Yes, we fully support multi-bitrate live streaming.
The DaCast player detects automatically the different bitrates of your live stream and allows the viewer to choose between them.
You do first need to set up this option in your encoder directly.
Also, you need a large enough upload speed to support the multi-bitrates as well. For example, 200 kbps + 600 kbps would be the same as broadcasting at 800kbps. You would likely need an upload speed of over 1MB a second.