The Ultimate SRT FAQ

Do you have questions about the Secure Reliable Transport protocol, more commonly known as SRT? You’ve come to the right place! In this ultimate SRT FAQ, we’re answering some of the most frequently asked questions about the video transport protocol that’s changing the way the world streams video.

What is SRT?

In a nutshell, SRT is a video streaming transport protocol and technology stack designed to connect two endpoints for the purposes of delivering low latency video and other media streams across lossy networks such as the public internet. SRT brings the best quality live video over the worst networks. It accounts for packet loss, jitter, and fluctuating bandwidth, maintaining the integrity and quality of your video. With SRT, you can keep your streams secure and easily traverse firewalls.

What does the SRT protocol do?

SRT solves the latency challenges of live video transport that persist despite advances in internet streaming, such as packet loss, jitter, and bandwidth limitations. SRT provides a secure and reliable solution for low latency video transport and includes:

• End-to-end security with AES 128/256 bit encryption
• Packet loss recovery through advanced low latency retransmission techniques
• Video and audio stream timing recovery
• Simplified firewall traversal
• Network health monitoring between endpoints (packet loss, latency, jitter)

For a simple explanation of what SRT does, and how it works, watch our SRT 101 video:

Who developed SRT?

Born from the need to reduce the high cost of contribution by satellite and private networks, SRT was developed and pioneered by Haivision. It was publicly demonstrated for the first time at IBC 2013, and, as the technology progressed, Haivision released SRT as part of its product family and customers started to enjoy the benefits of high-quality, low latency secure video over unreliable public networks.

To encourage widespread adoption so that more companies and customers could benefit from this exciting technology, Haivision released SRT on GitHub in 2017 as an open source technology stack and protocol.

If SRT is open source, does that mean it’s royalty-free?

In a nutshell – yes! As an open source project, SRT source code is freely available for download on GitHub. There are no royalties, long-term contracts or monthly fees. Open source SRT is distributed under the MPL-2.0 license and any third party is free to use the SRT source code and developers can improve upon, use, and re-contribute to SRT.

What is the SRT Alliance?

Co-founded by Haivision and Wowza, the mission of the SRT Alliance is to support the free availability of the open source SRT video transport protocol in order to accelerate innovation through collaborative development. Furthermore, the SRT Alliance promotes industry-wide recognition and adoption of SRT as a common and defacto standard for all low latency internet streaming.

An important goal of the SRT Alliance is to make new features available to the open source community, whether they are submitted for inclusion by community developers, or if they come directly from the Haivision development team. Community-contributed open source SRT functionality is available to any developer, and new developments by SRT Alliance members will migrate back into open source SRT on a regular basis.

Who uses SRT?

Today, SRT is used by thousands of organizations globally in a wide range of industry applications, from IP cameras, video encoders and decoders to gateways, OTT platforms, and CDNs. SRT has also been adopted by leading industry open source technologies including VLC by VideoLAN, GStreamer, Wireshark, FFmpeg, Libav and most recently, OBS Studio. In addition, SRT is being used and endorsed by industry heavyweights across the globe such as Microsoft, Avid, Alibaba, and Tencent to name a few. To read more about how these organizations are harnessing the benefits of SRT, read our SRT Trailblazer posts.

How does SRT keep streams secure?

These days, security is a huge concern for broadcasters and legacy protocols such as RTMP and UDP lack built-in encryption or security mechanisms. SRT resolves this issue by including the industry-standard AES encryption algorithm as an integral part of its software stack. AES is trusted by government organizations in order to keep classified information secure. Financial institutions, major corporations, and even certain military intelligence agencies rely on AES encryption to keep their streams safe.

AES encryption is an important feature that helps to keep SRT streams secure, but it is only one part of a larger security strategy. SRT also ensures that firewall traversal is easy by using a caller/listener handshake concept. This allows for the passage of real-time video streams within secured networks.

Which codecs does SRT support?

All of them! Unlike some other protocols that only support specific video and audio formats, SRT is content-agnostic and does not limit you to a specific container or codec. SRT operates at the network transport level, acting as a wrapper around your content. This means it can transport any type of codec, resolution or frame rate. This is important because it can future proof workflows by working transparently with MPEG-2, H.264, and HEVC for example.

How does SRT compare to RTMP?

We’re glad you asked! This is such a commonly asked question that we wrote a white paper comparing how the two protocols performed when put to the test in real-world conditions. We tested the impact of using RTMP and SRT on round trip, end-to-end latency and, using dedicated hardware encoding and decoding devices, SRT proved to be up to 12 times faster than RTMP. We also tested maximum bandwidth for long-distance streams and, where RTMP failed at long distances at bitrates above 2 Mbps, SRT experienced no issues streaming up to 20 Mbps to any of the global locations tested.

Does SRT work over other networks?

Absolutely! Although SRT was initially developed by our team of IP and video experts to address the main challenges of streaming content over the internet, developers implementing SRT on their own hardware and software stacks, have been demonstrating the protocol’s benefits beyond the public internet.

SRT can be also be used over MPLS, SDN, SD-WAN, cellular and satellite networks. No matter what type of network or application, it’s worth considering SRT for delivering your content. To read more about this, Marc Cymontkowski, Haivision’s resident SRT expert, shares more details on this topic here.

How do I keep updated on the latest SRT news?

We’re always posting about the latest SRT developments here on the Haivision blog, also on Github, the SRT Alliance website, and the SRT Alliance Slack channel.

Ready to get started with SRT?

We recommend you explore our SRT resources page and download the SRT Protocol Technical overview, a comprehensive and detailed guide we put together to help people understand and implement SRT into their workflows.