Как использовать Web Speech API в Chrome?

Как использовать SpeechSynthesisUtterance() и window.speechSynthesis.speak() в браузере Chrome?

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

не выводит звук на системные динамики.

Были отмечены проблемы с API. HTML5 SpeechSynthesis API - мусор;

var voices = window.speechSynthesis.getVoices();

записывает пустой массив для идентификатора voices; и только хром, но не хром, якобы поддерживает спецификацию Web Speech API Specification, Web Speech API Demonstration устанавливает значение html element при демонстрации высказывания, озвученного при включенном микрофоне на странице.

По крайней мере, часть кода JavaScript, относящегося к функциональности, очевидно

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';
}

приписывается авторам документа.

Хотя не уверены, как это влияет на использование SpeechSynthesisUtterance() и window.speechSynthesis.speak()?

Как загрузить голоса для заполнения window.speechSynthesis.getVoices()?

Как связанный демонстрационный документ реализует функцию преобразования голоса в текст?

Какие обходные пути необходимы для использования Web Speech API в браузере Chrome?

В частности, как преобразовать голос в текст и преобразовать текст в аудиовыход?