Adaptive extra splits

[master-of-zen]

Sets extra splits to 10 * fps if extra splits option was not provided, defaults to 240 if failed to get fps

[redzic]

This can be written with less lines like this:

match args.extra_split {
  Some(0) => None,
  Some(x) => Some(x),
  None => { /* rest of the code */ }
}