[MPlayer-users] when have -spualign/-subalign an effect?

[Paul Stoeber]

The command
  mplayer dvd://1 -dvd-device X.dvd -slang en
shows the subtitles, and
  mencoder dvd://1 -dvd-device X.dvd -oac copy -ovc lavc -o x.avi -slang en
renders them into x.avi.
However, adding
  -spualign {-1,0,1,2}
or
  -subalign {0,1,2}
to these commands has no effect.
When have -spualign/-subalign an effect?
Is it possible to change the placement of DVD subtitles?