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ON24 Knowledge Center

Confirming Audio and Video Bitrates

This page outlines the process for confirming audio and video bitrates for Live and On Demand streams.

ON24 presently provides streams for webcast events using MPEG-DASH (MPD) and Flash/RTMP.  The material provided here describes how a user can determine the bit rates for MPD streams, which are visible in the Dev Tools component of modern browsers. 

Flash streams are still provided for Windows 7+ IE 11 environments, due to Microsoft’s decision not to support MPD streams in that environment.  Flash stream bit rates cannot be determined by this technique.  A ticket to Signal Operations is the simplest way to determine output bit rates.

MPD streams are provided using Adjustable Bit Rate technology.  This means that multiple streams are normally available; the player starts the video at 960k, then steps down to 500k if bandwidth is not sufficient. It does not attempt to step back up absent a console refresh.  Audio and video streams are two separate streams with 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.

Process Overview

Using MPD, the browser fetches the MPD 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, IE 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 what rates are available.

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

Decoding Live Stream Names

Audio and video streams are separate in MPD:

decoding live stream names1.png

The bit rates of the streams are in the names:

decoding live stream names2.png

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:

OD Stream1.png

Bit rates can be found by accessing the manifest file, which will be named stream.mpd:

od stream2.png

Accessing the Dev Tools

Chrome

1.  Click on the More Options icon

2.  Click on More tools

3.  Click on Developer Tools

chrome1.png

4.  Click on the Network tab

chrome2.png

Internet Explorer (IE 10/11)

1.  Click on the Tools icon

2.  Select F12 Developer Tools

ie1.png

3.  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

Edge1.png

Edge2.png

 

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