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DummyBackend: symmetric freq sweep: up/down

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This commit is contained in:
Robin Gareus 2014-09-24 18:46:54 +02:00
parent 6dfb8c5c8a
commit 186493687b
1 changed files with 15 additions and 4 deletions
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19
libs/backends/dummy/dummy_audiobackend.cc
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@ -1414,22 +1414,33 @@ void DummyAudioPort::setup_generator (GeneratorType const g, float const sampler
case SineSweepSwell:
{
_gen_period = 5 * samplerate + randi() % (int)(samplerate * 10.f);
_wavetable = (Sample*) malloc (_gen_period * sizeof(Sample));
_gen_period &= ~1;
_gen_perio2 = 1 | (int)ceilf (_gen_period * .89f); // Volume Swell period
const double f_min = 20.;
const double f_max = samplerate * .5;
const double g_p2 = _gen_period * .5;
#ifdef LINEAR_SWEEP
const double b = (f_max - f_min) / (2. * samplerate * _gen_period);
const double b = (f_max - f_min) / (2. * samplerate * g_p2);
const double a = f_min / samplerate;
#else
const double b = log (f_max / f_min) / _gen_period;
const double b = log (f_max / f_min) / g_p2;
const double a = f_min / (b * samplerate);
#endif
for (uint32_t i = 0 ; i < _gen_period; ++i) {
_wavetable = (Sample*) malloc (_gen_period * sizeof(Sample));
for (uint32_t i = 0 ; i < g_p2; ++i) {
#ifdef LINEAR_SWEEP
const double phase = i * (a + b * i);
#else
const double phase = a * exp (b * i) - a;
#endif
_wavetable[i] = (float)sin (2. * M_PI * (phase - floor (phase)));
}
for (uint32_t i = g_p2; i < _gen_period; ++i) {
const uint32_t j = _gen_period - i;
#ifdef LINEAR_SWEEP
const double phase = j * (a + b * j);
#else
const double phase = a * exp (b * j) - a;
#endif
_wavetable[i] = (float)sin (2. * M_PI * (phase - floor (phase)));
}