How to trim the video using FFMPEG library in andr

Question

In My Project,uploading the video ( duration is 10 seconds only) to amazon .So when i choose video from library of 30 seconds then i want trim the video to 10 seconds or may be less.I am using Mp4 Parser for trimming the videos but when trim the portrait video,it is converting to landscape mode and the video rotation also changes.I done lot of research in google but no solution lastly I found one solution that FFMPEG library.In windows the ffmpeg library is not building.So what can I do now?I am new to the FFMPEG library.Please give the suggestions how to build the FFMPEG library in android.Thanks in advance