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 // Generate a sinusoidal signal with optional onset and offset ramps.
18
19 #include <stdlib.h>
20 #include <math.h>
21
clipAndRound(float val)22 static inline short clipAndRound(float val) {
23 if (val > 32767.0)
24 return 32767;
25 if (val < -32768.0)
26 return -32768;
27 if (val >= 0.0)
28 return static_cast<short>(0.5 + val);
29 return static_cast<short>(val - 0.5);
30 }
31
32 /* Return a sinusoid of frequency freq Hz and amplitude ampl in output
33 of length numOutput. If ramp > 0.0, taper the ends of the signal
34 with a half-raised-cosine function. It is up to the caller to
35 delete[] output. If this call fails due to unreasonable arguments,
36 numOutput will be zero, and output will be NULL. Note that the
37 duration of the up/down ramps will be within the specified
38 duration. Note that if amplitude is specified outside of the
39 numerical range of int16, the signal will be clipped at +- 32767. */
generateSinusoid(float freq,float duration,float sampleRate,float amplitude,float ramp,int * numOutput,short ** output)40 void generateSinusoid(float freq, float duration, float sampleRate,
41 float amplitude, float ramp,
42 int* numOutput, short** output) {
43 // Sanity check
44 if ((duration < (2.0 * ramp)) || ((freq * 2.0) > sampleRate) || (ramp < 0.0)) {
45 *output = NULL;
46 *numOutput = 0;
47 return;
48 }
49 int numSamples = int(0.5 + (sampleRate * duration));
50 double arg = M_PI * 2.0 * freq / sampleRate;
51 short* wave = new short[numSamples];
52 int numRamp = int(0.5 + (sampleRate * ramp));
53 for (int i = 0; i < numSamples; ++i) {
54 float val = amplitude * sin(arg * i);
55 if (numRamp > 0) {
56 if (i < numRamp) {
57 float gain = (0.5 - (0.5 * cos((0.5 + i) * M_PI / numRamp)));
58 val *= gain;
59 } else {
60 if (i > (numSamples - numRamp - 1)) {
61 float gain = (0.5 - (0.5 * cos((0.5 + (numSamples - i - 1))
62 * M_PI / numRamp)));
63 val *= gain;
64 }
65 }
66 }
67 wave[i] = clipAndRound(val);
68 }
69 *numOutput = numSamples;
70 *output = wave;
71 }
72