FREQUENTLY ASKED QUESTIONS
For more information about the SRT Alliance and the SRT technology, have a look at our frequently asked questions and answers.
SRT, which stands for Secure Reliable Transport, is a video streaming transport protocol and technology stack (similar in concept to Reliable UDP). The open source implementation of SRT is based on Haivision’s SRT, a technology package and protocol that connects two endpoints for the purposes of delivering low latency video and other media streams across lossy networks.
SRT key features:
- AES 128/256 bit encryption
- Packet loss recovery through advanced low latency retransmission techniques
- Video and audio stream timing recovery
- Ability to designate any endpoint as “sender”, “receiver”, or “rendezvous” mode
- Detect the network performance between endpoints (packet loss, latency, jitter)
Despite advances in internet streaming, live video transport still faces latency challenges due to:
- Packet loss when sending UDP-based low latency MPEG Transport Streams over the public internet
- Bandwidth limitations introduced by network congestion control when using the TCP protocol in RTMP
- Segment-based protocols such as HLS and DASH transmitted over HTTP (TCP)
Generally, overcoming these problems requires the provisioning of high-cost reserved links like MPLS or satellite networks. With the open source implementation of SRT, any developer has access to a streaming protocol that provides a secure and reliable solution for low latency video transport with packet loss recovery, end-to-end security with AES encryption, network health monitoring between endpoints, and simplified firewall traversal. Furthermore, developers can enable SRT functionality over any network, including cost-effective public internet.
SRT is a video streaming technology that leverages a combination of broad video ecosystem components and technology advantages to enable the best quality live video over unpredictable networks, even the public internet. SRT accounts for packet loss, jitter, and fluctuating bandwidth, maintaining the integrity and quality of your video. SRT enables you to keep your streams secure and easily traverse firewalls.
SRT source code, complete with building tools and tutorials, is for any developer who aims to deliver low-latency video streaming solutions for their users. This can include broadcast solution providers, video streaming technology vendors, enterprise video platform developers, live event production companies, OEM hardware developers, and any other developer needing low latency video streaming for hardware or software. Sample utilities are also included in the repository to accelerate trials and provide integration code examples.
Open source SRT will be distributed under LGPLv2. We chose LGPL because it strikes a balance between driving adoption for open source SRT, while encouraging contributions to improve upon it by the community of adopters. Thus, any third party is free to use SRT as a self-contained library dynamically linked at runtime. Should they make source code changes, they would be obligated to make those changes available to the community.
Any third party who wishes to statically link with the SRT library or make changes to the source code and does not wish to share those changes, the party must apply for a license from the LGPLv2 license holders.
Contributors from the open source community own it. The open source community reaps all the benefits of source code contributions; however, copyright and ownership remain with their respective contributors. The contributors grant licenses to others to use under LGPLv2 license. The open source implementation of SRT is managed and maintained by the SRT Alliance.
Haivision is providing SRT to the world to show market leadership and to embrace open source collaboration for progressing the technology.
For over 13 years, Haivision has been dedicated to innovating in video streaming technology. As video streaming becomes ubiquitous, Haivision recognises the need to ensure broader ecosystem collaboration given that real world custom workflows inevitably combine technology from multiple vendors. In order to ensure seamless interoperability in these complex ecosystems, Haivision believes that SRT can serve as the low-latency glue that bonds video streaming technology together. Wowza shares this vision with Haivision.
Haivision recognizes that no matter how great SRT is, adoption is unlikely if the technology is proprietary. Technology providers need reassurance that they have control of their own technology roadmaps. Thus, the open source initiative.
By opening up SRT technology to the world, everybody including Haivision customers can benefit from an open ecosystem where they will be able to integrate their video streaming technologies with other video solutions, network infrastructures and systems.
Wowza is co-sponsoring and supporting the SRT open source initiative to promote the adoption of SRT by incorporating the technology within its offerings, starting with Wowza Streaming Engine™, to receive and deliver low latency, high availability streaming solutions. Wowza recognizes delivery of streaming video with low end-to-end latency faces a variety of challenges, the most difficult being able to deliver at scale while maintaining high interactivity.
As a leader in the streaming industry, Wowza is committed to advancing the open source use of SRT technology. Wowza seeks to collaborate with customers, industry leaders, and alliance members to make future advancements built on SRT available within the open source framework.
As an open source project, SRT source code is available for download and use by any developer. Should these developers want to promote the use of SRT in their applications, they can self certify and refer to themselves as “SRT Ready”. Partners will be responsible for providing their own testlab, installation documentation, plans, and results. The SRT Ready logo is available upon request from email@example.com.
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 will promote 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 submitted for inclusion by community developers, or coming directly from Haivision or Wowza development teams. Community-contributed open source SRT functionality will be available to any developer, and new developments by SRT Alliance members will migrate back into open source SRT on a regular basis.
SRT is now available on several solutions by many manufacturers and service providers. SRT can be found on various encoders, decoders, gateways, players, streaming platforms and more, including VLC and GStreamer. To know who offers SRT Ready solutions, visit the Members page and select the SRT Ready filter.