We are often asked about the differences and similarities between the Secure Reliable Transport (SRT) video streaming protocol and the sst protocol protocol and as always, the Haivision team is here to help provide you with the answers. Before we take a deeper dive, let’s start by explaining the fundamentals about what SRT and SST are.
SST and SRT are both real-time video transport protocols designed to transport high-quality and low latency video over unmanaged networks. The fundamental difference between the two is that SRT was initially designed for wired IP networks including the internet whereas SST was developed for streaming over mobile and wireless networks.
What is SRT?
SRT is an open-source video transport protocol used for point-to-point low latency streaming and provides secure and reliable low latency transport of live video over any IP network, even over unpredictable networks such as the public internet. Pioneered and originally developed by Haivision, SRT was awarded an Engineering, Science, and Technology Emmy award in 2018, and is now widely adopted and implemented by hundreds of major television broadcasters and technology vendors.
Its built-in support for AES-128/256 content encryption and low-latency packet loss recovery makes it ideal for remote production and broadcast contribution and, when used over the public internet, is an excellent substitute for dedicated fiber and or satellite. SRT is also a great alternative to the RTMP protocol since it is codec and content agnostic, therefore able to support 4K video and HEVC, and is continually being improved by the open-source community. Designed for interoperability, SRT is also ideal for cloud-based live production workflows requiring low-latency video.
What is SST?
SST is a proprietary and Emmy award-winning network protocol originally developed by Haivision for transporting video over cellular networks. SST aggregates multiple network connections in real-time while dynamically adapting video bitrates to meet bandwidth fluctuations. It also includes content encryption and the retransmission of lost video, audio, and metadata packets.
SST’s unique IP bonding technology can dynamically manage the quality of service to ensure reliable and broadcast-grade video transmission over 3G/4G/5G cellular networks, LAN, Wi-Fi, satellite, and the public internet, making it the optimal choice for live productions that require ultra-low latency video contribution from anywhere such as sporting events like skiing, sailing, cycling, and motorsports.
SST is bidirectional and can simultaneously send a video return stream back to a field unit, establish an IFB and audio intercom between field talent and production staff, and even be used to remotely control IP connected devices such as PTZ cameras via Haivision’s DataBridge technology.
SRT and SST: Answers to Frequently Asked Questions
Can SRT replace SST?
SRT and SST are fundamentally different and complementary video transport protocol technologies. SST is designed for streaming over bonded mobile and other types of networks using Haivision Pro, Air, and Falkon mobile video transmitters as well as the MoJoPro smartphone camera app. SRT was designed to reliably transport live video over the internet at low latency. As an open-source protocol, it can work with any SRT compliant hardware or software. As the two protocols serve different purposes, the two will continue to exist and work side-by-side.
Will SST be included in SRT?
There is no intention to include SST in SRT or to open-source SST. SST is a proprietary technology found in our mobile video transmitters that also supports SRT for interoperability. The two protocols are designed for different use cases, some which may require both technologies. However, many Haivision products including our field units, Haivision StreamHub receivers, and the Haivision Hub 360 cloud solution support both protocols.
Do SST and SRT work together?
Yes! There are lots of use cases where SST and SRT can work together. For example, when covering live sporting events there may be a need for fixed encoders around a venue streaming video with SRT while battery-powered cameras and mobile transmitters capture the action up close and conduct interviews using the SST protocol over a 5G network. Furthermore, our SST receiver, StreamHub, can output video in SRT for downstream interoperability with other broadcast equipment or cloud-based live production platforms. By using both protocols, broadcasters can support a wide variety of video sources and live production workflows.
What’s the benefit of using SST over 5G?
SST enables bidirectional and low latency video transmission over 5G (as well as 3G and 4G), providing a reliable connection between the field and the studio. Although the need for mobile network bonding for bandwidth aggregations may be less with 5G networks, SST can ensure reliability by automatically switching to the most reliable network. SST aggregation of 5G networks can also support high bitrate video such as 4K UHD. The emergence of private 5G networks enables SST to be used in place of cables and RF technology when broadcasting from a fixed venue or even in motion, such as onboard sailboats or automobiles.
The Latest on SRT and SST
We have added SRT protocol support to all our mobile transmitters allowing for interoperability with the complete Haivision product portfolio and other SRT-enabled solutions. SRT is also supported as outputs from the StreamHub mobile video receiver. This allows our mobile video transmitters, or field units, to be used alongside other Haivision broadcast technology including the popular Makito X4 video encoder in a wide variety of broadcast production scenarios, including multi-camera remote production, cloud contribution and distribution, and collaborative decentralized workflows.
Adding the SRT protocol alongside SST dramatically improves interoperability with live broadcast production equipment and remote production workflows that include a mix of fixed and mobile video contribution sources, especially for live sports that require both stationary and portable cameras.
