audiorecorder.cpp Example File

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  #include <QAudioProbe>
  #include <QAudioRecorder>
  #include <QDir>
  #include <QFileDialog>
  #include <QMediaRecorder>

  #include "audiorecorder.h"
  #include "qaudiolevel.h"

  #include "ui_audiorecorder.h"

  static qreal getPeakValue(const QAudioFormat &format);
  static QVector<qreal> getBufferLevels(const QAudioBuffer &buffer);

  template <class T>
  static QVector<qreal> getBufferLevels(const T *buffer, int frames, int channels);

  AudioRecorder::AudioRecorder(QWidget *parent) :
      QMainWindow(parent),
      ui(new Ui::AudioRecorder),
      outputLocationSet(false)
  {
      ui->setupUi(this);

      audioRecorder = new QAudioRecorder(this);
      probe = new QAudioProbe;
      connect(probe, SIGNAL(audioBufferProbed(QAudioBuffer)),
              this, SLOT(processBuffer(QAudioBuffer)));
      probe->setSource(audioRecorder);

      //audio devices
      ui->audioDeviceBox->addItem(tr("Default"), QVariant(QString()));
      foreach (const QString &device, audioRecorder->audioInputs()) {
          ui->audioDeviceBox->addItem(device, QVariant(device));
      }

      //audio codecs
      ui->audioCodecBox->addItem(tr("Default"), QVariant(QString()));
      foreach (const QString &codecName, audioRecorder->supportedAudioCodecs()) {
          ui->audioCodecBox->addItem(codecName, QVariant(codecName));
      }

      //containers
      ui->containerBox->addItem(tr("Default"), QVariant(QString()));
      foreach (const QString &containerName, audioRecorder->supportedContainers()) {
          ui->containerBox->addItem(containerName, QVariant(containerName));
      }

      //sample rate
      ui->sampleRateBox->addItem(tr("Default"), QVariant(0));
      foreach (int sampleRate, audioRecorder->supportedAudioSampleRates()) {
          ui->sampleRateBox->addItem(QString::number(sampleRate), QVariant(
                  sampleRate));
      }

      //channels
      ui->channelsBox->addItem(tr("Default"), QVariant(-1));
      ui->channelsBox->addItem(QStringLiteral("1"), QVariant(1));
      ui->channelsBox->addItem(QStringLiteral("2"), QVariant(2));
      ui->channelsBox->addItem(QStringLiteral("4"), QVariant(4));

      //quality
      ui->qualitySlider->setRange(0, int(QMultimedia::VeryHighQuality));
      ui->qualitySlider->setValue(int(QMultimedia::NormalQuality));

      //bitrates:
      ui->bitrateBox->addItem(tr("Default"), QVariant(0));
      ui->bitrateBox->addItem(QStringLiteral("32000"), QVariant(32000));
      ui->bitrateBox->addItem(QStringLiteral("64000"), QVariant(64000));
      ui->bitrateBox->addItem(QStringLiteral("96000"), QVariant(96000));
      ui->bitrateBox->addItem(QStringLiteral("128000"), QVariant(128000));

      connect(audioRecorder, SIGNAL(durationChanged(qint64)), this,
              SLOT(updateProgress(qint64)));
      connect(audioRecorder, SIGNAL(statusChanged(QMediaRecorder::Status)), this,
              SLOT(updateStatus(QMediaRecorder::Status)));
      connect(audioRecorder, SIGNAL(stateChanged(QMediaRecorder::State)),
              this, SLOT(onStateChanged(QMediaRecorder::State)));
      connect(audioRecorder, SIGNAL(error(QMediaRecorder::Error)), this,
              SLOT(displayErrorMessage()));
  }

  AudioRecorder::~AudioRecorder()
  {
      delete audioRecorder;
      delete probe;
  }

  void AudioRecorder::updateProgress(qint64 duration)
  {
      if (audioRecorder->error() != QMediaRecorder::NoError || duration < 2000)
          return;

      ui->statusbar->showMessage(tr("Recorded %1 sec").arg(duration / 1000));
  }

  void AudioRecorder::updateStatus(QMediaRecorder::Status status)
  {
      QString statusMessage;

      switch (status) {
      case QMediaRecorder::RecordingStatus:
          statusMessage = tr("Recording to %1").arg(audioRecorder->actualLocation().toString());
          break;
      case QMediaRecorder::PausedStatus:
          clearAudioLevels();
          statusMessage = tr("Paused");
          break;
      case QMediaRecorder::UnloadedStatus:
      case QMediaRecorder::LoadedStatus:
          clearAudioLevels();
          statusMessage = tr("Stopped");
      default:
          break;
      }

      if (audioRecorder->error() == QMediaRecorder::NoError)
          ui->statusbar->showMessage(statusMessage);
  }

  void AudioRecorder::onStateChanged(QMediaRecorder::State state)
  {
      switch (state) {
      case QMediaRecorder::RecordingState:
          ui->recordButton->setText(tr("Stop"));
          ui->pauseButton->setText(tr("Pause"));
          break;
      case QMediaRecorder::PausedState:
          ui->recordButton->setText(tr("Stop"));
          ui->pauseButton->setText(tr("Resume"));
          break;
      case QMediaRecorder::StoppedState:
          ui->recordButton->setText(tr("Record"));
          ui->pauseButton->setText(tr("Pause"));
          break;
      }

      ui->pauseButton->setEnabled(audioRecorder->state() != QMediaRecorder::StoppedState);
  }

  static QVariant boxValue(const QComboBox *box)
  {
      int idx = box->currentIndex();
      if (idx == -1)
          return QVariant();

      return box->itemData(idx);
  }

  void AudioRecorder::toggleRecord()
  {
      if (audioRecorder->state() == QMediaRecorder::StoppedState) {
          audioRecorder->setAudioInput(boxValue(ui->audioDeviceBox).toString());

          QAudioEncoderSettings settings;
          settings.setCodec(boxValue(ui->audioCodecBox).toString());
          settings.setSampleRate(boxValue(ui->sampleRateBox).toInt());
          settings.setBitRate(boxValue(ui->bitrateBox).toInt());
          settings.setChannelCount(boxValue(ui->channelsBox).toInt());
          settings.setQuality(QMultimedia::EncodingQuality(ui->qualitySlider->value()));
          settings.setEncodingMode(ui->constantQualityRadioButton->isChecked() ?
                                   QMultimedia::ConstantQualityEncoding :
                                   QMultimedia::ConstantBitRateEncoding);

          QString container = boxValue(ui->containerBox).toString();

          audioRecorder->setEncodingSettings(settings, QVideoEncoderSettings(), container);
          audioRecorder->record();
      }
      else {
          audioRecorder->stop();
      }
  }

  void AudioRecorder::togglePause()
  {
      if (audioRecorder->state() != QMediaRecorder::PausedState)
          audioRecorder->pause();
      else
          audioRecorder->record();
  }

  void AudioRecorder::setOutputLocation()
  {
      QString fileName = QFileDialog::getSaveFileName();
      audioRecorder->setOutputLocation(QUrl::fromLocalFile(fileName));
      outputLocationSet = true;
  }

  void AudioRecorder::displayErrorMessage()
  {
      ui->statusbar->showMessage(audioRecorder->errorString());
  }

  void AudioRecorder::clearAudioLevels()
  {
      for (int i = 0; i < audioLevels.size(); ++i)
          audioLevels.at(i)->setLevel(0);
  }

  // This function returns the maximum possible sample value for a given audio format
  qreal getPeakValue(const QAudioFormat& format)
  {
      // Note: Only the most common sample formats are supported
      if (!format.isValid())
          return qreal(0);

      if (format.codec() != "audio/pcm")
          return qreal(0);

      switch (format.sampleType()) {
      case QAudioFormat::Unknown:
          break;
      case QAudioFormat::Float:
          if (format.sampleSize() != 32) // other sample formats are not supported
              return qreal(0);
          return qreal(1.00003);
      case QAudioFormat::SignedInt:
          if (format.sampleSize() == 32)
              return qreal(INT_MAX);
          if (format.sampleSize() == 16)
              return qreal(SHRT_MAX);
          if (format.sampleSize() == 8)
              return qreal(CHAR_MAX);
          break;
      case QAudioFormat::UnSignedInt:
          if (format.sampleSize() == 32)
              return qreal(UINT_MAX);
          if (format.sampleSize() == 16)
              return qreal(USHRT_MAX);
          if (format.sampleSize() == 8)
              return qreal(UCHAR_MAX);
          break;
      }

      return qreal(0);
  }

  // returns the audio level for each channel
  QVector<qreal> getBufferLevels(const QAudioBuffer& buffer)
  {
      QVector<qreal> values;

      if (!buffer.format().isValid() || buffer.format().byteOrder() != QAudioFormat::LittleEndian)
          return values;

      if (buffer.format().codec() != "audio/pcm")
          return values;

      int channelCount = buffer.format().channelCount();
      values.fill(0, channelCount);
      qreal peak_value = getPeakValue(buffer.format());
      if (qFuzzyCompare(peak_value, qreal(0)))
          return values;

      switch (buffer.format().sampleType()) {
      case QAudioFormat::Unknown:
      case QAudioFormat::UnSignedInt:
          if (buffer.format().sampleSize() == 32)
              values = getBufferLevels(buffer.constData<quint32>(), buffer.frameCount(), channelCount);
          if (buffer.format().sampleSize() == 16)
              values = getBufferLevels(buffer.constData<quint16>(), buffer.frameCount(), channelCount);
          if (buffer.format().sampleSize() == 8)
              values = getBufferLevels(buffer.constData<quint8>(), buffer.frameCount(), channelCount);
          for (int i = 0; i < values.size(); ++i)
              values[i] = qAbs(values.at(i) - peak_value / 2) / (peak_value / 2);
          break;
      case QAudioFormat::Float:
          if (buffer.format().sampleSize() == 32) {
              values = getBufferLevels(buffer.constData<float>(), buffer.frameCount(), channelCount);
              for (int i = 0; i < values.size(); ++i)
                  values[i] /= peak_value;
          }
          break;
      case QAudioFormat::SignedInt:
          if (buffer.format().sampleSize() == 32)
              values = getBufferLevels(buffer.constData<qint32>(), buffer.frameCount(), channelCount);
          if (buffer.format().sampleSize() == 16)
              values = getBufferLevels(buffer.constData<qint16>(), buffer.frameCount(), channelCount);
          if (buffer.format().sampleSize() == 8)
              values = getBufferLevels(buffer.constData<qint8>(), buffer.frameCount(), channelCount);
          for (int i = 0; i < values.size(); ++i)
              values[i] /= peak_value;
          break;
      }

      return values;
  }

  template <class T>
  QVector<qreal> getBufferLevels(const T *buffer, int frames, int channels)
  {
      QVector<qreal> max_values;
      max_values.fill(0, channels);

      for (int i = 0; i < frames; ++i) {
          for (int j = 0; j < channels; ++j) {
              qreal value = qAbs(qreal(buffer[i * channels + j]));
              if (value > max_values.at(j))
                  max_values.replace(j, value);
          }
      }

      return max_values;
  }

  void AudioRecorder::processBuffer(const QAudioBuffer& buffer)
  {
      if (audioLevels.count() != buffer.format().channelCount()) {
          qDeleteAll(audioLevels);
          audioLevels.clear();
          for (int i = 0; i < buffer.format().channelCount(); ++i) {
              QAudioLevel *level = new QAudioLevel(ui->centralwidget);
              audioLevels.append(level);
              ui->levelsLayout->addWidget(level);
          }
      }

      QVector<qreal> levels = getBufferLevels(buffer);
      for (int i = 0; i < levels.count(); ++i)
          audioLevels.at(i)->setLevel(levels.at(i));
  }