This page outlines the process for confirming audio and video bitrates for Live and On Demand streams. ON24 provides streams for webcast events using HTTP Live Streaming (HLS) and MPEG-DASH (MPD). The material provided here describes how a user can determine the bit rates for these streams, which are visible in the Dev Tools component of modern browsers. Both HLS and MPD streams are provided using Adjustable Bit Rate technology.  This means that multiple streams are normally available. 

Process Overview

• Live events Live Video, Sim-2-Live, and Broadcast Video) are streamed via HLS. The player starts the video at 300k, then steps up to 2500k if bandwidth is sufficient. 
• Pre-recorded events (Simu-live and On Demand) are streamed via MPD.  The player starts the video at 1000 Kbps and uses ABR to lower it to 500 Kbps if the network capacity available cannot support 1000 Kbps streams. Video clips in the slide area will stream at the same rate.
• Audio and video streams are two separate streams with HLS and MPD, as will be displayed below.
• Using Hive or Kollective changes the rules outlined here; please contact Platform Support if streaming information is needed for those environments.

The process for both MPD and HLS is the same. The browser fetches the streams directly.  As a consequence, stream components are directly visible.  The components are:

• Manifests – XML that describes the streams, available bit rates, etc.
• Stream segments, or “chunks”, which are the actual streams

It is the ability to visualize these elements which are described below.

The process, then, is:

1. Open Dev Tools in the target browser – Chrome and Edge are described below.
2. Locate Manifest files or stream chunks
   1. Manifest files show bit rates available, but metadata can be wrong in some situations
   2. Chunk files show the bit rate in the file name where ABR streams are in use.
   3. Interpret Chunk names to find audio vs video and stream speed. (see below)

ABR Stream Structure

ABR streams are structured differently in Live and On-Demand (OD) cases.  The “chunk” names outlined here address Live streams.  OD streams, which have “seg” names, are transcoded using different tools; one should focus on the manifest file to see the available rates.
 

Manifest Files

Manifest file structure and XML data elements are well documented on the web.  For example: 

• https://www.brendanlong.com/the-structure-of-an-mpeg-dash-mpd.html
• https://headendinfo.com/manifest-file/
• https://ottverse.com/hls-http-live-streaming-how-does-it-work/

Manifest files for HLS have the '.m3u8' file suffix, and those for MPD end with '.mpd'.</p>

Decoding Live Stream Names

The bit rates of the HLS streams are in the names displayed in developers tools. Since the HLS chunks contain both audio and video, the rates reflect the audio rate plus the video rate:

Decoding On-Demand Stream Names

On-Demand streams are named differently, and the bit rates are not apparent on the face of the stream names:

Bit rates can be found by accessing the manifest file

Accessing the Dev Tools

Chrome

1.  Click on the More Options icon

2.  Click on More tools

3.  Click on Developer Tools

4.  Click on the Network tab

Edge

1.  Click on Settings and select More

2.  Click on F12 Developer Tools

3.  Click on the Network tab