public void setPlaybackSpeed(float speed) {
        if(speed < 0) {
            throw new IllegalArgumentException("speed cannot be negative");
        }

        if(isInPlaybackState()) {
            mPlayer.setPlaybackSpeed(speed);
        }
        mPlaybackSpeedWhenPrepared = speed;
    }
Sets the playback speed. Can be used for fast forward and slow motion.
The speed must not be negative but can otherwise be set to any value. The player will not
skip frames though and only playback at the maximum speed that the device can decode and
process (setting 10x speed thus will not lead to an actual 10x speedup).

speed 0.5 = half speed / slow motion
speed 2.0 = double speed / fast forward
speed 0.0 equals to pause

@param speed the playback speed to set
@throws IllegalArgumentException if the speed is negative
MediaPlayer/src/main/java/net/protyposis/android/mediaplayer/VideoView.java