Answers for "how to take storage permission from user"

crop video from specific time to specific time ffmpeg

ffmpeg -ss 00:01:00 -i input.mp4 -to 00:02:00 -c copy output.mp4
# Triming in ffmpeg

ffmpeg trim video

ffmpeg -ss 00:00:30.0 -i input.wmv -c copy -t 00:00:10.0 output.wmv
ffmpeg -ss 30 -i input.wmv -c copy -t 10 output.wmv

write storage permission android

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />