/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
// Generate a sinusoidal signal with optional onset and offset ramps.
#include <stdlib.h>
#include <math.h>
static inline short clipAndRound(float val) {
if (val > 32767.0)
return 32767;
if (val < -32768.0)
return -32768;
if (val >= 0.0)
return static_cast<short>(0.5 + val);
return static_cast<short>(val - 0.5);
}
/* Return a sinusoid of frequency freq Hz and amplitude ampl in output
of length numOutput. If ramp > 0.0, taper the ends of the signal
with a half-raised-cosine function. It is up to the caller to
delete[] output. If this call fails due to unreasonable arguments,
numOutput will be zero, and output will be NULL. Note that the
duration of the up/down ramps will be within the specified
duration. Note that if amplitude is specified outside of the
numerical range of int16, the signal will be clipped at +- 32767. */
void generateSinusoid(float freq, float duration, float sampleRate,
float amplitude, float ramp,
int* numOutput, short** output) {
// Sanity check
if ((duration < (2.0 * ramp)) || ((freq * 2.0) > sampleRate) || (ramp < 0.0)) {
*output = NULL;
*numOutput = 0;
return;
}
int numSamples = int(0.5 + (sampleRate * duration));
double arg = M_PI * 2.0 * freq / sampleRate;
short* wave = new short[numSamples];
int numRamp = int(0.5 + (sampleRate * ramp));
for (int i = 0; i < numSamples; ++i) {
float val = amplitude * sin(arg * i);
if (numRamp > 0) {
if (i < numRamp) {
float gain = (0.5 - (0.5 * cos((0.5 + i) * M_PI / numRamp)));
val *= gain;
} else {
if (i > (numSamples - numRamp - 1)) {
float gain = (0.5 - (0.5 * cos((0.5 + (numSamples - i - 1))
* M_PI / numRamp)));
val *= gain;
}
}
}
wave[i] = clipAndRound(val);
}
*numOutput = numSamples;
*output = wave;
}