What is SRT Protocol? Why is it the Future of Streaming?4 min read

December 9, 2020 4 min read
What is SRT protocol

What is SRT Protocol? Why is it the Future of Streaming?4 min read

Reading Time: 4 minutes

Originally created by Haivision and made public in 2017, SRT is considered the new protocol for video streaming by many industry experts. What is SRT exactly? Do you need this technology to livestream? And how broadcasters can benefit from it? Explore everything below.

What is SRT?

Secure Reliable Transport (SRT) is an open-source data transport protocol. SRT utilizes the User Datagram Protocol (UDP) — one of the core layers of the internet protocol suite in computer networking. This technology was originally created by Haivision and has been promoted by the SRT Alliance.

Because SRT enables the secure and reliable transport of data across unpredictable networks — like the internet, this protocol is optimal for audio and video streaming.

SRT promotes the delivery of high-quality, and low-latency media data. And by optimizing the streaming performance with reliable streams and firewall traversal, it is proven to produce top-tier quality live videos, even over the poorest network connectivity.

This powerful technology has been an ideal choice for leading industry companies such as the NFL and Fox News. Many major open-source technologies like VLC by VideoLan, OBS Studio, Wireshare, FFMpeg, GStreamer and Libav also apply this transmission protocol.

SRT enables the secure and reliable transport of data across unpredictable networks — like the internet, making this protocol a preference for audio and video streaming.

Applications of SRT

You may find the application of SRT in an end-to-end video stream workflow, from contribution to distribution.

Thousands of organizations across the world from a broad range of industries have adopted this technology. The application of this protocol is also diverse, from livestreaming, multistreaming, video encoding, gateways, IP cameras, over-the-top (OTT) platforms, to content delivery networks (CDN).

On the technical side, it provides reliable transmission similar to the Transmission Control Protocol (TCP). However, while TCP delivers at the transport layer, SRT supports at the application layer, using the UDP protocol as an underlying transport layer. SRT also supports packet recovery in low latency (120 milliseconds by default) and encryption using the Advanced Encryption Standard (AES).

In short, with SRT, end-to-end streaming security, video resiliency, and dynamic endpoint adjustments in real time based on network conditions are possible.

Benefits of SRT

As mentioned before, the biggest benefit of streaming with SRT is the high-quality video delivery on any network. This protocol dynamically adapts itself to any network connections that could appear between the beginning and end of the transmission in real-time. What this means is that this process can greatly reduce the effects of inconsistent connection. 

The biggest benefit lies in the high-quality video delivery on any network.

SRT makes it easier to stream over internet protocols (IP) with low end-to-end latency. As of now, there are very few protocol preferences for low-latency streaming. This is due to the fact that streaming over the public internet could create obstacles like packet loss and jitter. And SRT offers to fix this issue.

Additionally, this protocol encompasses protection against packet loss, jitter, and bandwidth fluctuations. This means if there’s an unstable network condition, your stream will likely stop. But it can almost instantly recover from such packet loss, and your audience will notice little to no problems while viewing.

Not only is it useful for high-quality video transmission and metadata exchange, SRT can also be utilized as a communication protocol.

Because this is an open-source protocol, developers can have access to the source code and customize it and create their own streaming solutions at technically no cost. 

Other features that benefit livestreaming include:

  • Timestamp-based packet delivery for better latency control with source time transmission
  • Control of the sender’s speed
  • Prevent packet dropping caused by a lost packet that was not recovered in time
  • Periodic NAK report for packet retransmission

This protocol gradually appears in many service providers and streaming platforms, including Castr — the first cloud-streaming service provider to support streaming using SRT. So now Castr’s users can incorporate this protocol into their streaming flow, besides other ingests like RTMP, RTSP, HLS, and MPEG-TS.

What Does This Mean for Streamers?

If you stream videos using the SRT protocol, you will surely benefit from its advantages. The protocol secures your video stream and makes sure all data are encrypted as they are being sent out. It also eliminates the burden of an exceptional internet connection, as this protocol guarantees the quality of your delivered video content. 

SRT secures your video stream and makes sure all data are encrypted as they are being sent out.

Better streams security

SRT protects your video content from contribution to distribution, thanks to the end-to-end 128/256 bit AES encryption.

Polished video quality

SRT ensures an optimal viewing experience for your audience with its protection against packet loss, jitter, and bandwidth fluctuations.

Low-latency streaming

SRT eliminates troublesome delays, making sure that everyone from different physical locations can watch the same content at the same time.


Haivision made this protocol free and open-source on GitHub with Mozilla Public License, any developer can have access to the source code.

Castr is the first cloud-based streaming service provider that supports streaming using the SRT protocol. Explore Castr livestream and multistream services here.

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