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
windowCreate(int size)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
windowCleanup()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. */
window(short * data,float * output,float preemp)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