS networks with affordable and flexible public internet.
  • Interactive: This allows you to deliver two-way, interactive video from anywhere.
  • Low latency: Enables near real-time IP communications as fast as UDP with the reliability of TCP.
  • Media-agnostic: Acts as a wrapper around your content — whether MPEG-2, H.264 or HEVC.
  • Firewall friendly: Reliably streams from unknown locations and event centers without requiring additional IT resources.
  • Secure: End-to-end 128/256 bit AES encryption makes sure your content is protected from contribution to distribution

One notable limitation of SRT is that it’s not as widely supported for playback as technologies like HTTP Live Streaming (HLS). For that reason, most SRT-based workflows leverage a streaming server or service to repackage content.

The SRT Alliance

The SRT Alliance of supporting vendors was created in 2017 to promote the industry-wide recognition and adoption of SRT as a common standard for all low-latency internet streaming.

Haivision subsequently released SRT on GitHub to encourage interoperability, as well as a comprehensive technical review that serves as the specification. This makes it simple to verify connectivity without costly hardware or software solutions.

Microsoft announced support for the protocol in 2019, making SRT an ingest option alongside RTMP.

Since then, Haivision has launched SRTHub a cloud-based service for routing media across the Microsoft Azure backbone.

Net Insight is a member of the SRT Alliance. Joining the SRT Alliance is in line with Net Insight’s strategy to embrace open technology for transporting professional high-quality media content over the Internet.

SRT Open Source

The SRT Open Source project, managed and maintained 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.

Open source SRT is distributed under the MPL-2.0 license. Haivision chose Mozilla Public License because it strikes a balance between driving adoption for open source SRT while encouraging contributions to improve upon it by the community of adopters.

Any third party is free to use the SRT source in a larger work regardless of how that larger work is compiled. Should a third party make source code changes, they would be obliged to make those changes available to the community.

Open source is designed to deliver interoperability and longevity with large-scale adoption.

CASE STUDIES

World’s largest Nimbra networks to HD

EBU has selected Nimbra platform for the Eurovision fiber network

The European Broadcasting Union (EBU)

World’s largest alliance of public service media organisation

Since 2004, when the EBU selected Net Insight’s Nimbra platform, the EUROVISION Fibre Network (FiNE) has evolved with Net Insight’s latest products and features.

The EUROVISION satellite and fibre network is one of the largest and most rock solid in the world. It delivers more than 80,000 hours of programming every year, the majority of which is live sports. Its undisputed reputation for flexibility and reliability is reflected in the prestigious events it regularly carries on the EUROVISION network.

“We continue our solid relationship with Net Insight for the development of our network since we aim to be the standardbearer for QoS and reliability around the world.”

Related resources

WHITE PAPER

Cloud Ingest of Live Video

As cloud production becomes an integral part of broadcasters’ live workflows, the corresponding cloud infrastructure becomes an integral part of the media transport network.

BLOG

Open Insight #2

Welcome to the second edition of Open Insight, where I will share thoughts and updates with our shareholders, other stakeholders and anyone with a general interest in the company.

FAQ

What SRT means?

Secure Reliable Transport is a video streaming transport protocol and technology stack.

What is SRT transport used for?

The open source implementation of SRT connects two endpoints for the purposes of delivering low latency video and other media streams across lossy networks.

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