Speeding up playback of video with mplayer

So someone told me there is supposed to be a way to get mplayer to change play speed without changing pitch. I was even told that with sled10 it was automatic when you change the playspeed using the { and [ keys. Well, it does not seem to work for me but I did find a site that tells how to do it from the command line. http://mark.santaniello.net/archives/260
He recommends using the following command to get 50% or 1.5x increase with out a pitch chang:

mplayer -speed 1.5 -af ladspa=tap_pitch:tap_pitch:0:-33:-90:0 foo.avi

I like 100% increase or 2.0x so that would be:

mplayer -speed 2.0 -af ladspa=tap_pitch:tap_pitch:0:-50:-90:0 foo.avi

Now I need to find out how to make it happen with the ui speed change.