Often, when something technical works as it should, we don’t give much thought to how or why it works. This may be especially true when it comes to RTMP and livestreaming protocols. However, when you’re having difficulties with your own livestream events, understanding what it is and how it works might be helpful in troubleshooting. Here, we’ll go over the details of RTMP as it relates to livestreaming. You can gain an understanding of what RTMP really is, how it works and who uses it. Plus, we’ll show you some alternatives.
What is RTMP?
Behind the scenes of your computer, there are dozens of protocols at work. Protocols are the rules that inform your computer’s ability to interact with other computers even if they are not the same. For example, an office network has protocols that allow each user to access the same servers even if everyone has a different computer. Internet protocols allow computers to transmit messages, audio and video over the internet and be received by other unrelated computers. RTMP (Real-Time Messaging Protocol) is a specific set of protocols that help make livestreaming possible because the messages can be sent over the internet in real time.
RTMP was originally a proprietary protocol designed for sending audio and video with Adobe Flash Player. The flash player plug-in was mostly unrivaled in the early years. It was owned by Macromedia and eventually acquired by Adobe. Adobe later made a limited version of the protocol available to the public as the rest of the technologies advanced.
How does RTMP work?
If you’ve ever streamed a movie and found that the audio lags behind the actor’s mouth movements by a second or two, you might suddenly realize the importance of RTMP. In general terms, it transmits multiple types of information simultaneously between communicating devices. In this case, the multiple types of information are audio, video and messaging.
This livestreaming protocol creates a multi-directional path that sends you the image and sound. Although it sounds like a two-way system, it actually has a three-way handshake between the source (client) on one end and the receiver (server) on the other end. Not only does it send the information to the receiver, the receiver then sends a message back to confirm, which informs the source to continue sending. This gives it a stable connection with reliable timing.
Who uses RTMP?
Because of its low latency, RTMP has been widely used in video broadcasting. Typical ingest delay today is under two seconds. This is just enough time for radio and television broadcasters to cut back on liability (wardrobe malfunction, anyone?) if they move quickly. Imagine you’re streaming and a guest drops a forbidden f-bomb or you’re filming live from a ground-zero situation and it becomes a tragic scene. You have a few seconds to react and cut the video before it reaches viewers. Essentially, the total viewer latency depends on the playback protocol that follows.
Online, its role has shifted. Many servers, such as Nimble Streamer and Wowza Streaming Engine, accept RTMP. Major platforms like YouTube, Vimeo Live, Brightcove, Twitch, Facebook Live (RTMPS-only) and LinkedIn Live let creators push video to their servers with RTMP or RTMPS. They then convert the feed to HLS or DASH for playback.
Security matters, too. Most big sites now require or encourage RTMPS, which wraps RTMP in TLS encryption. Facebook mandated RTMPS in 2019, and YouTube highlights it in its encoder settings.
Amazon CloudFront dropped RTMP distributions at the end of 2020, showing that RTMP is now mainly a first-mile tool rather than a viewer-side solution.
Where can you find the RTMP information?
To set up your next livestream for simulcasting, you’ll need to find the RTMP (or RTMPS) URL on your streaming platform and embed it where you want the video to play. Here’s where to find it on some of the major platforms:
- YouTube: In Live Control Room, under Stream settings. By default, YouTube shows an RTMPS URL.
- Vimeo: With a live-enabled membership, choose Connect (RTMP) in Live Preview for the URL and key.
- Twitch: Check the Ingest Endpoints page for the server nearest you and copy the RTMP URL that matches.
- Facebook Live: Facebook provides an RTMPS URL in its Live Producer tool.
- LinkedIn Live: Approved creators see an RTMP or RTMPS URL in the event setup window.
What are some RTMP alternatives?
Obviously, if you’re creating video content for streaming, you want to be sure it’s the best it can be. Getting the right gear is important, of course, but finding alternatives to RTMP and livestreaming protocol might become an important part of that conversation. RTMP itself hasn’t evolved much since its creation, and as Flash fades from memory, newer technologies are gaining traction.
MPEG DASH and HLS
MPEG-DASH (Dynamic Adaptive Streaming over HTTP) and HLS (HTTP Live Streaming) are options that work similarly to each other. They use protocols that hold the audio and video data in chunks called packets. The path to the receiver is mapped, and if some of the data gets dropped, it’s quickly redirected to the mapped path. This means that the receiver will pause in a state of buffering before the playback actually begins so that all of the data arrives. It generates high-quality results, but the timeliness of live video is often lost.
Low-Latency HLS fixes much of that delay. LL-HLS and CMAF-based HLS can achieve end-to-end latencies of two to five seconds.
WebRTC and SRT
WebRTC (Web Real-Time Communication) and SRT (Secure Reliable Transport) are alternatives that definitely work towards upholding access to truly real-time streaming. They’re both free, open-source options. The focus in WebRTC is adaptive bitrate technology to eliminate latency entirely. Because it uses API support, it eliminates the need for plug-ins and downloads. SRT boasts secure streams that can traverse firewalls easily to reduce dependence on IT support while still giving you immediate delivery.
New kids on the block
Other emerging options include WHIP/WHEP (standardized WebRTC over HTTP), RIST (Reliable Internet Stream Transport) and Media over QUIC (MOQ), which aims for sub-second delivery on the new HTTP/3 foundation.
Ultimately, livestreaming protocols will likely evolve rapidly in the coming year. We advise you to learn as much as you can and start experimenting if you haven’t already.
