Qt 5.9 | Qt Multimedia | Audio Recorder Example | audiorecorder.cpp Example File

Qt 5.9.4 Reference Documentation

# audiorecorder.cpp Example File

multimedia/audiorecorder/audiorecorder.cpp

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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));
      }