C++ PositionalAudioStream::getLastPopOutputTrailingLoudness方法代码示例

//.........这里部分代码省略.........
            // 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);
}