ABRManager

Overview

The ABRManager (ABR for Adaptive BitRate) is a class which facilitates the choice between multiple audio/video qualities in function of the current bandwidth, the network capacities and other specific settings set by the client.

It does so by receiving various values such as:

• when network requests begin, progresses or end
• stats about the bandwidth of the user
• the current status of the buffer (how much of the buffer is left etc.)
• DOM events
• user settings (maximum authorized bitrate/width etc.)
• the available qualities

With all those variables in hand, it then proposes the quality which seems to be the most adapted, that is the quality which:

• will respect user settings (example: a Maximum bitrate is set)
• will maximize the user experience (example: a quality too high for the network to handle would lead to excessive re-bufferings, but a too low would be not as pleasant to watch)

In order to estimate the quality that maximizes the playback experience, the ABR relies on two “estimators”. The bandwidth estimator picks a quality from network conditions. The buffer based estimator relies on buffering conditions to make his choices.