bool AudioMixerSlave::prepareMix(const SharedNodePointer& listener) {
AvatarAudioStream* listenerAudioStream = static_cast<AudioMixerClientData*>(listener->getLinkedData())->getAvatarAudioStream();
AudioMixerClientData* listenerData = static_cast<AudioMixerClientData*>(listener->getLinkedData());
// if we received an invalid position from this listener, then refuse to make them a mix
// because we don't know how to do it properly
if (!listenerAudioStream->hasValidPosition()) {
return false;
}
// zero out the mix for this listener
memset(_mixSamples, 0, sizeof(_mixSamples));
bool isThrottling = _throttlingRatio > 0.0f;
std::vector<std::pair<float, SharedNodePointer>> throttledNodes;
typedef void (AudioMixerSlave::*MixFunctor)(
AudioMixerClientData&, const QUuid&, const AvatarAudioStream&, const PositionalAudioStream&);
auto forAllStreams = [&](const SharedNodePointer& node, AudioMixerClientData* nodeData, MixFunctor mixFunctor) {
auto nodeID = node->getUUID();
for (auto& streamPair : nodeData->getAudioStreams()) {
auto nodeStream = streamPair.second;
(this->*mixFunctor)(*listenerData, nodeID, *listenerAudioStream, *nodeStream);
}
};
#ifdef HIFI_AUDIO_MIXER_DEBUG
auto mixStart = p_high_resolution_clock::now();
#endif
std::for_each(_begin, _end, [&](const SharedNodePointer& node) {
AudioMixerClientData* nodeData = static_cast<AudioMixerClientData*>(node->getLinkedData());
if (!nodeData) {
return;
}
if (*node == *listener) {
// only mix the echo, if requested
for (auto& streamPair : nodeData->getAudioStreams()) {
auto nodeStream = streamPair.second;
if (nodeStream->shouldLoopbackForNode()) {
mixStream(*listenerData, node->getUUID(), *listenerAudioStream, *nodeStream);
}
}
} else if (!listenerData->shouldIgnore(listener, node, _frame)) {
if (!isThrottling) {
forAllStreams(node, nodeData, &AudioMixerSlave::mixStream);
} else {
auto nodeID = node->getUUID();
// compute the node's max relative volume
float nodeVolume = 0.0f;
for (auto& streamPair : nodeData->getAudioStreams()) {
auto nodeStream = streamPair.second;
// approximate the gain
glm::vec3 relativePosition = nodeStream->getPosition() - listenerAudioStream->getPosition();
float gain = approximateGain(*listenerAudioStream, *nodeStream, relativePosition);
// modify by hrtf gain adjustment
auto& hrtf = listenerData->hrtfForStream(nodeID, nodeStream->getStreamIdentifier());
gain *= hrtf.getGainAdjustment();
auto streamVolume = nodeStream->getLastPopOutputTrailingLoudness() * gain;
nodeVolume = std::max(streamVolume, nodeVolume);
}
// max-heapify the nodes by relative volume
throttledNodes.push_back({ nodeVolume, node });
std::push_heap(throttledNodes.begin(), throttledNodes.end());
}
}
});
if (isThrottling) {
// pop the loudest nodes off the heap and mix their streams
int numToRetain = (int)(std::distance(_begin, _end) * (1 - _throttlingRatio));
for (int i = 0; i < numToRetain; i++) {
if (throttledNodes.empty()) {
break;
}
std::pop_heap(throttledNodes.begin(), throttledNodes.end());
auto& node = throttledNodes.back().second;
AudioMixerClientData* nodeData = static_cast<AudioMixerClientData*>(node->getLinkedData());
forAllStreams(node, nodeData, &AudioMixerSlave::mixStream);
throttledNodes.pop_back();
}
// throttle the remaining nodes' streams
for (const std::pair<float, SharedNodePointer>& nodePair : throttledNodes) {
auto& node = nodePair.second;
AudioMixerClientData* nodeData = static_cast<AudioMixerClientData*>(node->getLinkedData());
forAllStreams(node, nodeData, &AudioMixerSlave::throttleStream);
}
}
#ifdef HIFI_AUDIO_MIXER_DEBUG
auto mixEnd = p_high_resolution_clock::now();
auto mixTime = std::chrono::duration_cast<std::chrono::nanoseconds>(mixEnd - mixStart);
stats.mixTime += mixTime.count();
#endif
// check for silent audio before limiting
// limiting uses a dither and can only guarantee abs(sample) <= 1
bool hasAudio = false;
for (int i = 0; i < AudioConstants::NETWORK_FRAME_SAMPLES_STEREO; ++i) {
if (_mixSamples[i] != 0.0f) {
hasAudio = true;
break;
}
}
// use the per listener AudioLimiter to render the mixed data
listenerData->audioLimiter.render(_mixSamples, _bufferSamples, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
return hasAudio;
}
