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.
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:
- Open Dev Tools in the target browser – Chrome, IE and Edge are described below.
- Locate Manifest files or stream chunks
- Manifest files show bit rates available, but metadata can be wrong in some situations
- Chunk files show the bit rate in the file name where ABR streams are in use.
- 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 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:
The bit rates of the streams are in the names:
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, which will be named stream.mpd:
Accessing the Dev Tools
1. Click on the More Options icon
2. Click on More tools
3. Click on Developer Tools
4. Click on the Network tab
Internet Explorer (IE 10/11)
1. Click on the Tools icon
2. Select F12 Developer Tools
3. Click on the Network tab
1. Click on Settings and select More
2. Click on F12 Developer Tools
3. Click on the Network tab