Loopped slider replace slide effect to fade-out/fade-in effect on the prev and next slide functions?

Question

function animate(dir,clicked){
u = true;
switch(dir){

                            case 'next':
                                    t = t+1;
                                    m = (-(t*w-w));
                                    current(t);
                                    if(o.autoHeight){autoHeight(t);}
                                    $(o.slides,obj).animate({left: m}, o.slidespeed,function(){
                                            if (t===s+1) {
                                                    t = 1;
                                                    $(o.slides,obj).css({left:0},function(){$(o.slides,obj).animate({left:m})});                                                    
                                                    $(o.slides,obj).children(':eq(0)').css({left: 0});
                                                    $(o.slides,obj).children(':eq('+(s-1)+')').css({ position:'absolute',left:-w});                         
                                            }
                                            if (t===s) $(o.slides,obj).children(':eq(0)').css({left:(s*w)});
                                            if (t===s-1) $(o.slides,obj).children(':eq('+(s-1)+')').css({left:s*w-w});
                                            u = false;
                                    });                                     
                                    break; 
                            case 'prev':
                                    t = t-1;
                                    m = (-(t*w-w));
                                    current(t);
                                    if(o.autoHeight){autoHeight(t);}
                                    $(o.slides,obj).animate({left: m}, o.slidespeed,function(){
                                            if (t===0) {
                                                    t = s;
                                                    $(o.slides,obj).children(':eq('+(s-1)+')').css({position:'absolute',left:(s*w-w)});
                                                    $(o.slides,obj).css({left: -(s*w-w)});
                                                    $(o.slides,obj).children(':eq(0)').css({left:(s*w)});
                                            }
                                            if (t===2 ) $(o.slides,obj).children(':eq(0)').css({position:'absolute',left:0});
                                            if (t===1) $(o.slides,obj).children(':eq('+ (s-1) +')').css({position:'absolute',left:-w});
                                            u = false;
                                    });
                                    break;