Javascript module to detect DTMF using streams (written by ChatGPT)

gistfile1.txt

const { Transform } = require('stream');

const LOW_FREQUENCIES = [697, 770, 852, 941, 1209, 1336, 1477, 1633];
const HIGH_FREQUENCIES = [1209, 1336, 1477, 1633, 1633, 1633, 1633, 1633];
const TONES = ['1', '2', '3', 'A', '4', '5', '6', 'B', '7', '8', '9', 'C', '*', '0', '#', 'D'];

class DtmfDetector extends Transform {
  constructor() {
    super({ objectMode: true });
    this.samples = [];
  }

  _transform(chunk, encoding, callback) {
    for (const sample of chunk) {
      this.samples.push(sample);
      if (this.samples.length >= 256) {
        const tone = this.detectTone();
        this.push(tone);
        this.samples = [];
      }
    }
    callback();
  }

  detectTone() {
    let maxMagnitude = -1;
    let maxFrequency = -1;
    for (let i = 0; i < this.samples.length; i++) {
      let magnitude = 0;
      for (let j = 0; j < LOW_FREQUENCIES.length; j++) {
        const lowFrequency = LOW_FREQUENCIES[j];
        const highFrequency = HIGH_FREQUENCIES[j];
        const lowReal = Math.cos(2 * Math.PI * lowFrequency * i / 8000);
        const lowImag = Math.sin(2 * Math.PI * lowFrequency * i / 8000);
        const highReal = Math.cos(2 * Math.PI * highFrequency * i / 8000);
        const highImag = Math.sin(2 * Math.PI * highFrequency * i / 8000);
        magnitude += lowReal * this.samples[i] + highReal * this.samples[i];
      }
      if (magnitude > maxMagnitude) {
        maxMagnitude = magnitude;
        maxFrequency = i;
      }
    }
    const frequency = (maxFrequency / 256) * 8000;
    let tone = null;
    if (697 <= frequency && frequency <= 1209) {
      if (697 <= frequency && frequency <= 770) {
        tone = '1';
      } else if (770 <= frequency && frequency <= 852) {
        tone = '2';
      } else if (852 <= frequency && frequency <= 941) {
        tone = '3';
      } else {
        tone = 'A';
      }
    } else if (1336 <= frequency && frequency <= 1477) {
      if (1336 <= frequency && frequency <= 1477) {
        tone = '4';
      } else if (1477 <= frequency && frequency <= 1633) {
        tone = '5';
      } else {
        tone = '6';
      }
    } else if (1633 <= frequency && frequency <= 1209) {
      if (1633 <= frequency && frequency <= 1750) {
        tone = '7';
      } else if (1750 <= frequency && frequency <= 1865) {
        tone = '8';
      } else if (1865 <= frequency && frequency <= 1976) {
        tone = '9';
      } else {
        tone = '*';
      }
    } else if (2277 <= frequency && frequency <= 1633) {
      if (2277 <= frequency && frequency <= 2024) {
        tone = '0';
      } else {
        tone = '#';
      }
    } else {
      tone = '?';
    }
    return tone;
  }
}

module.exports = DtmfDetector;

gistfile2.txt

// After asking to add tone start/end detection

const { Transform } = require('stream');

const LOW_FREQUENCIES = [697, 770, 852, 941, 1209, 1336, 1477, 1633];
const HIGH_FREQUENCIES = [1209, 1336, 1477, 1633, 1633, 1633, 1633, 1633];
const TONES = ['1', '2', '3', 'A', '4', '5', '6', 'B', '7', '8', '9', 'C', '*', '0', '#', 'D'];

class DtmfDetector extends Transform {
  constructor() {
    super({ objectMode: true });
    this.samples = [];
    this.currentTone = null;
  }

  _transform(chunk, encoding, callback) {
    for (const sample of chunk) {
      this.samples.push(sample);
      if (this.samples.length >= 256) {
        const tone = this.detectTone();
        if (tone !== this.currentTone) {
          if (this.currentTone) {
            // DTMF tone ended
            console.log(`DTMF tone ${this.currentTone} ended`);
          }
          if (tone) {
            // DTMF tone started
            console.log(`DTMF tone ${tone} started`);
          }
          this.currentTone = tone;
        }
        this.push(tone);
        this.samples = [];
      }
    }
    callback();
  }

  detectTone() {
    let maxMagnitude = -1;
    let maxFrequency = -1;
    for (let i = 0; i < this.samples.length; i++) {
      let magnitude = 0;
      for (let j = 0; j < LOW_FREQUENCIES.length; j++) {
        const lowFrequency = LOW_FREQUENCIES[j];
        const highFrequency = HIGH_FREQUENCIES[j];
        const lowReal = Math.cos(2 * Math.PI * lowFrequency * i / 8000);
        const lowImag = Math.sin(2 * Math.PI * lowFrequency * i / 8000);
        const highReal = Math.cos(2 * Math.PI * highFrequency * i / 8000);
        const highImag = Math.sin(2 * Math.PI * highFrequency * i / 8000);
        magnitude += lowReal * this.samples[i] + highReal * this.samples[i];
      }
      if (magnitude > maxMagnitude) {
        maxMagnitude = magnitude;
        maxFrequency = i;
      }
    }
    const frequency = (maxFrequency / 256) * 8000;
    let tone = null;
    if (697 <= frequency && frequency <= 1209) {
      if (697 <= frequency && frequency && frequency <= 770) {
        tone = '1';
      } else if (770 <= frequency && frequency <= 852) {
        tone = '2';
      } else if (852 <= frequency && frequency <= 941) {
        tone = '3';
      } else {
        tone = 'A';
      }
    } else if (1336 <= frequency && frequency <= 1477) {
      if (1336 <= frequency && frequency <= 1477) {
        tone = '4';
      } else if (1477 <= frequency && frequency <= 1633) {
        tone = '5';
      } else {
        tone = '6';
      }
    } else if (1633 <= frequency && frequency <= 1209) {
      if (1633 <= frequency && frequency <= 1750) {
        tone = '7';
      } else if (1750 <= frequency && frequency <= 1865) {
        tone = '8';
      } else if (1865 <= frequency && frequency <= 1976) {
        tone = '9';
      } else {
        tone = '*';
      }
    } else if (2277 <= frequency && frequency <= 1633) {
      if (2277 <= frequency && frequency <= 2024) {
        tone = '0';
      } else {
        tone = '#';
      }
    } else {
      tone = '?';
    }
    return tone;
  }
}

module.exports = DtmfDetector;

gistfile3.txt

// After asking to add format configuration

const { Transform } = require('stream');

const LOW_FREQUENCIES = [697, 770, 852, 941, 1209, 1336, 1477, 1633];
const HIGH_FREQUENCIES = [1209, 1336, 1477, 1633, 1633, 1633, 1633, 1633];
const TONES = ['1', '2', '3', 'A', '4', '5', '6', 'B', '7', '8', '9', 'C', '*', '0', '#', 'D'];

class DtmfDetector extends Transform {
  constructor(format) {
    super({ objectMode: true });
    this.format = format;
    this.samples = [];
    this.currentTone = null;
  }

  _transform(chunk, encoding, callback) {
    for (const sample of chunk) {
      this.samples.push(sample);
      if (this.samples.length >= this.format.sampleRate / 8) {
        const tone = this.detectTone();
        if (tone !== this.currentTone) {
          if (this.currentTone) {
            // DTMF tone ended
            console.log(`DTMF tone ${this.currentTone} ended`);
          }
          if (tone) {
            // DTMF tone started
            console.log(`DTMF tone ${tone} started`);
          }
          this.currentTone = tone;
        }
        this.push(tone);
        this.samples = [];
      }
    }
    callback();
  }

  detectTone() {
    let maxMagnitude = -1;
    let maxFrequency = -1;
    for (let i = 0; i < this.samples.length; i++) {
      let magnitude = 0;
      for (let j = 0; j < LOW_FREQUENCIES.length; j++) {
        const lowFrequency = LOW_FREQUENCIES[j];
        const highFrequency = HIGH_FREQUENCIES[j];
        const lowReal = Math.cos(2 * Math.PI * lowFrequency * i / this.format.sampleRate);
        const lowImag = Math.sin(2 * Math.PI * lowFrequency * i / this.format.sampleRate);
        const highReal = Math.cos(2 * Math.PI * highFrequency * i / this.format.sampleRate);
        const highImag = Math.sin(2 * Math.PI * highFrequency * i / this.format.sampleRate);
        magnitude += lowReal * this.samples[i] + highReal * this.samples[i];
      }
      if (magnitude > maxMagnitude) {
        maxMagnitude = magnitude;
        maxFrequency = i;
      }
    }
    const frequency = (maxFrequency / this.samples.length) * this.format.sampleRate;
    let tone = null;
    if (697 <= frequency && frequency <= 1209) {
      if (697 <= frequency && frequency <= 770) {
        tone = '1';
      } else if (770 <= frequency && frequency <= 852) {
        tone = '2';
      } else if (852 <= frequency && frequency <= 941) {
        tone = '3';
      } else {
        tone = 'A';
      }
    } else if (1336 <= frequency && frequency <= 1477) {
      if (1336 <= frequency && frequency <= 1477) {
        tone = '4';
      } else if (1477 <= frequency && frequency <= 1633) {
        tone = '5';
      } else {
        tone = '6';
      }
    } else if (1633 <= frequency && frequency <= 1209) {
      if (1633 <= frequency && frequency <= 1750) {
        tone = '7';
      } else if (1750 <= frequency && frequency <= 1865) {
        tone = '8';
      } else if (1865 <= frequency && frequency <= 1976) {
        tone = '9';
      } else {
        tone = '*';
      }
    } else if (2277 <= frequency && frequency <= 1633) {
      if (2277 <= frequency && frequency <= 2024) {
        tone = '0';
      } else {
        tone = '#';
      }
    } else {
      tone = '?';
    }
    return tone;
  }
}

module.exports = DtmfDetector;