This Dual display function is base on Firefly-RK3288 platform, which can display
main screen on the mipi and display video on hdmi.
Turn on the function in setting.
When the video is playing，slid from the edge of the video to the other way, Then the video would be show on HDMI.
Click the synchronization button ,the mipi and hdmi will show the same contents.
MIPI: 1080P 30fps , HDMI: 1080P 30fps