[MPlayer-dev-eng] Feature Request: Audio timescale-pitch modification filter (fast forward)

[JustFillBug]

With mplayer, the sound is unbearable during fast forward/slow forward
play. Could someone provide an audio timescale filer that will
"shorten/stretching" sound play during fast forward/slow motion? It's
even good for learning foreign language... 

The timescale of audio is described in 

http://en.wikipedia.org/wiki/Audio_timescale-pitch_modification