Qt 5.11 | Qt Multimedia | Media Player Example | histogramwidget.cpp Example File

Qt 5.11.3 Reference Documentation

# histogramwidget.cpp Example File

multimediawidgets/player/histogramwidget.cpp

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      #include "histogramwidget.h"
      #include <QPainter>
      #include <QHBoxLayout>

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

      class QAudioLevel : public QWidget
      {
          Q_OBJECT
      public:
          explicit QAudioLevel(QWidget *parent = nullptr);

          // Using [0; 1.0] range
          void setLevel(qreal level);

      protected:
          void paintEvent(QPaintEvent *event);

      private:
          qreal m_level = 0;
      };

      QAudioLevel::QAudioLevel(QWidget *parent)
          : QWidget(parent)
      {
          setMinimumHeight(15);
          setMaximumHeight(50);
      }

      void QAudioLevel::setLevel(qreal level)
      {
          if (m_level != level) {
              m_level = level;
              update();
          }
      }

      void QAudioLevel::paintEvent(QPaintEvent *event)
      {
          Q_UNUSED(event);

          QPainter painter(this);
          // draw level
          qreal widthLevel = m_level * width();
          painter.fillRect(0, 0, widthLevel, height(), Qt::red);
          // clear the rest of the control
          painter.fillRect(widthLevel, 0, width(), height(), Qt::black);
      }

      HistogramWidget::HistogramWidget(QWidget *parent)
          : QWidget(parent)
      {
          m_processor.moveToThread(&m_processorThread);
          qRegisterMetaType<QVector<qreal>>("QVector<qreal>");
          connect(&m_processor, &FrameProcessor::histogramReady, this, &HistogramWidget::setHistogram);
          m_processorThread.start(QThread::LowestPriority);
          setLayout(new QHBoxLayout);
      }

      HistogramWidget::~HistogramWidget()
      {
          m_processorThread.quit();
          m_processorThread.wait(10000);
      }

      void HistogramWidget::processFrame(const QVideoFrame &frame)
      {
          if (m_isBusy && frame.isValid())
              return; //drop frame

          m_isBusy = true;
          QMetaObject::invokeMethod(&m_processor, "processFrame",
                                    Qt::QueuedConnection, Q_ARG(QVideoFrame, frame), Q_ARG(int, m_levels));
      }

      // 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.isValid())
              return 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 HistogramWidget::processBuffer(const QAudioBuffer &buffer)
      {
          if (m_audioLevels.count() != buffer.format().channelCount()) {
              qDeleteAll(m_audioLevels);
              m_audioLevels.clear();
              for (int i = 0; i < buffer.format().channelCount(); ++i) {
                  QAudioLevel *level = new QAudioLevel(this);
                  m_audioLevels.append(level);
                  layout()->addWidget(level);
              }
          }

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

      void HistogramWidget::setHistogram(const QVector<qreal> &histogram)
      {
          m_isBusy = false;
          m_histogram = histogram;
          update();
      }

      void HistogramWidget::paintEvent(QPaintEvent *event)
      {
          Q_UNUSED(event);

          if (!m_audioLevels.isEmpty())
              return;

          QPainter painter(this);

          if (m_histogram.isEmpty()) {
              painter.fillRect(0, 0, width(), height(), QColor::fromRgb(0, 0, 0));
              return;
          }

          qreal barWidth = width() / (qreal)m_histogram.size();

          for (int i = 0; i < m_histogram.size(); ++i) {
              qreal h = m_histogram[i] * height();
              // draw level
              painter.fillRect(barWidth * i, height() - h, barWidth * (i + 1), height(), Qt::red);
              // clear the rest of the control
              painter.fillRect(barWidth * i, 0, barWidth * (i + 1), height() - h, Qt::black);
          }
      }

      void FrameProcessor::processFrame(QVideoFrame frame, int levels)
      {
          QVector<qreal> histogram(levels);

          do {
              if (!levels)
                  break;

              if (!frame.map(QAbstractVideoBuffer::ReadOnly))
                  break;

              if (frame.pixelFormat() == QVideoFrame::Format_YUV420P ||
                  frame.pixelFormat() == QVideoFrame::Format_NV12) {
                  // Process YUV data
                  uchar *b = frame.bits();
                  for (int y = 0; y < frame.height(); ++y) {
                      uchar *lastPixel = b + frame.width();
                      for (uchar *curPixel = b; curPixel < lastPixel; curPixel++)
                          histogram[(*curPixel * levels) >> 8] += 1.0;
                      b += frame.bytesPerLine();
                  }
              } else {
                  QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(frame.pixelFormat());
                  if (imageFormat != QImage::Format_Invalid) {
                      // Process RGB data
                      QImage image(frame.bits(), frame.width(), frame.height(), imageFormat);
                      image = image.convertToFormat(QImage::Format_RGB32);

                      const QRgb* b = (const QRgb*)image.bits();
                      for (int y = 0; y < image.height(); ++y) {
                          const QRgb *lastPixel = b + frame.width();
                          for (const QRgb *curPixel = b; curPixel < lastPixel; curPixel++)
                              histogram[(qGray(*curPixel) * levels) >> 8] += 1.0;
                          b = (const QRgb*)((uchar*)b + image.bytesPerLine());
                      }
                  }
              }

              // find maximum value
              qreal maxValue = 0.0;
              for (int i = 0; i < histogram.size(); i++) {
                  if (histogram[i] > maxValue)
                      maxValue = histogram[i];
              }

              if (maxValue > 0.0) {
                  for (int i = 0; i < histogram.size(); i++)
                      histogram[i] /= maxValue;
              }

              frame.unmap();
          } while (false);

          emit histogramReady(histogram);
      }

      #include "histogramwidget.moc"