playing a specific interval of a video in mplayer using command line option

man mplayer

reveals:

-ss <time>: Seek to given time position
-endpos <[[hh:]mm:]ss[.ms]|size[b|kb|mb]>: Stop at given time or byte position

so you should be able to do what you want by simple using:

mplayer -ss 56 -endpos 3

Using mpv, a fork of MPlayer:

# specify start and length
mpv --start=3:20 --length=10 <file-name>

# specifying end
mpv --start=30 --end=40 <file-name>

# specifying end from end
mpv --start=80 --end=-90 <file-name>

More at mpv manual.