How to use Web Speech API at chromium?

Question

How to use SpeechSynthesisUtterance() and window.speechSynthesis.speak() at chromium browser?

var msg = new SpeechSynthesisUtterance( "Hello I am browser" );
window.speechSynthesis.speak( msg );

yields no output at system speakers.

Issues with the API have bee noted The HTML5 SpeechSynthesis API is rubbish;

var voices = window.speechSynthesis.getVoices();

logs an empty array for voices identifier; and only chrome not chromium purportedly support Web Speech API Specification, the Web Speech API Demonstration sets value of html element at demonstration to utterance voiced when microphone is enabled at page.

At least some of the JavaScript relating to the functionality is apparently

var langs =
[['Afrikaans',       ['af-ZA']],
 ['Bahasa Indonesia',['id-ID']],
 ['Bahasa Melayu',   ['ms-MY']],
 ['Català',          ['ca-ES']],
 ['Čeština',         ['cs-CZ']],
 ['Dansk',           ['da-DK']],
 ['Deutsch',         ['de-DE']],
 ['English',         ['en-AU', 'Australia'],
                     ['en-CA', 'Canada'],
                     ['en-IN', 'India'],
                     ['en-NZ', 'New Zealand'],
                     ['en-ZA', 'South Africa'],
                     ['en-GB', 'United Kingdom'],
                     ['en-US', 'United States']],
 ['Español',         ['es-AR', 'Argentina'],
                     ['es-BO', 'Bolivia'],
                     ['es-CL', 'Chile'],
                     ['es-CO', 'Colombia'],
                     ['es-CR', 'Costa Rica'],
                     ['es-EC', 'Ecuador'],
                     ['es-SV', 'El Salvador'],
                     ['es-ES', 'España'],
                     ['es-US', 'Estados Unidos'],
                     ['es-GT', 'Guatemala'],
                     ['es-HN', 'Honduras'],
                     ['es-MX', 'México'],
                     ['es-NI', 'Nicaragua'],
                     ['es-PA', 'Panamá'],
                     ['es-PY', 'Paraguay'],
                     ['es-PE', 'Perú'],
                     ['es-PR', 'Puerto Rico'],
                     ['es-DO', 'República Dominicana'],
                     ['es-UY', 'Uruguay'],
                     ['es-VE', 'Venezuela']],
 ['Euskara',         ['eu-ES']],
 ['Filipino',        ['fil-PH']],
 ['Français',        ['fr-FR']],
 ['Galego',          ['gl-ES']],
 ['Hrvatski',        ['hr_HR']],
 ['IsiZulu',         ['zu-ZA']],
 ['Íslenska',        ['is-IS']],
 ['Italiano',        ['it-IT', 'Italia'],
                     ['it-CH', 'Svizzera']],
 ['Lietuvių',        ['lt-LT']],
 ['Magyar',          ['hu-HU']],
 ['Nederlands',      ['nl-NL']],
 ['Norsk bokmål',    ['nb-NO']],
 ['Polski',          ['pl-PL']],
 ['Português',       ['pt-BR', 'Brasil'],
                     ['pt-PT', 'Portugal']],
 ['Română',          ['ro-RO']],
 ['Slovenščina',     ['sl-SI']],
 ['Slovenčina',      ['sk-SK']],
 ['Suomi',           ['fi-FI']],
 ['Svenska',         ['sv-SE']],
 ['Tiếng Việt',      ['vi-VN']],
 ['Türkçe',          ['tr-TR']],
 ['Ελληνικά',        ['el-GR']],
 ['български',       ['bg-BG']],
 ['Pусский',         ['ru-RU']],
 ['Српски',          ['sr-RS']],
 ['Українська',      ['uk-UA']],
 ['한국어',            ['ko-KR']],
 ['中文',             ['cmn-Hans-CN', '普通话 (中国大陆)'],
                     ['cmn-Hans-HK', '普通话 (香港)'],
                     ['cmn-Hant-TW', '中文 (台灣)'],
                     ['yue-Hant-HK', '粵語 (香港)']],
 ['日本語',           ['ja-JP']],
 ['हिन्दी',            ['hi-IN']],
 ['ภาษาไทย',         ['th-TH']]];

for (var i = 0; i < langs.length; i++) {
  select_language.options[i] = new Option(langs[i][0], i);
}
select_language.selectedIndex = 7;
updateCountry();
select_dialect.selectedIndex = 6;
showInfo('info_start');

function updateCountry() {
  for (var i = select_dialect.options.length - 1; i >= 0; i--) {
    select_dialect.remove(i);
  }
  var list = langs[select_language.selectedIndex];
  for (var i = 1; i < list.length; i++) {
    select_dialect.options.add(new Option(list[i][1], list[i][0]));
  }
  select_dialect.style.visibility = list[1].length == 1 ? 'hidden' : 'visible';
}

var create_email = false;
var final_transcript = '';
var recognizing = false;
var ignore_onend;
var start_timestamp;
if (!('webkitSpeechRecognition' in window)) {
  upgrade();
} else {
  start_button.style.display = 'inline-block';
  var recognition = new webkitSpeechRecognition();
  recognition.continuous = true;
  recognition.interimResults = true;

  recognition.onstart = function() {
    recognizing = true;
    showInfo('info_speak_now');
    start_img.src = '/intl/en/chrome/assets/common/images/content/mic-animate.gif';
  };

  recognition.onerror = function(event) {
    if (event.error == 'no-speech') {
      start_img.src = '/intl/en/chrome/assets/common/images/content/mic.gif';
      showInfo('info_no_speech');
      ignore_onend = true;
    }
    if (event.error == 'audio-capture') {
      start_img.src = '/intl/en/chrome/assets/common/images/content/mic.gif';
      showInfo('info_no_microphone');
      ignore_onend = true;
    }
    if (event.error == 'not-allowed') {
      if (event.timeStamp - start_timestamp < 100) {
        showInfo('info_blocked');
      } else {
        showInfo('info_denied');
      }
      ignore_onend = true;
    }
  };

  recognition.onend = function() {
    recognizing = false;
    if (ignore_onend) {
      return;
    }
    start_img.src = '/intl/en/chrome/assets/common/images/content/mic.gif';
    if (!final_transcript) {
      showInfo('info_start');
      return;
    }
    showInfo('');
    if (window.getSelection) {
      window.getSelection().removeAllRanges();
      var range = document.createRange();
      range.selectNode(document.getElementById('final_span'));
      window.getSelection().addRange(range);
    }
    if (create_email) {
      create_email = false;
      createEmail();
    }
  };

  recognition.onresult = function(event) {
    var interim_transcript = '';
    if (typeof(event.results) == 'undefined') {
      recognition.onend = null;
      recognition.stop();
      upgrade();
      return;
    }
    for (var i = event.resultIndex; i < event.results.length; ++i) {
      if (event.results[i].isFinal) {
        final_transcript += event.results[i][0].transcript;
      } else {
        interim_transcript += event.results[i][0].transcript;
      }
    }
    final_transcript = capitalize(final_transcript);
    final_span.innerHTML = linebreak(final_transcript);
    interim_span.innerHTML = linebreak(interim_transcript);
    if (final_transcript || interim_transcript) {
      showButtons('inline-block');
    }
  };
}

function upgrade() {
  start_button.style.visibility = 'hidden';
  showInfo('info_upgrade');
}

var two_line = /\n\n/g;
var one_line = /\n/g;
function linebreak(s) {
  return s.replace(two_line, '<p></p>').replace(one_line, '<br>');
}

var first_char = /\S/;
function capitalize(s) {
  return s.replace(first_char, function(m) { return m.toUpperCase(); });
}

function createEmail() {
  var n = final_transcript.indexOf('\n');
  if (n < 0 || n >= 80) {
    n = 40 + final_transcript.substring(40).indexOf(' ');
  }
  var subject = encodeURI(final_transcript.substring(0, n));
  var body = encodeURI(final_transcript.substring(n + 1));
  window.location.href = 'mailto:?subject=' + subject + '&body=' + body;
}

function copyButton() {
  if (recognizing) {
    recognizing = false;
    recognition.stop();
  }
  copy_button.style.display = 'none';
  copy_info.style.display = 'inline-block';
  showInfo('');
}

function emailButton() {
  if (recognizing) {
    create_email = true;
    recognizing = false;
    recognition.stop();
  } else {
    createEmail();
  }
  email_button.style.display = 'none';
  email_info.style.display = 'inline-block';
  showInfo('');
}

function startButton(event) {
  if (recognizing) {
    recognition.stop();
    return;
  }
  final_transcript = '';
  recognition.lang = select_dialect.value;
  recognition.start();
  ignore_onend = false;
  final_span.innerHTML = '';
  interim_span.innerHTML = '';
  start_img.src = '/intl/en/chrome/assets/common/images/content/mic-slash.gif';
  showInfo('info_allow');
  showButtons('none');
  start_timestamp = event.timeStamp;
}

function showInfo(s) {
  if (s) {
    for (var child = info.firstChild; child; child = child.nextSibling) {
      if (child.style) {
        child.style.display = child.id == s ? 'inline' : 'none';
      }
    }
    info.style.visibility = 'visible';
  } else {
    info.style.visibility = 'hidden';
  }
}

var current_style;
function showButtons(style) {
  if (style == current_style) {
    return;
  }
  current_style = style;
  copy_button.style.display = style;
  email_button.style.display = style;
  copy_info.style.display = 'none';
  email_info.style.display = 'none';
}

attributed to authors of the document.

Though not certain how this affects the usage of SpeechSynthesisUtterance() and window.speechSynthesis.speak()?

How to load voices to populate window.speechSynthesis.getVoices()?

How does the linked demonstration document implement the functionality to transcribe voice to text?

What are the workarounds necessary to use the Web Speech API at chromium browser?

Specifically, how to transcribe voice to text and convert text to audio output?

Answer 1

Install espeak using package manager

$ sudo apt-get install espeak

Launch Chromium with --enable-speech-dispatcher flag

$ chromium-browser --enable-speech-dispatcher

Answer 2

2020. I recently tried to wrap my app which uses SpeechSynthesis with NWjs.

Properly works on Mac (mac os has voices by default).

As NWjs uses Chromium as a browser engine this proves that SpeechSynthesis works.

IMHO, the only difference between Chrome and Chromium that Chromium does not have Google voices and therefore will not work on the machine without voices installed.