请问如下两段代码什么意思?

var l = this._x;
var t = this._y;
btn.onPress = function ()
{
    startDrag (this._parent, false, l - 146, t, l, t);
};
btn.onRelease = btn.onReleaseOutside = function ()
{
    stopDrag ();
};
onEnterFrame = function ()
{
    vol = (this._x - l) / 146 * 100 + 100;
    _parent.s.setVolume(vol);
};




var l = this._x;
var t = this._y;
var b = true;
btn.onPress = function()
{
       b = false;
       startDrag(this._parent, false, l, t, l + 146, t);
};
btn.onRelease = btn.onReleaseOutside = function ()
{
       _parent.s.start((this._parent._x - 475) / 146 * (_parent.s.duration / 1000),1);
       stopDrag();
       b = true;
};
onMouseMove = function ()
{
       if (b == true)
       {
              this._x = _parent.s.position / _parent.s.duration * 146 + l;
       }
       // end if
};

第一个是声音控制，第二个是控制音乐播放头~