If you operate a business in the online media world or content delivery operations today, chances are that you will be working with various streaming technologies. Whether you’re streaming movies, publishing a live webinar, or developing video games, you will have noticed that the size of your audience continues to grow.
For live streaming alone, the global market grew from $1.24 billion in 2022 to $1.49 billion in 2023, a growth rate of 20.6%, according to The global live streaming market grew from $1.24 billion in 2022 to $1.49 billion in 2023, at a growth rate of 20.6%, according to Research and Markets. In fact, live streaming alone accounts for 23% of global viewing time, as per a report by Conviva, an online video optimization and analytics provider.
Key to the continued rise of these trends are the rapid adoption of a variety of streaming protocols, including SRT (Secure Reliable Transport) SRT and RTMP (Real-Time Messaging Protocol).
The Inner Workings of Streaming Protocols
Streaming protocols are integral components of online multimedia experiences. They determine how data is transmitted from a media source to an end user’s device, enabling real-time playback without the need for downloading the entire file. These protocols are specifically designed to tackle the challenges posed by varying network conditions, ensuring a smooth and uninterrupted streaming experience.
Video streaming protocols, in particular, focus on delivering video content efficiently. They take into account factors like latency, quality, and reliability to provide a seamless viewing experience. These protocols are the backbone of streaming platforms, enabling you to watch high-definition videos in real-time, engage in live broadcasts, and even participate in video conferencing.
What are SRT and RTMP?
Two commonly used streaming protocols are SRT and RTMP.
SRT is an open-source video transport protocol developed by Haivision and designed to connect two endpoints for delivering low-latency video and media streams across diverse networks, including the public internet. It was introduced in 2013 to enhance streaming performance over some types of networks and has become an industry standard, especially for time-sensitive streaming use cases like live sports and breaking news. SRT relies on an intelligent packet retransmit process called ARQ (Automatic Repeat reQuest) in addition to a UDP data flow, and with AES-128 and 256-bit encryption. Since becoming open source in 2017, SRT has gained rapid adoption.
So significant has the growth of SRT been in recent years that Haivision was given an Emmy Award in 2018 for pioneering reliable streaming and also received endorsements from major industry players like Microsoft, Adobe, Wowza, and Vimeo.
RTMP is a protocol that was originally designed for streaming to Adobe Flash players. Due to its TCP-based pack retransmit feature, it has garnered a reputation in the industry over the years. Despite Adobe ending support for Flash in 2020, RTMP is still widely used for live streaming video.
A Deep Dive
SRT and RTMP serve distinct purposes due to their respective strengths and weaknesses.
SRT
SRT offers end-to-end encryption and adaptive bitrate control, ensuring data security and smooth streaming in varying network conditions. It was created in 2013 out of a need to cut the cost of contribution from private networks and satellites. SRT excels in securely delivering low-latency media files across unpredictable internet speeds. Its end-to-end encryption, grounded in AES 128/256 encryption, ensures data security and prompt recovery of video and audio streams.
SRT stands as a solution to the common challenges in live video transport, addressing issues like packet loss, jitter, and bandwidth limitations. Providing a secure and reliable option for low-latency video transport, SRT employs advanced retransmission techniques for packet loss recovery. The protocol ensures precise timing recovery for video and audio streams, simplifies firewall traversal, and monitors network health between endpoints.
SRT employs the User Datagram Protocol (UDP), a connectionless protocol designed for real-time applications like video streaming. Operating with two key components – the Sender and the Receiver – SRT adapts to changing network conditions in real-time, and utilizes an error-correction mechanism called Automatic Repeat ReQuest (ARQ) for packet recovery, minimizing overhead and latency. Techniques such as packet loss caching, forward error correction (FEC), and adaptive bitrate streaming (ABR) are also part of the protocol, helping to optimize video streaming quality and reduce latency.
RTMP
On the other hand, RTMP provides low-latency performance and bidirectional data exchange, but it lacks built-in security features. A TCP-based protocol, it works by splitting the stream into smaller chunks of data, which allows them to be delivered faster. You can also adopt RTMP ingest, which uses the RTMP technology along with other streaming protocols like HLS or DASH to send live video streams to a media server for broadcast over the Internet. Support for RTMP is diminishing these days though, as other protocols like HLS and MPEG-DASH are being preferred by Content Delivery Networks (CDNs).
Comparing SRT and RTMP
Various tests have been conducted comparing the two protocols in streaming applications and the results show specific advantages and disadvantages depending on the use case and business priorities.
End-to-end Latency
In some tests comparing RTMP and SRT, it was found that the latter fared better when it came to end-to-end latency. Streams using SRT was more than twice as fast and, in case of dedicated hardware encoding and decoding equipment, sometimes even 5 to 12 times faster than those using RTMP.
Video Quality
On comparing the impact of the protocols on video quality, by increasing the bandwidth used for streaming, RTMP worked fine when both the sender and receiver were on the same continent. However, it failed at long distances at bitrates above 2 Mbps, while SRT had no problems streaming up to 20 Mbps to locations across the globe.
SRT: Strengths and Weaknesses
SRT prioritizes security and adaptive streaming, making it ideal for sensitive content. It has been gaining prominence in the streaming community due to its emphasis on security, reliability, and adaptability.
- Security: With end-to-end encryption and authentication, SRT ensures that your content remains secure throughout transmission.
- Reliability: SRT’s error correction mechanisms make it highly resilient to network issues, guaranteeing a smooth playback experience.
- Adaptive Bitrate Control: SRT’s adaptive bitrate control ensures that viewers receive the best possible quality based on their network conditions.
However, SRT is not without its weaknesses. It comes with a level of complexity and implementing SRT may require more technical expertise and resources compared to simpler protocols. It is also not compatible as other protocols and may not be supported by all streaming platforms. Lastly, the performance experienced with SRT streaming itself can vary depending on network conditions.
RTMP: Strengths and Weaknesses
RTMP excels in low-latency communication, suitable for live broadcasts and gaming.
- Low Latency: RTMP’s low-latency performance makes it an excellent choice for live streaming, gaming, and interactive applications.
- Wide Compatibility: Many media players and streaming platforms support RTMP, ensuring broad access to your content.
- Two-Way Communication: RTMP allows for bidirectional data exchange, making it suitable for interactive applications.
The weaknesses of RTMP are mainly to do with the lack of security features as RTMP does not provide built-in security features, making it vulnerable to security threats. It also does not do well with multi-language support, and support for ad insertion. Moreover, connectivity issues may arise when RTMP encounters firewalls, hindering its performance. Lastly, the proprietary nature of RTMP means you will have to consider licensing fees and the lack of community-driven development.
CDNetworks helps businesses with their live streaming needs through a number of solutions, while also being powered by our Content Delivery Network (CDN) capabilities. These include live streaming CDN solutions such as Media Acceleration Live Broadcast as well as all-in-one services like Cloud Live and Cloud VOD, both delivering real-time and seamless streaming experiences to global users. Our solutions also support both SRT and RTMP protocols, which means you can take advantage of our capabilities, no matter what your preference is.
