Sketch20100506.as

// 2010-05-08 koyachi
// Frequency selected sound energy algorithm 1
// http://www.gamedev.net/reference/programming/features/beatdetection/
package {
    import flash.display.*;
    import flash.text.*;
    import flash.net.*;
    import flash.media.*;
    import flash.events.*;
    import flash.utils.*;
    public class Sketch20100506 extends Sprite {
        private var tf:TextField;
        private var textFormat:TextFormat;
        private var sound:Sound = new Sound();
        private var playSound:Sound = new Sound();
        private var sprite:Sprite = new Sprite();

        private var samplesL:Array = [];
        private var samplesR:Array = [];

        private var energyHistory:Array = [];
        private var beatDetected:Boolean = false;

        [SWF(background=0xFFFFFF,width=800,height=600,frameRate=30)]
        public function Sketch20100506() {
//            var url:URLRequest = new URLRequest('./renai_circulation.mp3');
            var url:URLRequest = new URLRequest('./f.x.n.c..mp3.ab160.mp3');
            sound.load(url);
            sound.addEventListener(Event.COMPLETE, onLoaded);
            tf = new TextField();
            tf.width = 800;
            tf.height = 600;
            tf.text = '2010-05-06, hello.';

            textFormat = new TextFormat();
            textFormat.size = 8;
            tf.defaultTextFormat = textFormat;

            addChild(tf);
            addChild(sprite);
            addEventListener(Event.ENTER_FRAME, processSamples);
        }

        public function onLoaded(event:Event):void {
            playSound.addEventListener(SampleDataEvent.SAMPLE_DATA, processSound);
            playSound.play();
        }

        public function processSound(event:SampleDataEvent):void {
            var resultBuffer:ByteArray = new ByteArray();
            var sourceBuffer:ByteArray = new ByteArray();
            var len:Number = 4096;
            var samples:Number = sound.extract(sourceBuffer, len);
            var str:String = samples + '.\nhohoho\n';
            sourceBuffer.position = 0;
            samplesL = [];
            samplesR = [];
            var energy:Number = 0;
            var count:uint=0;
            while (sourceBuffer.bytesAvailable > 0) {
                count++;
                var l:Number = sourceBuffer.readFloat();
                var r:Number = sourceBuffer.readFloat();
                samplesL.push(l);
                samplesR.push(r);
                resultBuffer.writeFloat(l);
                resultBuffer.writeFloat(r);
                energy += l*l + r*r;
// change pitch
//                if (sourceBuffer.bytesAvailable > 0) {
//                    sourceBuffer.position += 4;
//                }
            }
            event.data.writeBytes(resultBuffer);

            var optimizedE:Number = 0.0;
            for(var i:uint=0; i < energyHistory.length; i++) {
                // 2乗だとほとんど検出しない
                //optimizedE += energyHistory[i] * energyHistory[i];
                optimizedE += energyHistory[i];
            }
            optimizedE *= (1.0 / 43);
//            beatDetected = isBeat(energy, optimizedE);

            var v:Number = 0;
            for(i=0; i < energyHistory.length; i++) {
                v += energyHistory[i] - optimizedE;
            }
            v *= (1.0 / 43);
            beatDetected = isBeat2(energy, optimizedE, v);

            energyHistory.push(energy);
            if (energyHistory.length > (44032 / 1024)) { // 43
                energyHistory.shift();
            }

            str = [str, count,energy, optimizedE, (beatDetected ? 'BEAT' : '...'), ''].join('\n');
            str += energyHistory.map(function(eh:Number, index:int, list:Array):String{return '[' + eh + ']'}).join('\n');
            tf.text = str;
        }

        public function isBeat(currentEnergy:Number, optimizedE:Number):Boolean {
            var C:Number = 1.3;
//            var C:Number = 1.0;
            return (currentEnergy > C * optimizedE) ? true : false;
        }

        public function isBeat2(currentEnergy:Number, optimizedE:Number, v:Number):Boolean {
            var C:Number = (-0.0025714 * v) + 1.5142857;
            return (currentEnergy > C * optimizedE) ? true : false;
        }

        public function processSamples(event:Event):void {
            var g:Graphics = sprite.graphics;
            g.clear();
            var w:uint = 800;
            var h:uint = 600;

            var prev_lx:uint = 0;
            var prev_ly:uint = h/2;
            var cur_lx:uint = 0;
            var cur_ly:uint = 0;

/*
            var prev_rx:uint = 0;
            var prev_ry:uint = h/2;
            var cur_rx:uint = 0;
            var cur_ry:uint = 0;
*/
            if (beatDetected) {
                g.lineStyle(2, 0x0000ff);
            }
            else {
                g.lineStyle(1, 0x8080ff);
            }
            g.moveTo(prev_lx, prev_ly);
            for (var i:uint=0; i < samplesL.length; i++) {
//                g.lineStyle(1, 0xff0000ff, 1.0);
//                g.moveTo(prev_lx, prev_ly);
                cur_lx = w * i / samplesL.length;
                cur_ly = samplesL[i] * (h / 2) + (h / 2);
//                g.lineStyle(1, 0xff0000ff, 1.0);
                g.lineTo(cur_lx, cur_ly);
//                prev_lx = cur_lx;
//                prev_ly = cur_ly;

/*
                g.lineStyle(1, 0x00ff00ff, 1.0);
                g.moveTo(prev_rx, prev_ry);
                cur_rx = w * i / samplesR.length;
                cur_ry = samplesR[i] * (h / 2) + (h / 2);
                g.lineStyle(1, 0xff0000ff, 1.0);
                g.lineTo(cur_rx, cur_ry);
                prev_rx = cur_rx;
                prev_ry = cur_ry;
*/
            }
        }
    }
}