Stream fallback option.
2: Under unreliable uplink network conditions, the published video stream falls back to audio only. Under unreliable downlink network conditions, the remote video stream first falls back to the low-stream (low resolution and low bitrate) video; and then to an audio-only stream if the network condition deteriorates.
0: No fallback behavior for the local/remote video stream when the uplink/downlink network condition is unreliable. The quality of the stream is not guaranteed.