M5Tab5-UserDemo/app/apps/utils/audio/audio.cpp

/*
 * SPDX-FileCopyrightText: 2025 M5Stack Technology CO LTD
 *
 * SPDX-License-Identifier: MIT
 */
#include <vector>
#include <cmath>
#include <cstdlib>
#include <cstdint>
#include <algorithm>
#include <hal/hal.h>

static constexpr int SAMPLE_RATE = 48000;
static constexpr double PI       = 3.14159265358979323846;

// 简单线性包络：attack + decay
void generate_tone_with_linear_envelope(std::vector<int16_t>& buffer, double freq, double duration, double volume)
{
    int samples        = static_cast<int>(SAMPLE_RATE * duration);
    int attack_samples = SAMPLE_RATE * 0.005;  // 5ms attack
    for (int i = 0; i < samples; ++i) {
        double t         = static_cast<double>(i) / SAMPLE_RATE;
        double amplitude = 1.0;

        if (i < attack_samples) {
            amplitude = static_cast<double>(i) / attack_samples;  // Linear attack
        } else {
            amplitude = 1.0 - static_cast<double>(i - attack_samples) / (samples - attack_samples);  // Linear decay
        }

        double sample = std::sin(2.0 * PI * freq * t) * amplitude;
        int16_t s     = static_cast<int16_t>(sample * volume * 32767);
        buffer.push_back(s);  // Left
        buffer.push_back(s);  // Right
    }
}

namespace audio {

void play_tone(int frequency, double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    const int sample_rate = 48000;
    const int samples     = static_cast<int>(sample_rate * durationSec);
    std::vector<int16_t> buffer(samples * 2);  // 双声道

    const int fade_len    = 200;  // 淡出长度（采样点）
    const float amplitude = 32767.0f / 5;

    for (int i = 0; i < samples; ++i) {
        float amp = amplitude;

        // 应用结尾淡出（fade-out）
        if (i >= samples - fade_len) {
            float fade_factor = static_cast<float>(samples - i) / fade_len;
            amp *= fade_factor;
        }

        int16_t value     = static_cast<int16_t>(amp * sin(2.0 * M_PI * frequency * i / sample_rate));
        buffer[i * 2]     = value;  // 左声道
        buffer[i * 2 + 1] = value;  // 右声道
    }

    GetHAL()->audioPlay(buffer);
}

void play_melody(const std::vector<int>& midiList, double durationSec = 0.1)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    const int sample_rate      = 48000;
    const int samples_per_note = static_cast<int>(sample_rate * durationSec);
    const int fade_len         = 200;  // 每个音符结尾的淡出长度
    const float amplitude      = 32767.0f / 5;

    std::vector<int16_t> buffer;                             // 大 buffer 存放整首旋律
    buffer.reserve(midiList.size() * samples_per_note * 2);  // 双声道预留空间

    for (int midiNote : midiList) {
        for (int i = 0; i < samples_per_note; ++i) {
            float amp = amplitude;

            // 应用淡出（仅每个音符的结尾）
            if (i >= samples_per_note - fade_len) {
                float fade_factor = static_cast<float>(samples_per_note - i) / fade_len;
                amp *= fade_factor;
            }

            int16_t sample = 0;
            if (midiNote >= 0) {
                double freq = 440.0 * pow(2.0, (midiNote - 69) / 12.0);
                sample      = static_cast<int16_t>(amp * sin(2.0 * M_PI * freq * i / sample_rate));
            }

            buffer.push_back(sample);  // 左声道
            buffer.push_back(sample);  // 右声道
        }
    }

    GetHAL()->audioPlay(buffer);
}

void play_tone_from_midi(int midi, double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    double freq = 440.0 * std::pow(2.0, (midi - 69) / 12.0);
    play_tone(static_cast<int>(freq), durationSec);
}

void play_random_tone(int semitoneShift = 0, double durationSec = 0.15)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    std::vector<int> scale = {60, 62, 64, 65, 67, 69, 71};  // C大调音阶（C D E F G A B）

    int index = rand() % scale.size();
    int midi  = scale[index] + semitoneShift;

    play_tone_from_midi(midi, durationSec);
}

void play_next_tone_progression(double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    constexpr int REPEAT_EACH_CHORD = 1;
    constexpr int SEMITONE_SHIFT    = 24;

    static std::vector<int> melody = {60, 67, 69, 64, 65, 60, 65, 67};  // 15634145

    static size_t index       = 0;
    static int repeat_counter = -1;

    if (++repeat_counter >= REPEAT_EACH_CHORD) {
        repeat_counter = 0;
        index++;
    }

    int midi = melody[index % melody.size()] + SEMITONE_SHIFT;

    play_tone_from_midi(midi, durationSec);
}

void play_chord(const std::vector<int>& midiNotes, double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    std::vector<double> freqs;
    for (int midi : midiNotes) {
        double freq = 440.0 * std::pow(2.0, (midi - 69) / 12.0);
        freqs.push_back(freq);
    }

    std::vector<int16_t> buffer;
    std::vector<std::vector<int16_t>> tones;
    for (double freq : freqs) {
        std::vector<int16_t> tone;
        generate_tone_with_linear_envelope(tone, freq, durationSec, 0.35);
        tones.push_back(tone);
    }

    size_t num_samples = tones[0].size();
    buffer.resize(num_samples, 0);
    for (size_t i = 0; i < num_samples; ++i) {
        int32_t mixed = 0;
        for (auto& tone : tones) {
            mixed += tone[i];
        }
        buffer[i] = std::clamp((int)mixed, -32768, 32767);
    }

    GetHAL()->audioPlay(buffer);
}

void play_random_chord(int semitoneShift, double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    // C大调音阶
    std::vector<int> scale = {60, 62, 64, 65, 67, 69, 71};  // C D E F G A B

    // 随机 root 和和弦结构
    int root_index              = rand() % 4;  // 留出空间给三度五度
    int root                    = scale[root_index] + semitoneShift;
    int third                   = scale[root_index + 2] + semitoneShift;
    int fifth                   = scale[root_index + 4] + semitoneShift;
    std::vector<int> chord_midi = {root, third, fifth};

    play_chord(chord_midi, durationSec);
}

void play_next_chord_progression(double durationSec)
{
    if (GetHAL()->getSpeakerVolume() <= 0) {
        return;
    }

    constexpr int REPEAT_EACH_CHORD = 2;
    constexpr int SEMITONE_SHIFT    = 0;

    static std::vector<int> chord_roots = {60, 67, 69, 64, 65, 60, 65, 67};  // 15634145
    // static std::vector<int> chord_roots = { 60, 71, 69, 67, 65, 64, 62, 60 }; // 17654321
    // static std::vector<int> chord_roots = { 65, 67, 64, 69, 62, 67, 60 }; // 4536251
    // static std::vector<int> chord_roots = {65, 65, 64, 69, 62, 67, 60}; // 4436251

    static size_t current_chord_index = 0;
    static int repeat_counter         = -1;

    if (++repeat_counter >= REPEAT_EACH_CHORD) {
        repeat_counter = 0;
        current_chord_index++;
    }

    int root = chord_roots[current_chord_index % chord_roots.size()] + SEMITONE_SHIFT;

    // 判断是否为小和弦（只处理 Am）
    bool is_minor = (root % 12 == 9);  // MIDI 69, 81, 等都是 A

    std::vector<int> chord_midi = {root, root + (is_minor ? 3 : 4), root + 7};

    play_chord(chord_midi, durationSec);
}

}  // namespace audio