Cutting and compressing video,reversing video,extracting image frames from video,extracting audio from video,add Fade In Fade Out effect,create fast and slow motion video using ffmpeg
Below link contains tutorial on using ffmpeg to edit videos-
https://androidlearnersite.wordpress.com/2017/03/17/ffmpeg-video-editor/
Below is the playstore link for the demo app-
https://play.google.com/store/apps/details?id=videoeditor.bhuvnesh.com.ffmpegvideoeditor