Encoding for Adaptive Streaming - an Overview

posted on 26 Apr 2012 17:27 by jodunk in IPTV

Encoding for Adaptive Streaming - an Overview

I've been researching how to encode video for adaptive bitrate streaming, specifically the encoding parameters for the different files streamed in the process. Here's what I found for Adobe's Dynamic Streaming, Apple's HTTP Live Streaming and Microsoft's Smooth Streaming.

Adobe's Dynamic Streaming

For Dynamic Streaming, I found an excellent article by Larry Bouthillier on the StreamingMedia web site. EntitledHow to do Dynamic Streaming with Flash Media Server, the article covers how to encode multiple files (with a link back to Adobe's recommended encoding settings), tests the streaming switching capabilities of three different Flash Players and provides the necessary code for dynamic streaming in each player. Regarding the encoding side, Larry conluded that:

Here are the parameters that Larry tested with, using a key frame interval of two seconds for all files:

adaptive 1.png

Here's what he found:

The three most crucial success factors turned out to be:  

  1. the keyframe interval of your encodings,
  2. the bufferlength configuration of your player, and
  3. the bitrate spacing and quantity of your media files.

I'll let you jump back over to his article for more detail on Larry's conclusions. 

HTTP Live Streaming

For Apple's HTTP Live Streaming,you can refer to Apple's own white paper on the subject.

What settings are recommended for a typical HTTP stream, with alternates, for use with the media segmenter from Apple?

Your encoder should produce MPEG-2 transport stream (.ts) files with the following characteristics for the Apple segmenter:

  • H.264 Baseline 3.0 video

  • Keyframes every 3 seconds

  • HE-AAC (version 1) stereo audio at 44.1 kHz

  • Four streams:

    • Cellular Fallback—Audio only or audio with still image, 64 Kbps

    • Low—96 Kbps video, 64 Kbps audio

    • Medium—256 Kbps video, 64 Kbps audio

    • High—800 Kbps video, 64 Kbps audio

I wrote an article on streaming to the iPhone for Digital Content Producer, and Turner Broadcasting was kind enough to share the encoding parameters that they used for the PGA Championship. Here they are:

adaptive 3.png

Microsoft's Smooth Streaming

For Smooth Streaming, the best reference I could find was Ben Waggoner's post here. Here are the parameters that Ben recommended encoding to:

adaptive 2.png