title: Maintaining aspect ratio with FFmpeg
body: <p>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.</p>
  
  <p>As I am fixing the size of the screen to -s 720x400, if the aspect ratio of the original is 4:3, FFmpeg creates a 16:9 output file, screwing up the aspect ratio.</p>
  
  <p>Is there a setting that allows setting an aspect ratio as the main parameter, with size being adjusted (for example, by fixing an X or Y dimension only)?</p>