在nodejs中构建自己的IT声音混合器

<code class="javascript">class EightBitMixer {
  constructor(sampleRate = 22050, channels = 2) {
    this.sampleRate = sampleRate;
    this.channels = channels;
    this.audioChannels = [];
    this.maxValue = 127; // 8位音频的最大幅度为127
    this.minValue = -128;
  }

  addChannel() {
    if (this.audioChannels.length >= this.channels) {
      throw new Error('已达到最大通道数');
    }
    const channel = {
      waveform: null,
      frequency: 440, // 默认值为A4音符
      volume: 1.0,
      enabled: true
    };
    this.audioChannels.push(channel);
    return this.audioChannels.length - 1; // 返回通道索引
  }

  generateSample(time) {
    let sample = 0;
    for (const channel of this.audioChannels) {
      if (channel.enabled && channel.waveform) {
        sample += channel.waveform(time, channel.frequency) * channel.volume;
      }
    }
    sample = Math.max(this.minValue, Math.min(this.maxValue, Math.round(sample)));
    return sample;
  }
}</code>

<code class="javascript">const waveforms = {
  square: (time, frequency) => {
    const period = 1 / frequency;
    return (time % period) < (period / 2) ? 127 : -128;
  },
  triangle: (time, frequency) => {
    const period = 1 / frequency;
    const phase = (time % period) / period;
    return -128 + (phase < 0.5 ? phase * 255 : (1 - phase) * 255);
  },
  sawtooth: (time, frequency) => {
    const period = 1 / frequency;
    const phase = (time % period) / period;
    return -128 + (phase * 255);
  },
  noise: () => Math.floor(Math.random() * 255) - 128
};</code>

<code class="javascript">const Speaker = require('speaker');

class EightBitMixer {
  // ...之前的代码...

  startPlayback() {
    const speaker = new Speaker({
      channels: 1, // 单声道输出
      bitDepth: 8, // 8位音频
      sampleRate: this.sampleRate
    });

    let time = 0;
    const generateAudio = () => {
      const bufferSize = 4096;
      const buffer = Buffer.alloc(bufferSize);
      for (let i = 0; i < bufferSize; i++) {
        buffer[i] = this.generateSample(time);
        time += 1 / this.sampleRate;
      }
      speaker.write(buffer);
      setTimeout(generateAudio, bufferSize / this.sampleRate * 1000);
    };
    generateAudio();
  }
}</code>

<code class="javascript">const mixer = new EightBitMixer();
const channel1 = mixer.addChannel();
mixer.audioChannels[channel1].waveform = waveforms.square;
mixer.audioChannels[channel1].frequency = 220; // A3音符
mixer.startPlayback();</code>

<code class="javascript">class EnvelopeGenerator {
  // ... (实现代码省略，与原文类似)...
}</code>

<code class="javascript">class Effect {
  process(sample) { return sample; }
}

class Distortion extends Effect {
  // ... (实现代码省略，与原文类似)...
}</code>