2: Subscribe to the low-quality video stream when the network conditions worsen, and subscribe to audio only when the conditions become too poor to support video transmission.
DISABLE
DISABLE: = 0
0: Disable the fallback.
HIGH_STREAM_LAYER1
HIGH_STREAM_LAYER1: = 3
HIGH_STREAM_LAYER2
HIGH_STREAM_LAYER2: = 4
HIGH_STREAM_LAYER3
HIGH_STREAM_LAYER3: = 5
HIGH_STREAM_LAYER4
HIGH_STREAM_LAYER4: = 6
HIGH_STREAM_LAYER5
HIGH_STREAM_LAYER5: = 7
HIGH_STREAM_LAYER6
HIGH_STREAM_LAYER6: = 8
LOW_STREAM
LOW_STREAM: = 1
1: Automatically subscribe to the low-video stream under poor network conditions.
The stream fallback option. Set the stream fallback option when calling setStreamFallbackOption.