Dual video mode splits the scene on the viewfinder into two views. You can view and record a scene with the rear and front camera simultaneously.
1. Open 
Camera.2. Select More.
3. Tap
Dual video.4. Tap
to adjust the places of front and rear views on the viewfinder.5. Tap · to start shooting.
6. Tap
to stop shooting.Tip
You can tap to enlarge a view and narrow the other view.