package { import flash.utils.*; public class ADPCMDecoder { private var predictor:int; private var stepIndex:int; private var step:uint; public function ADPCMDecoder() { } public function init(p:int=0,si:int=0):void { predictor=p; stepIndex=si; step=stepTable[stepIndex]; } public function decodeBlock(block:ByteArray,blockSamples:uint,outBuff:Vector.):void { var sample:Number; var i:uint=0; for(;i>16) & 15; sample=parseNibble(nibble); outBuff[i++]=sample; } } private function parseNibble(nibble:uint):Number { stepIndex+=indexTable[nibble]; if(stepIndex<0) { stepIndex=0; } else if(stepIndex>88) { stepIndex=88; } var diff:uint = step >> 3; if(nibble & 1) diff += step >> 2; if(nibble & 2) diff += step >> 1; if(nibble & 4) diff += step; if(nibble & 8) { predictor-=diff; if(predictor<-32767) { predictor=-32767; } } else { predictor+=diff; if(predictor>32767) { predictor=32767; } } //predictor+=(nibbleToNumber(nibble) + 0.5) * step / 4; step=stepTable[stepIndex]; return predictor/32768.0; } private const stepTable:Array= [ 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, 50, 55, 60, 66, 73, 80, 88, 97, 107, 118, 130, 143, 157, 173, 190, 209, 230, 253, 279, 307, 337, 371, 408, 449, 494, 544, 598, 658, 724, 796, 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899, 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767 ]; private const indexTable:Array= [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8 ]; public static function nibbleToNumber(nibble:uint):Number { return [0,1,2,3,4,5,6,7,-8,-7,-6,-5,-4,-3,-2,-1][nibble]; } } }