tonegenerator.cpp Example File

multimedia/spectrum/app/tonegenerator.cpp
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#include "spectrum.h" #include "utils.h" #include <QByteArray> #include <QAudioFormat> #include <qmath.h> #include <qendian.h> void generateTone(const SweptTone &tone, const QAudioFormat &format, QByteArray &buffer) { Q_ASSERT(isPCMS16LE(format)); const int channelBytes = format.sampleSize() / 8; const int sampleBytes = format.channelCount() * channelBytes; int length = buffer.size(); const int numSamples = buffer.size() / sampleBytes; Q_ASSERT(length % sampleBytes == 0); Q_UNUSED(sampleBytes) // suppress warning in release builds unsigned char *ptr = reinterpret_cast<unsigned char *>(buffer.data()); qreal phase = 0.0; const qreal d = 2 * M_PI / format.sampleRate(); // We can't generate a zero-frequency sine wave const qreal startFreq = tone.startFreq ? tone.startFreq : 1.0; // Amount by which phase increases on each sample qreal phaseStep = d * startFreq; // Amount by which phaseStep increases on each sample // If this is non-zero, the output is a frequency-swept tone const qreal phaseStepStep = d * (tone.endFreq - startFreq) / numSamples; while (length) { const qreal x = tone.amplitude * qSin(phase); const qint16 value = realToPcm(x); for (int i=0; i<format.channelCount(); ++i) { qToLittleEndian<qint16>(value, ptr); ptr += channelBytes; length -= channelBytes; } phase += phaseStep; while (phase > 2 * M_PI) phase -= 2 * M_PI; phaseStep += phaseStepStep; } }

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