engine.cpp Example File | Qt Multimedia 5.12.7

Qt 5.12 | Qt Multimedia | Spectrum Example | engine.cpp Example File

Qt 5.12.7 Reference Documentation

# engine.cpp Example File

multimedia/spectrum/app/engine.cpp

      /****************************************************************************
      **
      ** Copyright (C) 2017 The Qt Company Ltd.
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the examples of the Qt Toolkit.
      **
      ** $QT_BEGIN_LICENSE:BSD$
      ** Commercial License Usage
      ** Licensees holding valid commercial Qt licenses may use this file in
      ** accordance with the commercial license agreement provided with the
      ** Software or, alternatively, in accordance with the terms contained in
      ** a written agreement between you and The Qt Company. For licensing terms
      ** and conditions see https://www.qt.io/terms-conditions. For further
      ** information use the contact form at https://www.qt.io/contact-us.
      **
      ** BSD License Usage
      ** Alternatively, you may use this file under the terms of the BSD license
      ** as follows:
      **
      ** "Redistribution and use in source and binary forms, with or without
      ** modification, are permitted provided that the following conditions are
      ** met:
      **   * Redistributions of source code must retain the above copyright
      **     notice, this list of conditions and the following disclaimer.
      **   * Redistributions in binary form must reproduce the above copyright
      **     notice, this list of conditions and the following disclaimer in
      **     the documentation and/or other materials provided with the
      **     distribution.
      **   * Neither the name of The Qt Company Ltd nor the names of its
      **     contributors may be used to endorse or promote products derived
      **     from this software without specific prior written permission.
      **
      **
      ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      #include "engine.h"
      #include "tonegenerator.h"
      #include "utils.h"

      #include <math.h>

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

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

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

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

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

      Engine::Engine(QObject *parent)
          :   QObject(parent)
          ,   m_mode(QAudio::AudioInput)
          ,   m_state(QAudio::StoppedState)
          ,   m_generateTone(false)
          ,   m_file(0)
          ,   m_analysisFile(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_bufferPosition(0)
          ,   m_bufferLength(0)
          ,   m_dataLength(0)
          ,   m_levelBufferLength(0)
          ,   m_rmsLevel(0.0)
          ,   m_peakLevel(0.0)
          ,   m_spectrumBufferLength(0)
          ,   m_spectrumAnalyser()
          ,   m_spectrumPosition(0)
          ,   m_count(0)
      {
          qRegisterMetaType<FrequencySpectrum>("FrequencySpectrum");
          qRegisterMetaType<WindowFunction>("WindowFunction");
          connect(&m_spectrumAnalyser, QOverload<const FrequencySpectrum&>::of(&SpectrumAnalyser::spectrumChanged),
                  this, QOverload<const FrequencySpectrum&>::of(&Engine::spectrumChanged));

          // This code might misinterpret things like "-something -category".  But
          // it's unlikely that that needs to be supported so we'll let it go.
          QStringList arguments = QCoreApplication::instance()->arguments();
          for (int i = 0; i < arguments.count(); ++i) {
              if (arguments.at(i) == QStringLiteral("--"))
                  break;

              if (arguments.at(i) == QStringLiteral("-category")
                      || arguments.at(i) == QStringLiteral("--category")) {
                  ++i;
                  if (i < arguments.count())
                      m_audioOutputCategory = arguments.at(i);
                  else
                      --i;
              }
          }

          initialize();

      #ifdef DUMP_DATA
          createOutputDir();
      #endif

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

      Engine::~Engine()
      {

      }

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

      bool Engine::loadFile(const QString &fileName)
      {
          reset();
          bool result = false;
          Q_ASSERT(!m_generateTone);
          Q_ASSERT(!m_file);
          Q_ASSERT(!fileName.isEmpty());
          m_file = new WavFile(this);
          if (m_file->open(fileName)) {
              if (isPCMS16LE(m_file->fileFormat())) {
                  result = initialize();
              } else {
                  emit errorMessage(tr("Audio format not supported"),
                                    formatToString(m_file->fileFormat()));
              }
          } else {
              emit errorMessage(tr("Could not open file"), fileName);
          }
          if (result) {
              m_analysisFile = new WavFile(this);
              m_analysisFile->open(fileName);
          }
          return result;
      }

      bool Engine::generateTone(const Tone &tone)
      {
          reset();
          Q_ASSERT(!m_generateTone);
          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_generateTone);
          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()
      {
          reset();
          ENGINE_DEBUG << "Engine::initializeRecord";
          Q_ASSERT(!m_generateTone);
          Q_ASSERT(!m_file);
          m_generateTone = false;
          m_tone = SweptTone();
          return initialize();
      }

      qint64 Engine::bufferLength() const
      {
          return m_file ? m_file->size() : m_bufferLength;
      }

      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;
                  connect(m_audioInput, &QAudioInput::stateChanged,
                          this, &Engine::audioStateChanged);
                  connect(m_audioInput, &QAudioInput::notify,
                          this, &Engine::audioNotify);

                  m_count = 0;
                  m_dataLength = 0;
                  emit dataLengthChanged(0);
                  m_audioInputIODevice = m_audioInput->start();
                  connect(m_audioInputIODevice, &QIODevice::readyRead,
                          this, &Engine::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;
                  connect(m_audioOutput, &QAudioOutput::stateChanged,
                          this, &Engine::audioStateChanged);
                  connect(m_audioOutput, &QAudioOutput::notify,
                          this, &Engine::audioNotify);

                  m_count = 0;
                  if (m_file) {
                      m_file->seek(0);
                      m_bufferPosition = 0;
                      m_dataLength = 0;
                      m_audioOutput->start(m_file);
                  } else {
                      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(m_bufferLength, audioLength(m_format, m_audioInput->processedUSecs()));
                  setRecordPosition(recordPosition);
                  const qint64 levelPosition = m_dataLength - m_levelBufferLength;
                  if (levelPosition >= 0)
                      calculateLevel(levelPosition, m_levelBufferLength);
                  if (m_dataLength >= m_spectrumBufferLength) {
                      const qint64 spectrumPosition = m_dataLength - m_spectrumBufferLength;
                      calculateSpectrum(spectrumPosition);
                  }
                  emit bufferChanged(0, m_dataLength, m_buffer);
              }
              break;
          case QAudio::AudioOutput: {
                  const qint64 playPosition = audioLength(m_format, m_audioOutput->processedUSecs());
                  setPlayPosition(qMin(bufferLength(), playPosition));
                  const qint64 levelPosition = playPosition - m_levelBufferLength;
                  const qint64 spectrumPosition = playPosition - m_spectrumBufferLength;
                  if (m_file) {
                      if (levelPosition > m_bufferPosition ||
                          spectrumPosition > m_bufferPosition ||
                          qMax(m_levelBufferLength, m_spectrumBufferLength) > m_dataLength) {
                          m_bufferPosition = 0;
                          m_dataLength = 0;
                          // Data needs to be read into m_buffer in order to be analysed
                          const qint64 readPos = qMax(qint64(0), qMin(levelPosition, spectrumPosition));
                          const qint64 readEnd = qMin(m_analysisFile->size(), qMax(levelPosition + m_levelBufferLength, spectrumPosition + m_spectrumBufferLength));
                          const qint64 readLen = readEnd - readPos + audioLength(m_format, WaveformWindowDuration);
                          qDebug() << "Engine::audioNotify [1]"
                                   << "analysisFileSize" << m_analysisFile->size()
                                   << "readPos" << readPos
                                   << "readLen" << readLen;
                          if (m_analysisFile->seek(readPos + m_analysisFile->headerLength())) {
                              m_buffer.resize(readLen);
                              m_bufferPosition = readPos;
                              m_dataLength = m_analysisFile->read(m_buffer.data(), readLen);
                              qDebug() << "Engine::audioNotify [2]" << "bufferPosition" << m_bufferPosition << "dataLength" << m_dataLength;
                          } else {
                              qDebug() << "Engine::audioNotify [2]" << "file seek error";
                          }
                          emit bufferChanged(m_bufferPosition, m_dataLength, m_buffer);
                      }
                  } else {
                      if (playPosition >= m_dataLength)
                          stopPlayback();
                  }
                  if (levelPosition >= 0 && levelPosition + m_levelBufferLength < m_bufferPosition + m_dataLength)
                      calculateLevel(levelPosition, m_levelBufferLength);
                  if (spectrumPosition >= 0 && spectrumPosition + m_spectrumBufferLength < m_bufferPosition + m_dataLength)
                      calculateSpectrum(spectrumPosition);
              }
              break;
          }
      }

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

          if (QAudio::IdleState == state && m_file && m_file->pos() == m_file->size()) {
              stopPlayback();
          } else {
              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()
      {
          Q_ASSERT(0 == m_bufferPosition);
          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;
              emit dataLengthChanged(dataLength());
          }

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

      void Engine::spectrumChanged(const FrequencySpectrum &spectrum)
      {
          ENGINE_DEBUG << "Engine::spectrumChanged" << "pos" << m_spectrumPosition;
          emit spectrumChanged(m_spectrumPosition, m_spectrumBufferLength, spectrum);
      }

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

      void Engine::resetAudioDevices()
      {
          delete m_audioInput;
          m_audioInput = 0;
          m_audioInputIODevice = 0;
          setRecordPosition(0);
          delete m_audioOutput;
          m_audioOutput = 0;
          setPlayPosition(0);
          m_spectrumPosition = 0;
          setLevel(0.0, 0.0, 0);
      }

      void Engine::reset()
      {
          stopRecording();
          stopPlayback();
          setState(QAudio::AudioInput, QAudio::StoppedState);
          setFormat(QAudioFormat());
          m_generateTone = false;
          delete m_file;
          m_file = 0;
          delete m_analysisFile;
          m_analysisFile = 0;
          m_buffer.clear();
          m_bufferPosition = 0;
          m_bufferLength = 0;
          m_dataLength = 0;
          emit dataLengthChanged(0);
          resetAudioDevices();
      }

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

          QAudioFormat format = m_format;

          if (selectFormat()) {
              if (m_format != format) {
                  resetAudioDevices();
                  if (m_file) {
                      emit bufferLengthChanged(bufferLength());
                      emit dataLengthChanged(dataLength());
                      emit bufferChanged(0, 0, m_buffer);
                      setRecordPosition(bufferLength());
                      result = true;
                  } else {
                      m_bufferLength = audioLength(m_format, BufferDurationUs);
                      m_buffer.resize(m_bufferLength);
                      m_buffer.fill(0);
                      emit bufferLengthChanged(bufferLength());
                      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_bufferLength;
                          emit dataLengthChanged(dataLength());
                          emit bufferChanged(0, m_dataLength, m_buffer);
                          setRecordPosition(m_bufferLength);
                          result = true;
                      } else {
                          emit bufferChanged(0, 0, m_buffer);
                          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_audioOutput->setCategory(m_audioOutputCategory);
              }
          } 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" << "m_bufferLength" << m_bufferLength;
          ENGINE_DEBUG << "Engine::initialize" << "m_dataLength" << m_dataLength;
          ENGINE_DEBUG << "Engine::initialize" << "format" << m_format;
          ENGINE_DEBUG << "Engine::initialize" << "m_audioOutputCategory" << m_audioOutputCategory;

          return result;
      }

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

          if (m_file || QAudioFormat() != m_format) {
              QAudioFormat format = m_format;
              if (m_file)
                  // Header is read from the WAV file; just need to check whether
                  // it is supported by the audio output device
                  format = m_file->fileFormat();
              if (m_audioOutputDevice.isFormatSupported(format)) {
                  setFormat(format);
                  foundSupportedFormat = true;
              }
          } else {

              QList<int> sampleRatesList;
          #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.
              sampleRatesList += 8000;
          #endif

              if (!m_generateTone)
                  sampleRatesList += m_audioInputDevice.supportedSampleRates();

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

              QList<int> channelsList;
              channelsList += m_audioInputDevice.supportedChannelCounts();
              channelsList += m_audioOutputDevice.supportedChannelCounts();
              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 sampleRate, channels;
              foreach (sampleRate, sampleRatesList) {
                  if (foundSupportedFormat)
                      break;
                  format.setSampleRate(sampleRate);
                  foreach (channels, channelsList) {
                      format.setChannelCount(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_bufferPosition + m_dataLength);

          qreal peakLevel = 0.0;

          qreal sum = 0.0;
          const char *ptr = m_buffer.constData() + position - m_bufferPosition;
          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_spectrumBufferLength <= m_bufferPosition + m_dataLength);
          Q_ASSERT(0 == m_spectrumBufferLength % 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_spectrumBufferLength
                       << "spectrumAnalyser.isReady" << m_spectrumAnalyser.isReady();

          if (m_spectrumAnalyser.isReady()) {
              m_spectrumBuffer = QByteArray::fromRawData(m_buffer.constData() + position - m_bufferPosition,
                                                         m_spectrumBufferLength);
              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;
          m_levelBufferLength = audioLength(m_format, LevelWindowUs);
          m_spectrumBufferLength = SpectrumLengthSamples *
                                  (m_format.sampleSize() / 8) * m_format.channelCount();
          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