Method read

source/base/StarMixer.cpp:231–410

}

void Mixer::read(int16_t* outBuffer, size_t frameCount, ExtraMixFunction extraMixFunction) {
  // Make this method as least locky as possible by copying all the needed
  // member data before the expensive audio / effect stuff.
  float speed;
  unsigned sampleRate;
  unsigned channels;
  float volume;
  float volumeVelocity;
  float targetVolume;
  Map<MixerGroup, RampedValue> groupVolumes;

  {
    MutexLocker locker(m_mutex);
    speed = m_speed;
    sampleRate = m_sampleRate;
    channels = m_channels;
    volume = m_volume.value;
    volumeVelocity = m_volume.velocity;
    targetVolume = m_volume.target;
    groupVolumes = m_groupVolumes;
  }

  size_t bufferSize = frameCount * m_channels;
  m_mixBuffer.resize(bufferSize, 0);

  float time = (float)frameCount / sampleRate;
  float beginVolume = volume;
  float endVolume = approach(targetVolume, volume, volumeVelocity * time);

  Map<MixerGroup, float> groupEndVolumes;
  for (auto p : groupVolumes)
    groupEndVolumes[p.first] = approach(p.second.target, p.second.value, p.second.velocity * time);

  auto sampleStartTime = Time::millisecondsSinceEpoch();
  unsigned millisecondsInBuffer = (bufferSize * 1000) / (channels * sampleRate);
  auto sampleEndTime = sampleStartTime + millisecondsInBuffer;

  for (size_t i = 0; i < bufferSize; ++i)
    outBuffer[i] = 0;

  {
    MutexLocker locker(m_queueMutex);
    // Mix all active sounds
    for (auto& p : m_audios) {
      auto& audioInstance = p.first;
      auto& audioState = p.second;

      MutexLocker audioLocker(audioInstance->m_mutex);

      if (audioInstance->m_finished)
        continue;

      if (audioInstance->m_clockStart && *audioInstance->m_clockStart > sampleEndTime)
        continue;

      float groupVolume = groupVolumes[audioInstance->m_mixerGroup].value;
      float groupEndVolume = groupEndVolumes[audioInstance->m_mixerGroup];