1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package org.drrickorang.loopback; 18 19 20 /** 21 * This class contains functions that can be reused in different classes. 22 */ 23 24 public class Utilities { 25 26 27 /** Multiply the input array with a hanning window. */ 28 public static void hanningWindow(double[] samples) { 29 int length = samples.length; 30 final double alpha = 0.5; 31 final double beta = 0.5; 32 double coefficient; 33 for (int i = 0; i < length; i++) { 34 coefficient = (Constant.TWO_PI * i) / (length - 1); 35 samples[i] *= alpha - beta * Math.cos(coefficient); 36 } 37 38 } 39 40 41 /** Round up to the nearest power of 2. */ 42 public static int roundup(int size) 43 { 44 // Integer.numberOfLeadingZeros() returns 32 for zero input 45 if (size == 0) { 46 size = 1; 47 } 48 49 int lz = Integer.numberOfLeadingZeros(size); 50 int rounded = 0x80000000 >>> lz; 51 // 0x800000001 and higher are actually rounded _down_ to prevent overflow 52 if (size > rounded && lz > 0) { 53 rounded <<= 1; 54 } 55 return rounded; 56 } 57 58 } 59
