Qt Reference Documentation

engine.cpp Example File

demos/spectrum/app/engine.cpp
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 #include "engine.h"
 #include "tonegenerator.h"
 #include "utils.h"

 #include <math.h>

 #include <QCoreApplication>
 #include <QMetaObject>
 #include <QSet>
 #include <QtMultimedia/QAudioInput>
 #include <QtMultimedia/QAudioOutput>
 #include <QDebug>
 #include <QThread>
 #include <QFile>

 //-----------------------------------------------------------------------------
 // Constants
 //-----------------------------------------------------------------------------

 const qint64 BufferDurationUs       = 10 * 1000000;
 const int    NotifyIntervalMs       = 100;

 // Size of the level calculation window in microseconds
 const int    LevelWindowUs          = 0.1 * 1000000;

 //-----------------------------------------------------------------------------
 // Helper functions
 //-----------------------------------------------------------------------------

 QDebug& operator<<(QDebug &debug, const QAudioFormat &format)
 {
     debug << format.frequency() << "Hz"
           << format.channels() << "channels";
     return debug;
 }

 //-----------------------------------------------------------------------------
 // Constructor and destructor
 //-----------------------------------------------------------------------------

 Engine::Engine(QObject *parent)
     :   QObject(parent)
     ,   m_mode(QAudio::AudioInput)
     ,   m_state(QAudio::StoppedState)
     ,   m_generateTone(false)
     ,   m_file(0)
     ,   m_availableAudioInputDevices
             (QAudioDeviceInfo::availableDevices(QAudio::AudioInput))
     ,   m_audioInputDevice(QAudioDeviceInfo::defaultInputDevice())
     ,   m_audioInput(0)
     ,   m_audioInputIODevice(0)
     ,   m_recordPosition(0)
     ,   m_availableAudioOutputDevices
             (QAudioDeviceInfo::availableDevices(QAudio::AudioOutput))
     ,   m_audioOutputDevice(QAudioDeviceInfo::defaultOutputDevice())
     ,   m_audioOutput(0)
     ,   m_playPosition(0)
     ,   m_dataLength(0)
     ,   m_rmsLevel(0.0)
     ,   m_peakLevel(0.0)
     ,   m_spectrumLengthBytes(0)
     ,   m_spectrumAnalyser()
     ,   m_spectrumPosition(0)
     ,   m_count(0)
 {
     qRegisterMetaType<FrequencySpectrum>("FrequencySpectrum");
     CHECKED_CONNECT(&m_spectrumAnalyser,
                     SIGNAL(spectrumChanged(FrequencySpectrum)),
                     this,
                     SLOT(spectrumChanged(FrequencySpectrum)));

     initialize();

 #ifdef DUMP_DATA
     createOutputDir();
 #endif

 #ifdef DUMP_SPECTRUM
     m_spectrumAnalyser.setOutputPath(outputPath());
 #endif
 }

 Engine::~Engine()
 {

 }

 //-----------------------------------------------------------------------------
 // Public functions
 //-----------------------------------------------------------------------------

 bool Engine::loadFile(const QString &fileName)
 {
     bool result = false;
     m_generateTone = false;

     Q_ASSERT(!fileName.isEmpty());
     Q_ASSERT(!m_file);
     m_file = new QFile(fileName, this);
     m_file->setFileName(fileName);
     Q_ASSERT(m_file->exists());
     if (m_file->open(QFile::ReadOnly)) {
         m_wavFile.readHeader(*m_file);
         if (isPCMS16LE(m_wavFile.format())) {
             result = initialize();
         } else {
             emit errorMessage(tr("Audio format not supported"),
                               formatToString(m_wavFile.format()));
         }
     } else {
         emit errorMessage(tr("Could not open file"), fileName);
     }

     delete m_file;
     m_file = 0;

     return result;
 }

 bool Engine::generateTone(const Tone &tone)
 {
     Q_ASSERT(!m_file);
     m_generateTone = true;
     m_tone = tone;
     ENGINE_DEBUG << "Engine::generateTone"
                  << "startFreq" << m_tone.startFreq
                  << "endFreq" << m_tone.endFreq
                  << "amp" << m_tone.amplitude;
     return initialize();
 }

 bool Engine::generateSweptTone(qreal amplitude)
 {
     Q_ASSERT(!m_file);
     m_generateTone = true;
     m_tone.startFreq = 1;
     m_tone.endFreq = 0;
     m_tone.amplitude = amplitude;
     ENGINE_DEBUG << "Engine::generateSweptTone"
                  << "startFreq" << m_tone.startFreq
                  << "amp" << m_tone.amplitude;
     return initialize();
 }

 bool Engine::initializeRecord()
 {
     ENGINE_DEBUG << "Engine::initializeRecord";
     Q_ASSERT(!m_file);
     m_generateTone = false;
     m_tone = SweptTone();
     return initialize();
 }

 qint64 Engine::bufferDuration() const
 {
     return BufferDurationUs;
 }

 qint64 Engine::dataDuration() const
 {
     qint64 result = 0;
     if (QAudioFormat() != m_format)
         result = audioDuration(m_format, m_dataLength);
     return result;
 }

 qint64 Engine::audioBufferLength() const
 {
     qint64 length = 0;
     if (QAudio::ActiveState == m_state || QAudio::IdleState == m_state) {
         Q_ASSERT(QAudioFormat() != m_format);
         switch (m_mode) {
         case QAudio::AudioInput:
             length = m_audioInput->bufferSize();
             break;
         case QAudio::AudioOutput:
             length = m_audioOutput->bufferSize();
             break;
         }
     }
     return length;
 }

 void Engine::setWindowFunction(WindowFunction type)
 {
     m_spectrumAnalyser.setWindowFunction(type);
 }

 //-----------------------------------------------------------------------------
 // Public slots
 //-----------------------------------------------------------------------------

 void Engine::startRecording()
 {
     if (m_audioInput) {
         if (QAudio::AudioInput == m_mode &&
             QAudio::SuspendedState == m_state) {
             m_audioInput->resume();
         } else {
             m_spectrumAnalyser.cancelCalculation();
             spectrumChanged(0, 0, FrequencySpectrum());

             m_buffer.fill(0);
             setRecordPosition(0, true);
             stopPlayback();
             m_mode = QAudio::AudioInput;
             CHECKED_CONNECT(m_audioInput, SIGNAL(stateChanged(QAudio::State)),
                             this, SLOT(audioStateChanged(QAudio::State)));
             CHECKED_CONNECT(m_audioInput, SIGNAL(notify()),
                             this, SLOT(audioNotify()));
             m_count = 0;
             m_dataLength = 0;
             emit dataDurationChanged(0);
             m_audioInputIODevice = m_audioInput->start();
             CHECKED_CONNECT(m_audioInputIODevice, SIGNAL(readyRead()),
                             this, SLOT(audioDataReady()));
         }
     }
 }

 void Engine::startPlayback()
 {
     if (m_audioOutput) {
         if (QAudio::AudioOutput == m_mode &&
             QAudio::SuspendedState == m_state) {
 #ifdef Q_OS_WIN
             // The Windows backend seems to internally go back into ActiveState
             // while still returning SuspendedState, so to ensure that it doesn't
             // ignore the resume() call, we first re-suspend
             m_audioOutput->suspend();
 #endif
             m_audioOutput->resume();
         } else {
             m_spectrumAnalyser.cancelCalculation();
             spectrumChanged(0, 0, FrequencySpectrum());

             setPlayPosition(0, true);
             stopRecording();
             m_mode = QAudio::AudioOutput;
             CHECKED_CONNECT(m_audioOutput, SIGNAL(stateChanged(QAudio::State)),
                             this, SLOT(audioStateChanged(QAudio::State)));
             CHECKED_CONNECT(m_audioOutput, SIGNAL(notify()),
                             this, SLOT(audioNotify()));
             m_count = 0;
             m_audioOutputIODevice.close();
             m_audioOutputIODevice.setBuffer(&m_buffer);
             m_audioOutputIODevice.open(QIODevice::ReadOnly);
             m_audioOutput->start(&m_audioOutputIODevice);
         }
     }
 }

 void Engine::suspend()
 {
     if (QAudio::ActiveState == m_state ||
         QAudio::IdleState == m_state) {
         switch (m_mode) {
         case QAudio::AudioInput:
             m_audioInput->suspend();
             break;
         case QAudio::AudioOutput:
             m_audioOutput->suspend();
             break;
         }
     }
 }

 void Engine::setAudioInputDevice(const QAudioDeviceInfo &device)
 {
     if (device.deviceName() != m_audioInputDevice.deviceName()) {
         m_audioInputDevice = device;
         initialize();
     }
 }

 void Engine::setAudioOutputDevice(const QAudioDeviceInfo &device)
 {
     if (device.deviceName() != m_audioOutputDevice.deviceName()) {
         m_audioOutputDevice = device;
         initialize();
     }
 }

 //-----------------------------------------------------------------------------
 // Private slots
 //-----------------------------------------------------------------------------

 void Engine::audioNotify()
 {
     switch (m_mode) {
     case QAudio::AudioInput: {
             const qint64 recordPosition =
                     qMin(BufferDurationUs, m_audioInput->processedUSecs());
             setRecordPosition(recordPosition);

             // Calculate level of most recently captured data
             qint64 levelLength = audioLength(m_format, LevelWindowUs);
             levelLength = qMin(m_dataLength, levelLength);
             const qint64 levelPosition = m_dataLength - levelLength;
             calculateLevel(levelPosition, levelLength);

             // Calculate spectrum of most recently captured data
             if (m_dataLength >= m_spectrumLengthBytes) {
                 const qint64 spectrumPosition = m_dataLength - m_spectrumLengthBytes;
                 calculateSpectrum(spectrumPosition);
             }
         }
         break;
     case QAudio::AudioOutput: {
             const qint64 playPosition =
                     qMin(dataDuration(), m_audioOutput->processedUSecs());
             setPlayPosition(playPosition);

             qint64 analysisPosition = audioLength(m_format, playPosition);

             // Calculate level of data starting at current playback position
             const qint64 levelLength = audioLength(m_format, LevelWindowUs);
             if (analysisPosition + levelLength < m_dataLength)
                 calculateLevel(analysisPosition, levelLength);

             if (analysisPosition + m_spectrumLengthBytes < m_dataLength)
                 calculateSpectrum(analysisPosition);

             if (dataDuration() == playPosition)
                 stopPlayback();
         }
         break;
     }
 }

 void Engine::audioStateChanged(QAudio::State state)
 {
     ENGINE_DEBUG << "Engine::audioStateChanged from" << m_state
                  << "to" << state;

     if (QAudio::StoppedState == state) {
         // Check error
         QAudio::Error error = QAudio::NoError;
         switch (m_mode) {
         case QAudio::AudioInput:
             error = m_audioInput->error();
             break;
         case QAudio::AudioOutput:
             error = m_audioOutput->error();
             break;
         }
         if (QAudio::NoError != error) {
             reset();
             return;
         }
     }
     setState(state);
 }

 void Engine::audioDataReady()
 {
     const qint64 bytesReady = m_audioInput->bytesReady();
     const qint64 bytesSpace = m_buffer.size() - m_dataLength;
     const qint64 bytesToRead = qMin(bytesReady, bytesSpace);

     const qint64 bytesRead = m_audioInputIODevice->read(
                                        m_buffer.data() + m_dataLength,
                                        bytesToRead);

     if (bytesRead) {
         m_dataLength += bytesRead;

         const qint64 duration = audioDuration(m_format, m_dataLength);
         emit dataDurationChanged(duration);
     }

     if (m_buffer.size() == m_dataLength)
         stopRecording();
 }

 void Engine::spectrumChanged(const FrequencySpectrum &spectrum)
 {
     ENGINE_DEBUG << "Engine::spectrumChanged" << "pos" << m_spectrumPosition;
     const qint64 positionUs = audioDuration(m_format, m_spectrumPosition);
     const qint64 lengthUs = audioDuration(m_format, m_spectrumLengthBytes);
     emit spectrumChanged(positionUs, lengthUs, spectrum);
 }

 //-----------------------------------------------------------------------------
 // Private functions
 //-----------------------------------------------------------------------------

 void Engine::reset()
 {
     stopRecording();
     stopPlayback();
     setState(QAudio::AudioInput, QAudio::StoppedState);
     setFormat(QAudioFormat());
     delete m_audioInput;
     m_audioInput = 0;
     m_audioInputIODevice = 0;
     setRecordPosition(0);
     delete m_audioOutput;
     m_audioOutput = 0;
     setPlayPosition(0);
     m_buffer.clear();
     m_dataLength = 0;
     m_spectrumPosition = 0;
     emit dataDurationChanged(0);
     setLevel(0.0, 0.0, 0);
 }

 bool Engine::initialize()
 {
     bool result = false;

     reset();

     if (selectFormat()) {
         const qint64 bufferLength = audioLength(m_format, BufferDurationUs);
         m_buffer.resize(bufferLength);
         m_buffer.fill(0);
         emit bufferDurationChanged(BufferDurationUs);

         if (m_generateTone) {
             if (0 == m_tone.endFreq) {
                 const qreal nyquist = nyquistFrequency(m_format);
                 m_tone.endFreq = qMin(qreal(SpectrumHighFreq), nyquist);
             }

             // Call function defined in utils.h, at global scope
             ::generateTone(m_tone, m_format, m_buffer);
             m_dataLength = m_buffer.size();
             emit dataDurationChanged(bufferDuration());
             setRecordPosition(bufferDuration());
             result = true;
         } else if (m_file) {
             const qint64 length = m_wavFile.readData(*m_file, m_buffer, m_format);
             if (length) {
                 m_dataLength = length;
                 emit dataDurationChanged(dataDuration());
                 setRecordPosition(dataDuration());
                 result = true;
             }
         } else {
             m_audioInput = new QAudioInput(m_audioInputDevice, m_format, this);
             m_audioInput->setNotifyInterval(NotifyIntervalMs);
             result = true;
         }

         m_audioOutput = new QAudioOutput(m_audioOutputDevice, m_format, this);
         m_audioOutput->setNotifyInterval(NotifyIntervalMs);
         m_spectrumLengthBytes = SpectrumLengthSamples *
                                 (m_format.sampleSize() / 8) * m_format.channels();
     } else {
         if (m_file)
             emit errorMessage(tr("Audio format not supported"),
                               formatToString(m_format));
         else if (m_generateTone)
             emit errorMessage(tr("No suitable format found"), "");
         else
             emit errorMessage(tr("No common input / output format found"), "");
     }

     ENGINE_DEBUG << "Engine::initialize" << "format" << m_format;

     return result;
 }

 bool Engine::selectFormat()
 {
     bool foundSupportedFormat = false;

     if (m_file) {
         // Header is read from the WAV file; just need to check whether
         // it is supported by the audio output device
         QAudioFormat format = m_wavFile.format();
         if (m_audioOutputDevice.isFormatSupported(m_wavFile.format())) {
             setFormat(m_wavFile.format());
             foundSupportedFormat = true;
         } else {
             // Try flipping mono <-> stereo
             const int channels = (format.channels() == 1) ? 2 : 1;
             format.setChannels(channels);
             if (m_audioOutputDevice.isFormatSupported(format)) {
                 setFormat(format);
                 foundSupportedFormat = true;
             }
         }
     } else {

         QList<int> frequenciesList;
     #ifdef Q_OS_WIN
         // The Windows audio backend does not correctly report format support
         // (see QTBUG-9100).  Furthermore, although the audio subsystem captures
         // at 11025Hz, the resulting audio is corrupted.
         frequenciesList += 8000;
     #endif

         if (!m_generateTone)
             frequenciesList += m_audioInputDevice.supportedFrequencies();

         frequenciesList += m_audioOutputDevice.supportedFrequencies();
         frequenciesList = frequenciesList.toSet().toList(); // remove duplicates
         qSort(frequenciesList);
         ENGINE_DEBUG << "Engine::initialize frequenciesList" << frequenciesList;

         QList<int> channelsList;
         channelsList += m_audioInputDevice.supportedChannels();
         channelsList += m_audioOutputDevice.supportedChannels();
         channelsList = channelsList.toSet().toList();
         qSort(channelsList);
         ENGINE_DEBUG << "Engine::initialize channelsList" << channelsList;

         QAudioFormat format;
         format.setByteOrder(QAudioFormat::LittleEndian);
         format.setCodec("audio/pcm");
         format.setSampleSize(16);
         format.setSampleType(QAudioFormat::SignedInt);
         int frequency, channels;
         foreach (frequency, frequenciesList) {
             if (foundSupportedFormat)
                 break;
             format.setFrequency(frequency);
             foreach (channels, channelsList) {
                 format.setChannels(channels);
                 const bool inputSupport = m_generateTone ||
                                           m_audioInputDevice.isFormatSupported(format);
                 const bool outputSupport = m_audioOutputDevice.isFormatSupported(format);
                 ENGINE_DEBUG << "Engine::initialize checking " << format
                              << "input" << inputSupport
                              << "output" << outputSupport;
                 if (inputSupport && outputSupport) {
                     foundSupportedFormat = true;
                     break;
                 }
             }
         }

         if (!foundSupportedFormat)
             format = QAudioFormat();

         setFormat(format);
     }

     return foundSupportedFormat;
 }

 void Engine::stopRecording()
 {
     if (m_audioInput) {
         m_audioInput->stop();
         QCoreApplication::instance()->processEvents();
         m_audioInput->disconnect();
     }
     m_audioInputIODevice = 0;

 #ifdef DUMP_AUDIO
     dumpData();
 #endif
 }

 void Engine::stopPlayback()
 {
     if (m_audioOutput) {
         m_audioOutput->stop();
         QCoreApplication::instance()->processEvents();
         m_audioOutput->disconnect();
         setPlayPosition(0);
     }
 }

 void Engine::setState(QAudio::State state)
 {
     const bool changed = (m_state != state);
     m_state = state;
     if (changed)
         emit stateChanged(m_mode, m_state);
 }

 void Engine::setState(QAudio::Mode mode, QAudio::State state)
 {
     const bool changed = (m_mode != mode || m_state != state);
     m_mode = mode;
     m_state = state;
     if (changed)
         emit stateChanged(m_mode, m_state);
 }

 void Engine::setRecordPosition(qint64 position, bool forceEmit)
 {
     const bool changed = (m_recordPosition != position);
     m_recordPosition = position;
     if (changed || forceEmit)
         emit recordPositionChanged(m_recordPosition);
 }

 void Engine::setPlayPosition(qint64 position, bool forceEmit)
 {
     const bool changed = (m_playPosition != position);
     m_playPosition = position;
     if (changed || forceEmit)
         emit playPositionChanged(m_playPosition);
 }

 void Engine::calculateLevel(qint64 position, qint64 length)
 {
 #ifdef DISABLE_LEVEL
     Q_UNUSED(position)
     Q_UNUSED(length)
 #else
     Q_ASSERT(position + length <= m_dataLength);

     qreal peakLevel = 0.0;

     qreal sum = 0.0;
     const char *ptr = m_buffer.constData() + position;
     const char *const end = ptr + length;
     while (ptr < end) {
         const qint16 value = *reinterpret_cast<const qint16*>(ptr);
         const qreal fracValue = pcmToReal(value);
         peakLevel = qMax(peakLevel, fracValue);
         sum += fracValue * fracValue;
         ptr += 2;
     }
     const int numSamples = length / 2;
     qreal rmsLevel = sqrt(sum / numSamples);

     rmsLevel = qMax(qreal(0.0), rmsLevel);
     rmsLevel = qMin(qreal(1.0), rmsLevel);
     setLevel(rmsLevel, peakLevel, numSamples);

     ENGINE_DEBUG << "Engine::calculateLevel" << "pos" << position << "len" << length
                  << "rms" << rmsLevel << "peak" << peakLevel;
 #endif
 }

 void Engine::calculateSpectrum(qint64 position)
 {
 #ifdef DISABLE_SPECTRUM
     Q_UNUSED(position)
 #else
     Q_ASSERT(position + m_spectrumLengthBytes <= m_dataLength);
     Q_ASSERT(0 == m_spectrumLengthBytes % 2); // constraint of FFT algorithm

     // QThread::currentThread is marked 'for internal use only', but
     // we're only using it for debug output here, so it's probably OK :)
     ENGINE_DEBUG << "Engine::calculateSpectrum" << QThread::currentThread()
                  << "count" << m_count << "pos" << position << "len" << m_spectrumLengthBytes
                  << "spectrumAnalyser.isReady" << m_spectrumAnalyser.isReady();

     if(m_spectrumAnalyser.isReady()) {
         m_spectrumBuffer = QByteArray::fromRawData(m_buffer.constData() + position,
                                                    m_spectrumLengthBytes);
         m_spectrumPosition = position;
         m_spectrumAnalyser.calculate(m_spectrumBuffer, m_format);
     }
 #endif
 }

 void Engine::setFormat(const QAudioFormat &format)
 {
     const bool changed = (format != m_format);
     m_format = format;
     if (changed)
         emit formatChanged(m_format);
 }

 void Engine::setLevel(qreal rmsLevel, qreal peakLevel, int numSamples)
 {
     m_rmsLevel = rmsLevel;
     m_peakLevel = peakLevel;
     emit levelChanged(m_rmsLevel, m_peakLevel, numSamples);
 }

 #ifdef DUMP_DATA
 void Engine::createOutputDir()
 {
     m_outputDir.setPath("output");

     // Ensure output directory exists and is empty
     if (m_outputDir.exists()) {
         const QStringList files = m_outputDir.entryList(QDir::Files);
         QString file;
         foreach (file, files)
             m_outputDir.remove(file);
     } else {
         QDir::current().mkdir("output");
     }
 }
 #endif // DUMP_DATA

 #ifdef DUMP_AUDIO
 void Engine::dumpData()
 {
     const QString txtFileName = m_outputDir.filePath("data.txt");
     QFile txtFile(txtFileName);
     txtFile.open(QFile::WriteOnly | QFile::Text);
     QTextStream stream(&txtFile);
     const qint16 *ptr = reinterpret_cast<const qint16*>(m_buffer.constData());
     const int numSamples = m_dataLength / (2 * m_format.channels());
     for (int i=0; i<numSamples; ++i) {
         stream << i << "\t" << *ptr << "\n";
         ptr += m_format.channels();
     }

     const QString pcmFileName = m_outputDir.filePath("data.pcm");
     QFile pcmFile(pcmFileName);
     pcmFile.open(QFile::WriteOnly);
     pcmFile.write(m_buffer.constData(), m_dataLength);
 }
 #endif // DUMP_AUDIO
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