Initial version. Allows listing and measuring

Measurer.cpp

@@ -0,0 +1,108 @@
+#include "Measurer.h"
+#include "Generator.h"
+#include "fft.h"
+
+#include <QAudioInput>
+#include <QAudioOutput>
+#include <QDateTime>
+#include <QCoreApplication>
+#include <qendian.h>
+
+#include <vector>
+
+using namespace std;
+
+Measurer::Measurer(QAudioDeviceInfo input, QAudioDeviceInfo output, MeasureChannel channel)
+    : input(input), output(output), channel(channel)
+{
+}
+
+long double CurrentTime()
+{
+	return QDateTime::currentMSecsSinceEpoch() / 1000.0;
+}
+
+float Measurer::Measure(float duration)
+{
+	QAudioFormat format;
+	format.setSampleRate(SAMPLE_RATE);
+	format.setChannelCount(2);
+	format.setSampleSize(16);
+	format.setCodec("audio/pcm");
+	format.setByteOrder(QAudioFormat::LittleEndian);
+	format.setSampleType(QAudioFormat::SignedInt);
+
+	// configure generator of single-tone signal
+	auto device = new Generator(format, duration * 1000000, TONE_FREQUENCY, channel == MeasureChannel::Right);
+	device->start();
+	// begin outputting data to device
+	QAudioOutput * audio_output = new QAudioOutput(output, format);
+	audio_output->start(device);
+	// begin reading of samples from input
+	QAudioFormat input_format(format);
+	input_format.setChannelCount(1);
+	QAudioInput *audio_input = new QAudioInput(input, input_format);
+	auto reading_device = audio_input->start();
+	auto start = CurrentTime();
+	QByteArray input_buffer;
+	while (CurrentTime() < start + duration)
+	{
+		QCoreApplication::processEvents();
+		input_buffer += reading_device->readAll();
+	}
+	audio_input->stop();
+	audio_output->stop();
+	device->stop();
+	auto result = ProcessData(input_buffer);
+	delete audio_input;
+	delete audio_output;
+	delete device;
+	return result;
+}
+
+float Measurer::ProcessData(QByteArray data)
+{
+	// convert byte data to sample array
+	vector<float> samples;
+	// note that we fixed format to be little-endian, two-byte, signed
+	for (int i = 0; i < data.count(); i += 2)
+	{
+		int t = qFromLittleEndian<qint16>(data.data() + i);
+		samples.push_back(t / 32767.0);
+	}
+	// cut off starting and ending silence
+	int left_pos = 0;
+	while (left_pos < (int)samples.size() && abs(samples[left_pos]) < 1e-4) left_pos++;
+	int right_pos = (int)samples.size() - 1;
+	while (right_pos >= 0 && abs(samples[right_pos]) < 1e-4) right_pos--;
+	int len = right_pos - left_pos + 1;
+	int pow = 1, m = 0;
+	while (2 * pow <= len)
+	{
+		pow <<= 1;
+		m++;
+	}
+	Complex *d = new Complex[pow];
+	for (int i = 0; i < pow; i++)
+	{
+		d[i] = Complex(samples[left_pos + i], 0);
+	}
+	FFT(d, pow, false);
+	float max = -1;
+	int argmax = 0;
+	for (int i = 0; i < pow; i++)
+	{
+		float amp = (float)sqrt(d[i].real() * d[i].real() + d[i].imag() * d[i].imag());
+		if (amp > max)
+		{
+			max = amp;
+			argmax = i;
+		}
+	}
+	float desired = TONE_FREQUENCY * pow / SAMPLE_RATE;
+	if (abs(desired - argmax) < 1e-3)
+	{
+		return max / pow;
+	}
+	return nan("");
+}