成员的完整列表，这些成员属于 com.netease.lava.nertc.sdk.video.NERtcVideoStreamType,包括所有继承而来的类成员

kNERtcVideoStreamTypeFourth	com.netease.lava.nertc.sdk.video.NERtcVideoStreamType
kNERtcVideoStreamTypeMain	com.netease.lava.nertc.sdk.video.NERtcVideoStreamType
kNERtcVideoStreamTypeSub	com.netease.lava.nertc.sdk.video.NERtcVideoStreamType
kNERtcVideoStreamTypeThird	com.netease.lava.nertc.sdk.video.NERtcVideoStreamType