void AudioMixer::addStreamToMixForListeningNodeWithStream(AudioMixerClientData& listenerNodeData, const PositionalAudioStream& streamToAdd, const QUuid& sourceNodeID, const AvatarAudioStream& listeningNodeStream) { // to reduce artifacts we calculate the gain and azimuth for every source for this listener // even if we are not going to end up mixing in this source ++_totalMixes; // this ensures that the tail of any previously mixed audio or the first block of new audio sounds correct // check if this is a server echo of a source back to itself bool isEcho = (&streamToAdd == &listeningNodeStream); glm::vec3 relativePosition = streamToAdd.getPosition() - listeningNodeStream.getPosition(); // figure out the distance between source and listener float distance = glm::max(glm::length(relativePosition), EPSILON); // figure out the gain for this source at the listener float gain = gainForSource(streamToAdd, listeningNodeStream, relativePosition, isEcho); // figure out the azimuth to this source at the listener float azimuth = isEcho ? 0.0f : azimuthForSource(streamToAdd, listeningNodeStream, relativePosition); float repeatedFrameFadeFactor = 1.0f; static const int HRTF_DATASET_INDEX = 1; if (!streamToAdd.lastPopSucceeded()) { bool forceSilentBlock = true; if (_streamSettings._repetitionWithFade && !streamToAdd.getLastPopOutput().isNull()) { // reptition with fade is enabled, and we do have a valid previous frame to repeat // so we mix the previously-mixed block // this is preferable to not mixing it at all to avoid the harsh jump to silence // we'll repeat the last block until it has a block to mix // and we'll gradually fade that repeated block into silence. // calculate its fade factor, which depends on how many times it's already been repeated. repeatedFrameFadeFactor = calculateRepeatedFrameFadeFactor(streamToAdd.getConsecutiveNotMixedCount() - 1); if (repeatedFrameFadeFactor > 0.0f) { // apply the repeatedFrameFadeFactor to the gain gain *= repeatedFrameFadeFactor; forceSilentBlock = false; } } if (forceSilentBlock) { // we're deciding not to repeat either since we've already done it enough times or repetition with fade is disabled // in this case we will call renderSilent with a forced silent block // this ensures the correct tail from the previously mixed block and the correct spatialization of first block // of any upcoming audio if (!streamToAdd.isStereo() && !isEcho) { // get the existing listener-source HRTF object, or create a new one auto& hrtf = listenerNodeData.hrtfForStream(sourceNodeID, streamToAdd.getStreamIdentifier()); // this is not done for stereo streams since they do not go through the HRTF static int16_t silentMonoBlock[AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL] = {}; hrtf.renderSilent(silentMonoBlock, _mixedSamples, HRTF_DATASET_INDEX, azimuth, distance, gain, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL); ++_hrtfSilentRenders;; } return; } } // grab the stream from the ring buffer AudioRingBuffer::ConstIterator streamPopOutput = streamToAdd.getLastPopOutput(); if (streamToAdd.isStereo() || isEcho) { // this is a stereo source or server echo so we do not pass it through the HRTF // simply apply our calculated gain to each sample if (streamToAdd.isStereo()) { for (int i = 0; i < AudioConstants::NETWORK_FRAME_SAMPLES_STEREO; ++i) { _mixedSamples[i] += float(streamPopOutput[i] * gain / AudioConstants::MAX_SAMPLE_VALUE); } ++_manualStereoMixes; } else { for (int i = 0; i < AudioConstants::NETWORK_FRAME_SAMPLES_STEREO; i += 2) { auto monoSample = float(streamPopOutput[i / 2] * gain / AudioConstants::MAX_SAMPLE_VALUE); _mixedSamples[i] += monoSample; _mixedSamples[i + 1] += monoSample; } ++_manualEchoMixes; } return; } // get the existing listener-source HRTF object, or create a new one auto& hrtf = listenerNodeData.hrtfForStream(sourceNodeID, streamToAdd.getStreamIdentifier()); static int16_t streamBlock[AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL]; streamPopOutput.readSamples(streamBlock, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL); // if the frame we're about to mix is silent, simply call render silent and move on if (streamToAdd.getLastPopOutputLoudness() == 0.0f) { // silent frame from source // we still need to call renderSilent via the HRTF for mono source hrtf.renderSilent(streamBlock, _mixedSamples, HRTF_DATASET_INDEX, azimuth, distance, gain, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL); ++_hrtfSilentRenders; return; } if (_performanceThrottlingRatio > 0.0f && streamToAdd.getLastPopOutputTrailingLoudness() / glm::length(relativePosition) <= _minAudibilityThreshold) { // the mixer is struggling so we're going to drop off some streams // we call renderSilent via the HRTF with the actual frame data and a gain of 0.0 hrtf.renderSilent(streamBlock, _mixedSamples, HRTF_DATASET_INDEX, azimuth, distance, 0.0f, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL); ++_hrtfStruggleRenders; return; } ++_hrtfRenders; // mono stream, call the HRTF with our block and calculated azimuth and gain hrtf.render(streamBlock, _mixedSamples, HRTF_DATASET_INDEX, azimuth, distance, gain, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL); }