Qt 5.11 | Qt Multimedia | Audio Input Example | audioinput.cpp Example File

Qt 5.11.3 Reference Documentation

# audioinput.cpp Example File

multimedia/audioinput/audioinput.cpp

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      #include "audioinput.h"

      #include <stdlib.h>
      #include <math.h>

      #include <QDateTime>
      #include <QDebug>
      #include <QPainter>
      #include <QVBoxLayout>
      #include <QAudioDeviceInfo>
      #include <QAudioInput>
      #include <qendian.h>

      AudioInfo::AudioInfo(const QAudioFormat &format)
          : m_format(format)
      {
          switch (m_format.sampleSize()) {
          case 8:
              switch (m_format.sampleType()) {
              case QAudioFormat::UnSignedInt:
                  m_maxAmplitude = 255;
                  break;
              case QAudioFormat::SignedInt:
                  m_maxAmplitude = 127;
                  break;
              default:
                  break;
              }
              break;
          case 16:
              switch (m_format.sampleType()) {
              case QAudioFormat::UnSignedInt:
                  m_maxAmplitude = 65535;
                  break;
              case QAudioFormat::SignedInt:
                  m_maxAmplitude = 32767;
                  break;
              default:
                  break;
              }
              break;

          case 32:
              switch (m_format.sampleType()) {
              case QAudioFormat::UnSignedInt:
                  m_maxAmplitude = 0xffffffff;
                  break;
              case QAudioFormat::SignedInt:
                  m_maxAmplitude = 0x7fffffff;
                  break;
              case QAudioFormat::Float:
                  m_maxAmplitude = 0x7fffffff; // Kind of
              default:
                  break;
              }
              break;

          default:
              break;
          }
      }

      void AudioInfo::start()
      {
          open(QIODevice::WriteOnly);
      }

      void AudioInfo::stop()
      {
          close();
      }

      qint64 AudioInfo::readData(char *data, qint64 maxlen)
      {
          Q_UNUSED(data)
          Q_UNUSED(maxlen)

          return 0;
      }

      qint64 AudioInfo::writeData(const char *data, qint64 len)
      {
          if (m_maxAmplitude) {
              Q_ASSERT(m_format.sampleSize() % 8 == 0);
              const int channelBytes = m_format.sampleSize() / 8;
              const int sampleBytes = m_format.channelCount() * channelBytes;
              Q_ASSERT(len % sampleBytes == 0);
              const int numSamples = len / sampleBytes;

              quint32 maxValue = 0;
              const unsigned char *ptr = reinterpret_cast<const unsigned char *>(data);

              for (int i = 0; i < numSamples; ++i) {
                  for (int j = 0; j < m_format.channelCount(); ++j) {
                      quint32 value = 0;

                      if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                          value = *reinterpret_cast<const quint8*>(ptr);
                      } else if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::SignedInt) {
                          value = qAbs(*reinterpret_cast<const qint8*>(ptr));
                      } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                          if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                              value = qFromLittleEndian<quint16>(ptr);
                          else
                              value = qFromBigEndian<quint16>(ptr);
                      } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::SignedInt) {
                          if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                              value = qAbs(qFromLittleEndian<qint16>(ptr));
                          else
                              value = qAbs(qFromBigEndian<qint16>(ptr));
                      } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                          if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                              value = qFromLittleEndian<quint32>(ptr);
                          else
                              value = qFromBigEndian<quint32>(ptr);
                      } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::SignedInt) {
                          if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                              value = qAbs(qFromLittleEndian<qint32>(ptr));
                          else
                              value = qAbs(qFromBigEndian<qint32>(ptr));
                      } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::Float) {
                          value = qAbs(*reinterpret_cast<const float*>(ptr) * 0x7fffffff); // assumes 0-1.0
                      }

                      maxValue = qMax(value, maxValue);
                      ptr += channelBytes;
                  }
              }

              maxValue = qMin(maxValue, m_maxAmplitude);
              m_level = qreal(maxValue) / m_maxAmplitude;
          }

          emit update();
          return len;
      }

      RenderArea::RenderArea(QWidget *parent)
          : QWidget(parent)
      {
          setBackgroundRole(QPalette::Base);
          setAutoFillBackground(true);

          setMinimumHeight(30);
          setMinimumWidth(200);
      }

      void RenderArea::paintEvent(QPaintEvent * /* event */)
      {
          QPainter painter(this);

          painter.setPen(Qt::black);
          painter.drawRect(QRect(painter.viewport().left()+10,
                                 painter.viewport().top()+10,
                                 painter.viewport().right()-20,
                                 painter.viewport().bottom()-20));
          if (m_level == 0.0)
              return;

          int pos = ((painter.viewport().right()-20)-(painter.viewport().left()+11))*m_level;
          painter.fillRect(painter.viewport().left()+11,
                           painter.viewport().top()+10,
                           pos,
                           painter.viewport().height()-21,
                           Qt::red);
      }

      void RenderArea::setLevel(qreal value)
      {
          m_level = value;
          update();
      }

      InputTest::InputTest()
      {
          initializeWindow();
          initializeAudio(QAudioDeviceInfo::defaultInputDevice());
      }

      void InputTest::initializeWindow()
      {
          QWidget *window = new QWidget;
          QVBoxLayout *layout = new QVBoxLayout;

          m_canvas = new RenderArea(this);
          layout->addWidget(m_canvas);

          m_deviceBox = new QComboBox(this);
          const QAudioDeviceInfo &defaultDeviceInfo = QAudioDeviceInfo::defaultInputDevice();
          m_deviceBox->addItem(defaultDeviceInfo.deviceName(), qVariantFromValue(defaultDeviceInfo));
          for (auto &deviceInfo: QAudioDeviceInfo::availableDevices(QAudio::AudioInput)) {
              if (deviceInfo != defaultDeviceInfo)
                  m_deviceBox->addItem(deviceInfo.deviceName(), qVariantFromValue(deviceInfo));
          }

          connect(m_deviceBox, QOverload<int>::of(&QComboBox::activated), this, &InputTest::deviceChanged);
          layout->addWidget(m_deviceBox);

          m_volumeSlider = new QSlider(Qt::Horizontal, this);
          m_volumeSlider->setRange(0, 100);
          m_volumeSlider->setValue(100);
          connect(m_volumeSlider, &QSlider::valueChanged, this, &InputTest::sliderChanged);
          layout->addWidget(m_volumeSlider);

          m_modeButton = new QPushButton(this);
          connect(m_modeButton, &QPushButton::clicked, this, &InputTest::toggleMode);
          layout->addWidget(m_modeButton);

          m_suspendResumeButton = new QPushButton(this);
          connect(m_suspendResumeButton, &QPushButton::clicked, this, &InputTest::toggleSuspend);
          layout->addWidget(m_suspendResumeButton);

          window->setLayout(layout);

          setCentralWidget(window);
          window->show();
      }

      void InputTest::initializeAudio(const QAudioDeviceInfo &deviceInfo)
      {
          QAudioFormat format;
          format.setSampleRate(8000);
          format.setChannelCount(1);
          format.setSampleSize(16);
          format.setSampleType(QAudioFormat::SignedInt);
          format.setByteOrder(QAudioFormat::LittleEndian);
          format.setCodec("audio/pcm");

          if (!deviceInfo.isFormatSupported(format)) {
              qWarning() << "Default format not supported - trying to use nearest";
              format = deviceInfo.nearestFormat(format);
          }

          m_audioInfo.reset(new AudioInfo(format));
          connect(m_audioInfo.data(), &AudioInfo::update, [this]() {
              m_canvas->setLevel(m_audioInfo->level());
          });

          m_audioInput.reset(new QAudioInput(deviceInfo, format));
          qreal initialVolume = QAudio::convertVolume(m_audioInput->volume(),
                                                      QAudio::LinearVolumeScale,
                                                      QAudio::LogarithmicVolumeScale);
          m_volumeSlider->setValue(qRound(initialVolume * 100));
          m_audioInfo->start();
          toggleMode();
      }

      void InputTest::toggleMode()
      {
          m_audioInput->stop();
          toggleSuspend();

          // Change bewteen pull and push modes
          if (m_pullMode) {
              m_modeButton->setText(tr("Enable push mode"));
              m_audioInput->start(m_audioInfo.data());
          } else {
              m_modeButton->setText(tr("Enable pull mode"));
              auto io = m_audioInput->start();
              connect(io, &QIODevice::readyRead,
                  [&, io]() {
                      qint64 len = m_audioInput->bytesReady();
                      const int BufferSize = 4096;
                      if (len > BufferSize)
                          len = BufferSize;

                      QByteArray buffer(len, 0);
                      qint64 l = io->read(buffer.data(), len);
                      if (l > 0)
                          m_audioInfo->write(buffer.constData(), l);
                  });
          }

          m_pullMode = !m_pullMode;
      }

      void InputTest::toggleSuspend()
      {
          // toggle suspend/resume
          if (m_audioInput->state() == QAudio::SuspendedState || m_audioInput->state() == QAudio::StoppedState) {
              m_audioInput->resume();
              m_suspendResumeButton->setText(tr("Suspend recording"));
          } else if (m_audioInput->state() == QAudio::ActiveState) {
              m_audioInput->suspend();
              m_suspendResumeButton->setText(tr("Resume recording"));
          } else if (m_audioInput->state() == QAudio::IdleState) {
              // no-op
          }
      }

      void InputTest::deviceChanged(int index)
      {
          m_audioInfo->stop();
          m_audioInput->stop();
          m_audioInput->disconnect(this);

          initializeAudio(m_deviceBox->itemData(index).value<QAudioDeviceInfo>());
      }

      void InputTest::sliderChanged(int value)
      {
          qreal linearVolume = QAudio::convertVolume(value / qreal(100),
                                                     QAudio::LogarithmicVolumeScale,
                                                     QAudio::LinearVolumeScale);

          m_audioInput->setVolume(linearVolume);
      }