1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 5 * use this file except in compliance with the License. You may obtain a copy of 6 * 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, WITHOUT 12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 13 * License for the specific language governing permissions and limitations under 14 * the License. 15 */ 16 17 #include "Window.h" 18 19 #include <stdlib.h> 20 #include <math.h> 21 22 void Window::windowCreate(int size) { 23 if (mWindowWeights && (mWindowSize < size)) { 24 delete [] mWindowWeights; 25 mWindowWeights = NULL; 26 mWindowSize = 0; 27 } 28 if (!mWindowWeights) { 29 mWindowWeights = new float[size]; 30 } 31 if (mWindowSize != size) { 32 double arg = M_PI * 2.0 / size; 33 mWindowSize = size; 34 for (int i = 0; i < size; ++i) { 35 mWindowWeights[i] = 0.5 - (0.5 * cos((i + 0.5) * arg)); 36 } 37 } 38 } 39 40 void Window::windowCleanup() { 41 mWindowSize = 0; 42 delete [] mWindowWeights; 43 mWindowWeights = NULL; 44 } 45 46 /* Multiply the signal in data by the window weights. Place the 47 resulting mWindowSize floating-point values in output. If preemp 48 is != 0.0, apply a 1st-order preemphasis filter, and assume that 49 there are mWindowSize+1 samples available in data. */ 50 void Window::window(short* data, float* output, float preemp) { 51 if (preemp == 0.0) { 52 for (int i = 0; i < mWindowSize; ++i) 53 output[i] = data[i] * mWindowWeights[i]; 54 } else { 55 for (int i = 0; i < mWindowSize; ++i) 56 output[i] = (data[i+1] - (preemp * data[i])) * mWindowWeights[i]; 57 } 58 } 59 60
