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Video Streaming Protocols

Joseph Scrivens
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The point of this article is to do a little comparison of the popular and deprecated/old video streaming formats. Hopefully this will allow you to make a decision as to which is best for your streaming application.

This article applies to products like:

 

 

  • RTMP - Real-Time Messaging Protocol

    • Comes from the Adobe Flash stable of products
    • Works with YouTube Live, Facebook Live, Twitch, Periscope and so on
    • TCP-based protocol, uses port 1935 by default
    • Requires a dedicated streaming server
    • Latency of around 5 seconds, similar to that of cable TV broadcasts
    • Not scalable (1-1 connections, typically) and not optimized for quality of experience
      • With the live CDNs above (YouTube Live and so on), you serve the RTMP/RTMPS stream to them, and they handle the one-to-many streaming using different  protocols
    • Adobe won't update Flash after the end of 2020

 

  • RTMPS

    • As above, but using TLS/SSL security protocols

 

  • HDS - HTTP Dynamic Streaming

    • Adobe's next step from RTMP
    • Flash-based (uh oh) but with adaptive streaming
    • Low latency (5-10 seconds or so), but not as good as RTMP

 

  • RTSP - Real-Time Streaming Protocol

    • Similar to HLS (discussed below)
    • Designed for low-latency (2 seconds or so) streaming for things like IP-camera feeds, IoT devices and so on
    • Not great browser-support for RTSP (generally involves conversion via an intermediate server to some other format like RTMP, HLS, etc.)

 

  • MPEG-DASH - Dynamic Adaptive Streaming over HTTP

    • Supports adaptive-bitrate streaming, so that anyone viewing will get the best video quality that their internet connection can produce
    • Works with a huge range of codecs
    • Limited support for Apple iOS and Safari devices
    • High latency of 30 seconds or more

 

  • HLS - HTTP Live Streaming

    • This one came from Apple, specifically designed so that they didn't have to support Flash on iPhones
    • Most widely-used streaming protocol today
    • Supported by phones, browsers, smart TVs and a lot more
    • Has adaptive-bitrate streaming support
    • Now supports H.265 codecs, so you're getting twice the video quality for the same file size as H.264
    • Latency is high at 20-30 seconds or worse (more on this below) - encoding, transcoding, distribution, default playback buffer and more
    • Not ideal for streaming an event/service time-critical events (like horse racing, or New Year's Eve), but works well for everything else.

 

  • LL-HLS - Low Latency HLS

    • Originally Twitter's Periscope platform came up with LHLS, a proprietary offshoot from HLS that reduced latency to around 2-5 seconds
    • In 2019, Apple announced LL-HLS as a more open version to get those times down to the 2-5 second range
    • Not broadly used (as of June 2020), but likely to become a big player

 

  • Web-RTC - Web Real Time Communication

    • Lowest latencies, at under a second
    • Designed purely for real-time viewing
      • Think of a PTZ camera control
      • Or a web conference or video chat
    • Supported mainly by web browsers
    • Not designed to push content to a lot of viewers, so not suitable for things like live sports broadcasts

 

From a 2019 streaming report, made by the experts at https://www.wowza.com/blog/streaming-protocols, we have:

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