First i have opened the ffmpeg media encoder in my android smartphone and tried to convert a small video file and fortunately this app has option to view all options in command window.
After that I have noted down the command in pc notepad and after that I have issued the command in the windows command prompt and Linux terminal emulator.
The quality of output video file generated is very good. The fact is that the quality of video file generated using ffmpeg guis like format factory and tragator is not good as the quality of video file generated by ffmpeg command itself.
I am giving the command seen in the android smartphone as below
ffmpeg -y -i /storage/emulated/0/FFMPEG/to convert/sample.mp4 -c:v libx265 -b:v 400k -c:a libfdk_aac -b:a 64k -ar 44100 /storage/emulated/0/FFMPEG/sample.mp4.
I have posted the current because it may be useful for you.