root/as3/Utils/src/org/libspark/utils/media/BeatTimer.as

package org.libspark.utils.media
{
        import flash.utils.getTimer;
        
        public class BeatTimer
        {
                public function BeatTimer()
                {
                }
                
                private var _bpm:Number;
                private var _startTime:uint;
                private var _beatPosition:Number;
                private var _phase:Number;
                private var _isOnBeat:Boolean = false;
                
                public function get bpm():Number
                {
                        return _bpm;
                }
                
                public function get beatPosition():Number
                {
                        return _beatPosition;
                }
                
                public function get phase():Number
                {
                        return _phase;
                }
                
                public function get isOnBeat():Boolean
                {
                        return _isOnBeat;
                }
                
                public function start(bpm:Number):void
                {
                        _bpm = bpm;
                        _startTime = getTimer();
                        update();
                }
                
                public function update():void
                {
                        var currentTime:uint = getTimer();
                        var beatInterval:Number = (60 * 1000) / _bpm;
                        var oldPosition:Number = _beatPosition;
                        
                        _beatPosition = (currentTime - _startTime) / beatInterval;
                        _phase = _beatPosition - int(_beatPosition);
                        _isOnBeat = int(oldPosition) != int(_beatPosition);
                }
        }
}