onStart method
@detail callback
@author wangzhanqiang
@brief Prompt custom encoded frames to start pushing callbacks.
After receiving this callback, you can call pushExternalEncodedVideoFrame{@link #RTCEngine#pushExternalEncodedVideoFrame} to push a custom encoded video frame to the SDK
@param streamId The ID of the encoded stream that can be pushed
@param streamInfo The properties of the encoded stream that can be pushed
Implementation
FutureOr<void> onStart(String streamId, StreamInfo streamInfo) async {}