When going live, you have the ability to choose which qualities you want to stream in. This is entirely dependent on your hardware and Internet connection speed.
If you stream in multiple bitrates via Livestream Producer or Livestream Studio, or go live via RTMP through a third-party encoder, viewers will see the ability to adjust which quality they watch in the bottom right corner of the live player. By default, Auto is selected.
Auto will allow the player to automatically adjust which of the available qualities the viewer will see the stream based on their current connection speed. The player will always attempt to play the highest quality stream possible for that viewer's connection.
If you are streaming via a Mevo, a Broadcaster, the Livestream mobile app, or simply chose a single bitrate in Producer or Studio, then your viewers will only see your stream in that single quality. Livestream cannot transcode these streams into multiple bitrates and thus the player cannot adapt.