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50
51 #include "spectrum.h"
52 #include "utils.h"
53 #include <QByteArray>
54 #include <QAudioFormat>
55 #include <qmath.h>
56 #include <qendian.h>
57
generateTone(const SweptTone & tone,const QAudioFormat & format,QByteArray & buffer)58 void generateTone(const SweptTone &tone, const QAudioFormat &format, QByteArray &buffer)
59 {
60 Q_ASSERT(isPCMS16LE(format));
61
62 const int channelBytes = format.sampleSize() / 8;
63 const int sampleBytes = format.channelCount() * channelBytes;
64 int length = buffer.size();
65 const int numSamples = buffer.size() / sampleBytes;
66
67 Q_ASSERT(length % sampleBytes == 0);
68 Q_UNUSED(sampleBytes) // suppress warning in release builds
69
70 unsigned char *ptr = reinterpret_cast<unsigned char *>(buffer.data());
71
72 qreal phase = 0.0;
73
74 const qreal d = 2 * M_PI / format.sampleRate();
75
76 // We can't generate a zero-frequency sine wave
77 const qreal startFreq = tone.startFreq ? tone.startFreq : 1.0;
78
79 // Amount by which phase increases on each sample
80 qreal phaseStep = d * startFreq;
81
82 // Amount by which phaseStep increases on each sample
83 // If this is non-zero, the output is a frequency-swept tone
84 const qreal phaseStepStep = d * (tone.endFreq - startFreq) / numSamples;
85
86 while (length) {
87 const qreal x = tone.amplitude * qSin(phase);
88 const qint16 value = realToPcm(x);
89 for (int i=0; i<format.channelCount(); ++i) {
90 qToLittleEndian<qint16>(value, ptr);
91 ptr += channelBytes;
92 length -= channelBytes;
93 }
94
95 phase += phaseStep;
96 while (phase > 2 * M_PI)
97 phase -= 2 * M_PI;
98 phaseStep += phaseStepStep;
99 }
100 }
101