client-sdk-flutter/shared_cpp/audio_visualizer.cpp at main · livekit/client-sdk-flutter · GitHub

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#include "audio_visualizer.h"

#include <algorithm>

#include <chrono>

double CurrentTime() {

return static_cast<double>(

std::chrono::duration_cast<std::chrono::milliseconds>(

std::chrono::system_clock::now().time_since_epoch())

.count()) /

1000.0;

}

int magnitudeIndex(std::vector<float> magnitudes, float frequency,

float sampleRate) {

return static_cast<int>(float(magnitudes.size()) * frequency / sampleRate /

2);

}

std::vector<float> computeBands(std::vector<float> magnitudes,

float minFrequency, float maxFrequency,

int bandsCount, float sampleRate) {

float actualMaxFrequency = std::min(sampleRate / 2, maxFrequency);

std::vector<float> bandMagnitudes(bandsCount, 0.0f);

int magLowerRange = magnitudeIndex(magnitudes, minFrequency, sampleRate);

int magUpperRange =

magnitudeIndex(magnitudes, actualMaxFrequency, sampleRate);

float ratio = float(magUpperRange - magLowerRange) / float(bandsCount);

for (int i = 0; i < bandsCount; ++i) {

int magsStartIdx =

static_cast<int>(floorf(float(i) * ratio)) + magLowerRange;

int magsEndIdx =

static_cast<int>(floorf(float(i + 1) * ratio)) + magLowerRange;

int count = magsEndIdx - magsStartIdx;

if (count > 0) {

float sum = 0;

for (int j = magsStartIdx; j < magsEndIdx; ++j) {

sum += magnitudes[j];

}

bandMagnitudes[i] = sum / float(count);

} else {

bandMagnitudes[i] = magnitudes[magsStartIdx];

}

return bandMagnitudes;

}

/// Centers the sorted bands by placing higher values in the middle.

std::vector<float> centerBands(const std::vector<float> &sortedBands) {

std::vector<float> centeredBands(sortedBands.size(), 0);

size_t leftIndex = sortedBands.size() / 2;

size_t rightIndex = leftIndex;

for (size_t index = 0; index < sortedBands.size(); ++index) {

if (index % 2 == 0) {

// Place value to the right

centeredBands[rightIndex] = sortedBands[index];

rightIndex += 1;

} else {

// Place value to the left

leftIndex -= 1;

centeredBands[leftIndex] = sortedBands[index];

}

return centeredBands;

}

AudioVisualizer::AudioVisualizer(int bands_count, bool is_centered,

double smoothing_time_constant,

float min_frequency, float max_frequency,

float min_db, float max_db)

: bands_count_(bands_count), is_centered_(is_centered),

min_frequency_(min_frequency), max_frequency_(max_frequency),

min_db_(min_db), max_db_(max_db),

smoothing_time_constant_(smoothing_time_constant),

bands_(bands_count, 0.0f),

fft_processor_(std::make_unique<FFTProcessor>(

FFTProcessor::kDefaultFFTSize, smoothing_time_constant_)) {}

AudioVisualizer::~AudioVisualizer() {}

bool AudioVisualizer::Process(const int16_t *audioData, unsigned int numSamples,

float sampleRate, std::vector<float> &output) {

fft_processor_->WriteInput(audioData, numSamples);

std::vector<float> magnitudes(FFTProcessor::kDefaultFFTSize / 2, 0.0f);

fft_processor_->GetFloatFrequencyData(magnitudes, CurrentTime());

auto bands = computeBands(magnitudes, min_frequency_, max_frequency_,

bands_count_, sampleRate);

for (int i = 0; i < bands.size(); ++i) {

float db = 1.0f - (fmax(min_db_, fmin(max_db_, bands[i])) * -1.0f) / 100.0f;

db = std::sqrt(db);

bands_[i] = db;

}

if (is_centered_) {

std::sort(bands_.begin(), bands_.end(), std::greater<float>());

bands_ = centerBands(bands_);

}

output = bands_;

return true;

}

client-sdk-flutter/shared_cpp/audio_visualizer.cpp at main · livekit/client-sdk-flutter · GitHub

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