Maintaining aspect ratio with FFmpeg

Question

I need to convert a bunch of video files using FFmpeg. I run a Bash file that converts all the files nicely, however there is a problem if a file converted is not in 16:9 format

Answer 1

Use force_original_aspect_ratio, from the ffmpeg trac:

ffmpeg -i input.mp4 -vf scale=720:400:force_original_aspect_ratio=decrease output.mp4