A Comprehensive Guide to Video Streaming Protocols: RTMP, WebRTC, FTL, SRT

Navigating the world of streaming protocols can be daunting: which protocol best suits your needs? This comprehensive guide will demystify the most commonly used streaming protocols and help you determine which one is right for you.

We have discussed numerous aspects of live streaming, from setting up your equipment to becoming a Twitch affiliate. Now, it's time to delve into the intricacies of streaming protocols. What are they, and why are they important?

This article will explore the leading live streaming protocols, breaking down their functionalities and helping you make an informed decision. Contrary to what it may seem, understanding video streaming protocols does not require specialized education. Our goal is to simplify these concepts for you.

Understanding Streaming Protocols and Their Functionality

A streaming protocol is a set of rules for delivering multimedia over the Internet. It dictates how data is transmitted and how errors are managed during this process.

To clarify, a streaming protocol differs from a codec. A codec is a technology that compresses data (e.g., a video file) by removing unnecessary information to reduce file size. Streaming protocols are not the same as container formats, which determine how data is stored. Standard container formats for streaming video files include FLV, MP4, and MPEG-TS.

Before diving into specific protocols, it's essential to understand that they operate within the seven logical layers of network communication, each serving distinct functions.

TCP vs. UDP

The transport layer is crucial for content transmission to the end platform. The Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP) can be used. The primary difference is that TCP establishes a connection between devices to transfer data, whereas UDP skips this step.

Practically, UDP transmits smaller bits of information faster than TCP but without guaranteeing order or completeness, affecting data quality.

Popular Streaming Protocols

There are numerous streaming protocols, each serving a specific purpose. Here, we focus on the most widely used ones:

RTMP (Real-Time Messaging Protocol)

Overview: Developed by Macromedia and acquired by Adobe, RTMP remains a widely used protocol for live streaming.

Key Features: Provides a stable connection and low-latency communication. It transfers data in small packets, ensuring minimal interruptions.

Drawbacks: It is susceptible to interruptions due to low bandwidth and tight firewalls. It uses older codecs (H.264 for video and AAC for audio), which offer lower quality.

Codecs: H.264 (video), AAC (audio)

Latency: 3-30 seconds

Pros: Multicast support, low buffering, broad platform compatibility

Cons: Older codecs, lower security, relatively high latency

WebRTC (Web Real-Time Communication)

Overview: An open-source standard for real-time communication supported by most modern browsers.

Key Features: It enables high-quality streaming without additional plugins. It supports sub-second latency and uses adaptive bit rate technology to maintain video quality.

Drawbacks: Some instability due to ongoing development. Potential conflicts over codec use, particularly between VP8 and H.264.

Codecs: VP8, VP9, H.264, with AV1 support in progress

Latency: Less than one second

Pros: No plugins required, sub-second latency, supports modern codecs

Cons: Instability due to the development phase

FTL (Faster Than Light)

Overview: Developed by Mixer (Microsoft), FTL is designed for ultra-low latency streaming.

Key Features: It supports sub-second latency, facilitating real-time viewer interaction. It is integrated into popular streaming applications and platforms like Windows 10 and Xbox One.

Drawbacks: Slightly lower video quality and less stability. Limited support outside Mixer and Restream.

Codecs: H.264 (video), Opus (audio)

Latency: Less than one second

Pros: Ultra-low latency, real-time communication

Cons: Lower video quality, instability, limited support

SRT (Secure Reliable Transport)

Overview: An open-source protocol developed by Haivision and Wowza, seen as a future replacement for RTMP.

Key Features: It offers stable, high-quality streaming over suboptimal networks with sub-second latency and protects against jitters, bandwidth fluctuations, and packet loss.

Drawbacks: Limited playback options and platform support.

Codecs: Codec-agnostic

Latency: Less than one second

Pros: High quality, stability, sub-second latency, broad codec support

Cons: Limited platform support, no playback feature

Summary

In essence, streaming protocols are the rules governing data transfer over the Internet. We have explored four prominent live streaming protocols: RTMP, WebRTC, FTL, and SRT, each with unique advantages and limitations. Choosing the proper protocol depends on your specific needs and use case.

Future Predictions

While RTMP is currently prevalent, it is likely to be phased out. SRT and FTL are poised to vie for dominance, with WebRTC steadily growing as a leading protocol for real-time communication. Ultimately, the streaming landscape will continue to evolve, and any of these protocols could emerge as the industry standard.

By understanding these protocols, you can enhance your streaming capabilities and deliver high-quality, real-time content to your audience.