node-polyglot/google-cloud/Speech.js

const speech = require("@google-cloud/speech");
const Translate = require('./Translate');
const translate = new Translate('node-polyglot');

/**
 * Class Responsible for dealing with Google's Speech Recognition API
 */
class Speech {
  constructor() {
    /** @type {speech.SpeechClient} */
    this.client = new speech.SpeechClient();
    /** @type {Stream} */
    this.recognize = null;
    /** @type {boolean} */
    this.enabled = false;
  }

  /**
   * Getter for the Google API Stream we can write to.
   * @returns {Stream}  - this.recognize
   */
  getStream() {
    return this.recognize;
  }

  /**
   * Stops the GoogleAPI Stream.
   */
  stopRecognition() {
    if (this.recognize) this.recognize.end();
    this.recognize = null;
    this.enabled = false;
  }

  /**
   * Starts the Google API Stream
   * @param {string} lang - Language Code e.g en-CA for Canadian English
   * @param {string} target - Language Code e.g. "en" for English
   */
  startRecognition(lang, target) {
    this.enabled = true;

    const request = {
      config: {
        encoding: "LINEAR16",
        sampleRateHertz: 16000,
        languageCode: lang,
        profanityFilter: false,
        enableWordTimeOffsets: true
      },
      interimResults: true // If you want interim results, set this to true
    };

    this.recognize = this.client
      .streamingRecognize(request)
      .on("error", console.error)
      .on("data", data => {

        if (data.results[0].alternatives[0] !== undefined) {
          let text = data.results[0].alternatives[0].transcript;

          translate.speech(text, target).then(translation => {
            console.log(`${lang}: ${text} | ${target}: ${translation} (${data.results[0].alternatives[0].confidence})`);

          }).catch(err => console.error(err));

        }

        // if end of utterance, let's restart stream
        // this is a small hack. After 65 seconds of silence, the stream will still throw an error for speech length limit
        if (data.results[0] && data.results[0].isFinal) {
          this.stopRecognition();
          this.startRecognition(lang, target);
          // console.log('restarted stream serverside');
        }
      });
  }
}

module.exports = Speech;