Independent of the main stream and sub-stream, the selectable resolutions cover all the HD resolutions of the main stream and all the SD resolutions of the sub-stream. The encoding parameters can be set separately, and can be selected according to network conditions and terminal display capabilities during remote preview Three streams of high-definition full frame, high-definition frame extraction and standard-definition full frame can be previewed, and the SVC function and area crop function can get a better preview experience.