Method buildFrameIndex

app/src/MDF4/Player.cpp:848–904

* @brief Builds a sparse frame index for efficient streaming playback. */

 * @brief Builds a sparse frame index for efficient streaming playback.
 */
void MDF4::Player::buildFrameIndex()
{
  m_frameIndex.clear();
  m_channels.clear();
  m_sampleCache.clear();
  m_stringCache.clear();
  m_timestampCache.clear();
  m_activeChannels.clear();
  m_channelIsString.clear();
  m_masterTimeChannel = nullptr;

  if (!m_reader || !m_reader->IsOk())
    return;

  auto* file = m_reader->GetFile();
  if (!file)
    return;

  mdf::DataGroupList dataGroups;
  file->DataGroups(dataGroups);

  if (dataGroups.empty())
    return;

  std::vector<mdf::IChannel*> allChannels;
  std::map<mdf::IChannelGroup*, mdf::IChannel*> groupTimeChannels;
  int masterChannelCount = 0;
  collectAllChannels(dataGroups, allChannels, groupTimeChannels, masterChannelCount);

  const bool perGroupTime  = (masterChannelCount > 1);
  uint64_t legacyTimeRecId = 0;
  if (masterChannelCount == 1) {
    auto it             = groupTimeChannels.begin();
    m_masterTimeChannel = it->second;
    legacyTimeRecId     = it->first->RecordId();
    groupTimeChannels.clear();
  }

  m_channels = allChannels;

  m_channelIsString.clear();
  m_channelIsString.reserve(m_channels.size());
  for (const auto* ch : m_channels)
    m_channelIsString.push_back(isStringChannel(ch));

  for (auto* dg : dataGroups) {
    if (!dg)
      continue;

    readDataGroupWithObservers(dg, perGroupTime, groupTimeChannels);
  }

  if (m_isSerialStudioFile && !perGroupTime && m_masterTimeChannel)
    readLegacyTimestamps(dataGroups, legacyTimeRecId);

  buildFrameIndexFromCache();
}