I am using a wrapper of Web Speech API for Angular6. I am trying to implement a system of starting-stopping after each 3.5s in order to be able to manipulate the results for these small parts.
Even though I stop the recognition, before starting it again, I keep getting this error Failed to execute 'start' on 'SpeechRecognition': recognition has already started.
As suggested in this post, I first verify whether the speech recognition is active or not and only if not active, I try to start it. https://stackoverflow.com/a/44226843/6904971
Here is the code:
constructor( private http: Http, private service: SpeechRecognitionService, private links: LinksService) {
var recognizing; // will get bool values to verify if recognition is active
this.service.onresult = (e) => {
this.message = e.results[0].item(0).transcript;
};
this.service.onstart = function () {
recognizing = true;
};
this.service.onaudiostart = function () {
recognizing = true;
};
this.service.onerror = function (event) {
recognizing = false;
};
this.service.onsoundstart = function () {
recognizing = true;
};
this.service.onsoundstart = function () {
recognizing = true;
};
this.record = () => {
this.service.start();
setInterval(root.ongoing_recording(), 3500);
};
var root = this;
var speech = '';
this.stop_recording = () => {
this.service.stop();
};
this.ongoing_recording = ()=> {
setTimeout(function(){
if( recognizing === true){
root.service.stop();
root.service.onend = (e) => {
recognizing = false;
speech = root.message;
var sentence = document.createElement('span');
sentence.innerHTML = speech + " ";
document.body.appendChild(sentence);
}
}
}, 3500);
setTimeout(function(){
if(recognizing === false){
root.service.start();
}
}, 3510);
};
}
start() {
this.service.start();
}
stop() {
this.service.stop();
}
record(){
this.record();
}
stop_recording(){
this.stop_recording();
}
ongoing_recording(){
this.ongoing_recording();
}
I think that the timing might not be good (with the setTimeout and interval). Any help would be much appreciated. Thank you! :)
I used Web Speech API for voice search functionality in my site and I was facing a similar sort of situation. It has one microphone icon which toggles the speech recognition on and off. It was working fine in the normal on and off of the button that started speech recognition but was breaking only if you test it rigorously with a continuous button toggle.
Solution:
The thing that worked for me is:
try{
//line of code to start the speech recognition
}
catch{
//line of code to stop the speech recognition
}
So I wrapped the .start() method which was breaking the application in a try block and then added the catch block to stop it. And even if it comes across this problem, on the next button click to turn on the speech recognition, it works. I hope you would be able to extract something from it.
one observation:
you run setInterval() every 3500 ms to invoke ongoing_recording(), but then use setTimeout() with 3500 ms again within ongoing_recording().
Besides that, maybe logging the error handler --where recognizing is also set to false-- could help finding a solution:
in past versions of the SpeechRecognition implementation, not every error did actually stop the recognition (I don't know if that is still the case).
So it might be the case, that recognizing is reset due to an error that did not actually stop the recognition; if this is really the cause of the error when restarting recognition, it could be just catched & ignored.
Also it might be worth trying to re-start the recognition in the onend handler (and onerror).
I am not sure what is the reason that is causing it in your code, but i had the same error and what caused it in my case was that I was calling start() twice in a row, so what fixed it was adding a variable to check if the recognition has started or stopped, so if it has started and I clicked it again it would return speach.stop() to avoid using start() again.
let recognition = new SpeechRecognition();
let status = 0;
document.querySelector(".mic").addEventListener("click",() => {
if (status == 1) {
status = 0;
return recognition.stop();
}
recognition.start();
status = 1;
recognition.onresult = function (event) {
status=0;
var text = event.results[0][0].transcript;
recognition.stop();
};
recognition.onspeechend = function () {
status = 0;
recognition.stop();
};
});
Related
I've started to make a little speech recognition app
let loading = document.getElementById('loading')
let main = document.getElementById('main')
let speech = new webkitSpeechRecognition();
let isLoading = true
speech.addEventListener('error',(e)=>{
switch(e.error){
case 'not-allowed':
// Visual code here left out
break;
default:
console.error(e)
break;
}
})
speech.addEventListener('end',()=>{
speech.start();
})
function parseResult(result){
if(result.type == 'result'){
let text = result.results[result.resultIndex][0].transcript
// Visual code here left out
}
}
speech.onresult = parseResult;
speech.continuous = true;
speech.start();
And it works well once, then once I refresh it throws this every 5 seconds or so:
This is fixed by going to chrome://restart, but I would like it if users didn't have to restart their entire browser every time they went to the app.
Any idea of what's happening?
Following HTML shows empty array in console on first click:
<!DOCTYPE html>
<html>
<head>
<script>
function test(){
console.log(window.speechSynthesis.getVoices())
}
</script>
</head>
<body>
Test
</body>
</html>
In second click you will get the expected list.
If you add onload event to call this function (<body onload="test()">), then you can get correct result on first click. Note that the first call on onload still doesn't work properly. It returns empty on page load but works afterward.
Questions:
Since it might be a bug in beta version, I gave up on "Why" questions.
Now, the question is if you want to access window.speechSynthesis on page load:
What is the best hack for this issue?
How can you make sure it will load speechSynthesis, on page load?
Background and tests:
I was testing the new features in Web Speech API, then I got to this problem in my code:
<script type="text/javascript">
$(document).ready(function(){
// Browser support messages. (You might need Chrome 33.0 Beta)
if (!('speechSynthesis' in window)) {
alert("You don't have speechSynthesis");
}
var voices = window.speechSynthesis.getVoices();
console.log(voices) // []
$("#test").on('click', function(){
var voices = window.speechSynthesis.getVoices();
console.log(voices); // [SpeechSynthesisVoice, ...]
});
});
</script>
<a id="test" href="#">click here if 'ready()' didn't work</a>
My question was: why does window.speechSynthesis.getVoices() return empty array, after page is loaded and onready function is triggered? As you can see if you click on the link, same function returns an array of available voices of Chrome by onclick triger?
It seems Chrome loads window.speechSynthesis after the page load!
The problem is not in ready event. If I remove the line var voice=... from ready function, for first click it shows empty list in console. But the second click works fine.
It seems window.speechSynthesis needs more time to load after first call. You need to call it twice! But also, you need to wait and let it load before second call on window.speechSynthesis. For example, following code shows two empty arrays in console if you run it for first time:
// First speechSynthesis call
var voices = window.speechSynthesis.getVoices();
console.log(voices);
// Second speechSynthesis call
voices = window.speechSynthesis.getVoices();
console.log(voices);
According to Web Speech API Errata (E11 2013-10-17), the voice list is loaded async to the page. An onvoiceschanged event is fired when they are loaded.
voiceschanged: Fired when the contents of the SpeechSynthesisVoiceList, that the getVoices method will return, have changed. Examples include: server-side synthesis where the list is determined asynchronously, or when client-side voices are installed/uninstalled.
So, the trick is to set your voice from the callback for that event listener:
// wait on voices to be loaded before fetching list
window.speechSynthesis.onvoiceschanged = function() {
window.speechSynthesis.getVoices();
...
};
You can use a setInterval to wait until the voices are loaded before using them however you need and then clearing the setInterval:
var timer = setInterval(function() {
var voices = speechSynthesis.getVoices();
console.log(voices);
if (voices.length !== 0) {
var msg = new SpeechSynthesisUtterance(/*some string here*/);
msg.voice = voices[/*some number here to choose from array*/];
speechSynthesis.speak(msg);
clearInterval(timer);
}
}, 200);
$("#test").on('click', timer);
After studying the behavior on Google Chrome and Firefox, this is what can get all voices:
Since it involves something asynchronous, it might be best done with a promise:
const allVoicesObtained = new Promise(function(resolve, reject) {
let voices = window.speechSynthesis.getVoices();
if (voices.length !== 0) {
resolve(voices);
} else {
window.speechSynthesis.addEventListener("voiceschanged", function() {
voices = window.speechSynthesis.getVoices();
resolve(voices);
});
}
});
allVoicesObtained.then(voices => console.log("All voices:", voices));
Note:
When the event voiceschanged fires, we need to call .getVoices() again. The original array won't be populated with content.
On Google Chrome, we don't have to call getVoices() initially. We only need to listen on the event, and it will then happen. On Firefox, listening is not enough, you have to call getVoices() and then listen on the event voiceschanged, and set the array using getVoices() once you get notified.
Using a promise makes the code more clean. Everything related to getting voices are in this promise code. If you don't use a promise but instead put this code in your speech routine, it is quite messy.
You can write a voiceObtained promise to resolve to a voice you want, and then your function to say something can just do: voiceObtained.then(voice => { }) and inside that handler, call the window.speechSynthesis.speak() to speak something. Or you can even write a promise speechReady("hello world").then(speech => { window.speechSynthesis.speak(speech) }) to say something.
heres the answer
function synthVoice(text) {
const awaitVoices = new Promise(resolve=>
window.speechSynthesis.onvoiceschanged = resolve)
.then(()=> {
const synth = window.speechSynthesis;
var voices = synth.getVoices();
console.log(voices)
const utterance = new SpeechSynthesisUtterance();
utterance.voice = voices[3];
utterance.text = text;
synth.speak(utterance);
});
}
At first i used onvoiceschanged , but it kept firing even after the voices was loaded, so my goal was to avoid onvoiceschanged at all cost.
This is what i came up with. It seems to work so far, will update if it breaks.
loadVoicesWhenAvailable();
function loadVoicesWhenAvailable() {
voices = synth.getVoices();
if (voices.length !== 0) {
console.log("start loading voices");
LoadVoices();
}
else {
setTimeout(function () { loadVoicesWhenAvailable(); }, 10)
}
}
setInterval solution by Salman Oskooi was perfect
Please see https://jsfiddle.net/exrx8e1y/
function myFunction() {
dtlarea=document.getElementById("details");
//dtlarea.style.display="none";
dtltxt="";
var mytimer = setInterval(function() {
var voices = speechSynthesis.getVoices();
//console.log(voices);
if (voices.length !== 0) {
var msg = new SpeechSynthesisUtterance();
msg.rate = document.getElementById("rate").value; // 0.1 to 10
msg.pitch = document.getElementById("pitch").value; //0 to 2
msg.volume = document.getElementById("volume").value; // 0 to 1
msg.text = document.getElementById("sampletext").value;
msg.lang = document.getElementById("lang").value; //'hi-IN';
for(var i=0;i<voices.length;i++){
dtltxt+=voices[i].lang+' '+voices[i].name+'\n';
if(voices[i].lang==msg.lang) {
msg.voice = voices[i]; // Note: some voices don't support altering params
msg.voiceURI = voices[i].voiceURI;
// break;
}
}
msg.onend = function(e) {
console.log('Finished in ' + event.elapsedTime + ' seconds.');
dtlarea.value=dtltxt;
};
speechSynthesis.speak(msg);
clearInterval(mytimer);
}
}, 1000);
}
This works fine on Chrome for MAC, Linux(Ubuntu), Windows and Android
Android has non-standard en_GB wile others have en-GB as language code
Also you will see that same language(lang) has multiple names
On Mac Chrome you get en-GB Daniel besides en-GB Google UK English Female and n-GB Google UK English Male
en-GB Daniel (Mac and iOS)
en-GB Google UK English Female
en-GB Google UK English Male
en_GB English United Kingdom
hi-IN Google हिन्दी
hi-IN Lekha (Mac and iOS)
hi_IN Hindi India
Another way to ensure voices are loaded before you need them is to bind their loading state to a promise, and then dispatch your speech commands from a then:
const awaitVoices = new Promise(done => speechSynthesis.onvoiceschanged = done);
function listVoices() {
awaitVoices.then(()=> {
let voices = speechSynthesis.getVoices();
console.log(voices);
});
}
When you call listVoices, it will either wait for the voices to load first, or dispatch your operation on the next tick.
I used this code to load voices successfully:
<select id="voices"></select>
...
function loadVoices() {
populateVoiceList();
if (speechSynthesis.onvoiceschanged !== undefined) {
speechSynthesis.onvoiceschanged = populateVoiceList;
}
}
function populateVoiceList() {
var allVoices = speechSynthesis.getVoices();
allVoices.forEach(function(voice, index) {
var option = $('<option>').val(index).html(voice.name).prop("selected", voice.default);
$('#voices').append(option);
});
if (allVoices.length > 0 && speechSynthesis.onvoiceschanged !== undefined) {
// unregister event listener (it is fired multiple times)
speechSynthesis.onvoiceschanged = null;
}
}
I found the 'onvoiceschanged' code from this article: https://hacks.mozilla.org/2016/01/firefox-and-the-web-speech-api/
Note: requires JQuery.
Works in Firefox/Safari and Chrome (and in Google Apps Script too - but only in the HTML).
async function speak(txt) {
await initVoices();
const u = new SpeechSynthesisUtterance(txt);
u.voice = speechSynthesis.getVoices()[3];
speechSynthesis.speak(u);
}
function initVoices() {
return new Promise(function (res, rej){
speechSynthesis.getVoices();
if (window.speechSynthesis.onvoiceschanged) {
res();
} else {
window.speechSynthesis.onvoiceschanged = () => res();
}
});
}
While the accepted answer works great but if you're using SPA and not loading full-page, on navigating between links, the voices will not be available.
This will run on a full-page load
window.speechSynthesis.onvoiceschanged
For SPA, it wouldn't run.
You can check if it's undefined, run it, or else, get it from the window object.
An example that works:
let voices = [];
if(window.speechSynthesis.onvoiceschanged == undefined){
window.speechSynthesis.onvoiceschanged = () => {
voices = window.speechSynthesis.getVoices();
}
}else{
voices = window.speechSynthesis.getVoices();
}
// console.log("voices", voices);
I had to do my own research for this to make sure I understood it properly, so just sharing (feel free to edit).
My goal is to:
Get a list of voices available on my device
Populate a select element with those voices (after a particular page loads)
Use easy to understand code
The basic functionality is demonstrated in MDN's official live demo of:
https://github.com/mdn/web-speech-api/tree/master/speak-easy-synthesis
but I wanted to understand it better.
To break the topic down...
SpeechSynthesis
The SpeechSynthesis interface of the Web Speech API is the controller
interface for the speech service; this can be used to retrieve
information about the synthesis voices available on the device, start
and pause speech, and other commands besides.
Source
onvoiceschanged
The onvoiceschanged property of the SpeechSynthesis interface
represents an event handler that will run when the list of
SpeechSynthesisVoice objects that would be returned by the
SpeechSynthesis.getVoices() method has changed (when the voiceschanged
event fires.)
Source
Example A
If my application merely has:
var synth = window.speechSynthesis;
console.log(synth);
console.log(synth.onvoiceschanged);
Chrome developer tools console will show:
Example B
If I change the code to:
var synth = window.speechSynthesis;
console.log("BEFORE");
console.log(synth);
console.log(synth.onvoiceschanged);
console.log("AFTER");
var voices = synth.getVoices();
console.log(voices);
console.log(synth);
console.log(synth.onvoiceschanged);
The before and after states are the same, and voices is an empty array.
Solution
Although i'm not confident implementing Promises, the following worked for me:
Defining the function
var synth = window.speechSynthesis;
// declare so that values are accessible globally
var voices = [];
function set_up_speech() {
return new Promise(function(resolve, reject) {
// get the voices
var voices = synth.getVoices();
// get reference to select element
var $select_topic_speaking_voice = $("#select_topic_speaking_voice");
// for each voice, generate select option html and append to select
for (var i = 0; i < voices.length; i++) {
var option = $("<option></option>");
var suffix = "";
// if it is the default voice, add suffix text
if (voices[i].default) {
suffix = " -- DEFAULT";
}
// create the option text
var option_text = voices[i].name + " (" + voices[i].lang + suffix + ")";
// add the option text
option.text(option_text);
// add option attributes
option.attr("data-lang", voices[i].lang);
option.attr("data-name", voices[i].name);
// append option to select element
$select_topic_speaking_voice.append(option);
}
// resolve the voices value
resolve(voices)
});
}
Calling the function
// in your handler, populate the select element
if (page_title === "something") {
set_up_speech()
}
Android Chrome - turn off data saver. It was helpfull for me.(Chrome 71.0.3578.99)
// wait until the voices load
window.speechSynthesis.onvoiceschanged = function() {
window.speechSynthesis.getVoices();
};
let voices = speechSynthesis.getVoices();
let gotVoices = false;
if (voices.length) {
resolve(voices, message);
} else {
speechSynthesis.onvoiceschanged = () => {
if (!gotVoices) {
voices = speechSynthesis.getVoices();
gotVoices = true;
if (voices.length) resolve(voices, message);
}
};
}
function resolve(voices, message) {
var synth = window.speechSynthesis;
let utter = new SpeechSynthesisUtterance();
utter.lang = 'en-US';
utter.voice = voices[65];
utter.text = message;
utter.volume = 100.0;
synth.speak(utter);
}
Works for Edge, Chrome and Safari - doesn't repeat the sentences.
I am doing a POC and my requirement is that I want to implement the feature like OK google or Hey Siri on browser.
I am using the Chrome Browser's Web speech api. The things I noticed that I can't continuous the recognition as it terminates automatically after a certain period of time and I know its relevant because of security concern. I just does another hack like when the SpeechReognition terminates then on its end event I further start the SpeechRecogntion but it is not the best way to implement such a solution because suppose if I am using the 2 instances of same application on the different browser tab then It doesn't work or may be I am using another application in my browser that uses the speech recognition then both the application doesn't behave the same as expected. I am looking for a best approach to solve this problem.
Thanks in advance.
Since your problem is that you can't run the SpeechRecognition continuously for long periods of time, one way would be to start the SpeechRecognition only when you get some input in the mic.
This way only when there is some input, you will start the SR, looking for your magic_word.
If the magic_word is found, then you will be able to use the SR normally for your other tasks.
This can be detected by the WebAudioAPI, which is not tied by this time restriction SR suffers from. You can feed it by an LocalMediaStream from MediaDevices.getUserMedia.
For more info, on below script, you can see this answer.
Here is how you could attach it to a SpeechRecognition:
const magic_word = ##YOUR_MAGIC_WORD##;
// initialize our SpeechRecognition object
let recognition = new webkitSpeechRecognition();
recognition.lang = 'en-US';
recognition.interimResults = false;
recognition.maxAlternatives = 1;
recognition.continuous = true;
// detect the magic word
recognition.onresult = e => {
// extract all the transcripts
var transcripts = [].concat.apply([], [...e.results]
.map(res => [...res]
.map(alt => alt.transcript)
)
);
if(transcripts.some(t => t.indexOf(magic_word) > -1)){
//do something awesome, like starting your own command listeners
}
else{
// didn't understood...
}
}
// called when we detect silence
function stopSpeech(){
recognition.stop();
}
// called when we detect sound
function startSpeech(){
try{ // calling it twice will throw...
recognition.start();
}
catch(e){}
}
// request a LocalMediaStream
navigator.mediaDevices.getUserMedia({audio:true})
// add our listeners
.then(stream => detectSilence(stream, stopSpeech, startSpeech))
.catch(e => log(e.message));
function detectSilence(
stream,
onSoundEnd = _=>{},
onSoundStart = _=>{},
silence_delay = 500,
min_decibels = -80
) {
const ctx = new AudioContext();
const analyser = ctx.createAnalyser();
const streamNode = ctx.createMediaStreamSource(stream);
streamNode.connect(analyser);
analyser.minDecibels = min_decibels;
const data = new Uint8Array(analyser.frequencyBinCount); // will hold our data
let silence_start = performance.now();
let triggered = false; // trigger only once per silence event
function loop(time) {
requestAnimationFrame(loop); // we'll loop every 60th of a second to check
analyser.getByteFrequencyData(data); // get current data
if (data.some(v => v)) { // if there is data above the given db limit
if(triggered){
triggered = false;
onSoundStart();
}
silence_start = time; // set it to now
}
if (!triggered && time - silence_start > silence_delay) {
onSoundEnd();
triggered = true;
}
}
loop();
}
As a plunker, since neither StackSnippets nor jsfiddle's iframes will allow gUM in two versions...
I've been using the W3C Speech Synthesizer for the web in my app. I'd like the words to start appearing as I speak them. This is because I want the user to have near-instant feedback on the current word they're speaking. Currently, the result events in the spec wait to append the entire array after a second or so of not speaking.
I've looked through the standards, but I've only found that it waits a bit to construct the final results list from the result event:
5.1.3 SpeechRecognition Events
result event: Fired when the speech recognizer returns a result
5.1.8 SpeechRecognitionEvent
results attribute: The array of all current recognition results for this session.
I've also tried retrieving the results in onstart and onpause methods:
recognition = new webkitSpeechRecognition()
recognition.onstart = function (event) {
//append word
};
recognition.onpause = function (event) {
//append word
};
Anyone know a way to accomplish this "typing" effect of the words as you speak?
The other issue is, if the user stops speaking for a sec, and the results list is compiled (IE, the result event is fired), and they go to speak again, the results list is not updated.
This happens even if I set recognition.continuous = true;
Found it from Google Developers Introduction Video.
In addition to recognition.continuous = true, you also need recognition.interimResults = true;.
Then need to modify your logic slightly in the onresult handler to account for interim results:
recognition.onresult = function (event) {
var final = "";
var interim = "";
for (var i = 0; i < event.results.length; ++i) {
if (event.results[i].final) {
final += event.results[i][0].transcript;
} else {
interim += event.results[i][0].transcript;
}
}
final_span.innerHTML = final;
interim_span.innerHTML = interim;
}
I often read that it's not possible to pause/resume audio files with the Web Audio API.
But now I saw a example where they actually made it possible to pause and resume it. I tried to figure out what how they did it. I thought maybe source.looping = falseis the key, but it wasn't.
For now my audio is always re-playing from the start.
This is my current code
var context = new (window.AudioContext || window.webkitAudioContext)();
function AudioPlayer() {
this.source = context.createBufferSource();
this.analyser = context.createAnalyser();
this.stopped = true;
}
AudioPlayer.prototype.setBuffer = function(buffer) {
this.source.buffer = buffer;
this.source.looping = false;
};
AudioPlayer.prototype.play = function() {
this.source.connect(this.analyser);
this.analyser.connect(context.destination);
this.source.noteOn(0);
this.stopped = false;
};
AudioPlayer.prototype.stop = function() {
this.analyser.disconnect();
this.source.disconnect();
this.stopped = true;
};
Does anybody know what to do, to get it work?
Oskar's answer and ayke's comment are very helpful, but I was missing a code example. So I wrote one: http://jsfiddle.net/v3syS/2/ I hope it helps.
var url = 'http://thelab.thingsinjars.com/web-audio-tutorial/hello.mp3';
var ctx = new webkitAudioContext();
var buffer;
var sourceNode;
var startedAt;
var pausedAt;
var paused;
function load(url) {
var request = new XMLHttpRequest();
request.open('GET', url, true);
request.responseType = 'arraybuffer';
request.onload = function() {
ctx.decodeAudioData(request.response, onBufferLoad, onBufferError);
};
request.send();
};
function play() {
sourceNode = ctx.createBufferSource();
sourceNode.connect(ctx.destination);
sourceNode.buffer = buffer;
paused = false;
if (pausedAt) {
startedAt = Date.now() - pausedAt;
sourceNode.start(0, pausedAt / 1000);
}
else {
startedAt = Date.now();
sourceNode.start(0);
}
};
function stop() {
sourceNode.stop(0);
pausedAt = Date.now() - startedAt;
paused = true;
};
function onBufferLoad(b) {
buffer = b;
play();
};
function onBufferError(e) {
console.log('onBufferError', e);
};
document.getElementById("toggle").onclick = function() {
if (paused) play();
else stop();
};
load(url);
In current browsers (Chrome 43, Firefox 40) there are now 'suspend' and 'resume' methods available for AudioContext:
var audioCtx = new AudioContext();
susresBtn.onclick = function() {
if(audioCtx.state === 'running') {
audioCtx.suspend().then(function() {
susresBtn.textContent = 'Resume context';
});
} else if(audioCtx.state === 'suspended') {
audioCtx.resume().then(function() {
susresBtn.textContent = 'Suspend context';
});
}
}
(modified example code from https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/suspend)
Actually the web-audio API can do the pause and play task for you. It knows the current state of the audio context (running or suspended), so you can do this in this easy way:
susresBtn.onclick = function() {
if(audioCtx.state === 'running') {
audioCtx.suspend()
} else if(audioCtx.state === 'suspended') {
audioCtx.resume()
}
}
I hope this can help.
Without spending any time checking the source of your example, I'd say you'll want to use the noteGrainOn method of the AudioBufferSourceNode (https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#methodsandparams-AudioBufferSourceNode)
Just keep track of how far into the buffer you were when you called noteOff, and then do noteGrainOn from there when resuming on a new AudioBufferSourceNode.
Did that make sense?
EDIT:
See comments below for updated API calls.
EDIT 2, 2019: See MDN for updated API calls; https://developer.mozilla.org/en-US/docs/Web/API/AudioBufferSourceNode/start
For chrome fix, every time you want to play sound, set it like:
if(audioCtx.state === 'suspended') {
audioCtx.resume().then(function() {
audio.play();
});
}else{
audio.play();
}
The lack of a built-in pause functionality in the WebAudio API seems like a major oversight to me. Possibly, in the future it will be possible to do this using the planned MediaElementSource, which will let you hook up an element (which supports pausing) to Web Audio. For now, most workarounds seem to be based on remembering playback time (such as described in imbrizi's answer). Such a workaround has issues when looping sounds (does the implementation loop gapless or not?), and when you allow dynamically change the playbackRate of sounds (as both affect timing). Another, equally hack-ish and technically incorrect, but much simpler workaround you can use is:
source.playbackRate = paused?0.0000001:1;
Unfortunately, 0 is not a valid value for playbackRate (which would actually pause the sound). However, for many practical purposes, some very low value, like 0.000001, is close enough, and it won't produce any audible output.
UPDATE: This is only valid for Chrome. Firefox (v29) does not yet implement the MediaElementAudioSourceNode.mediaElement property.
Assuming that you already have the AudioContext reference and your media source (e.g. via AudioContext.createMediaElementSource() method call), you can call MediaElement.play() and MediaElement.pause()on your source, e.g.
source.mediaElement.pause();
source.mediaElement.play();
No need for hacks and workarounds, it's supported.
If you are working with an <audio> tag as your source, you should not call pause directly on the audio element in your JavaScript, that will stop playback.
In 2017, using ctx.currentTime works well for keeping track of the point in the song. The code below uses one button (songStartPause) that toggles between a play & pause button. I used global variables for simplicity's sake. The variable musicStartPoint keeps track of what time you're at in the song. The music api keeps track of time in seconds.
Set your initial musicStartPoint at 0 (beginning of the song)
var ctx = new webkitAudioContext();
var buff, src;
var musicLoaded = false;
var musicStartPoint = 0;
var songOnTime, songEndTime;
var songOn = false;
songStartPause.onclick = function() {
if(!songOn) {
if(!musicLoaded) {
loadAndPlay();
musicLoaded = true;
} else {
play();
}
songOn = true;
songStartPause.innerHTML = "||" //a fancy Pause symbol
} else {
songOn = false;
src.stop();
setPausePoint();
songStartPause.innerHTML = ">" //a fancy Play symbol
}
}
Use ctx.currentTime to subtract the time the song ends from when it started, and append this length of time to however far you were in the song initially.
function setPausePoint() {
songEndTime = ctx.currentTime;
musicStartPoint += (songEndTime - songOnTime);
}
Load/play functions.
function loadAndPlay() {
var req = new XMLHttpRequest();
req.open("GET", "//mymusic.com/unity.mp3")
req.responseType = "arraybuffer";
req.onload = function() {
ctx.decodeAudioData(req.response, function(buffer) {
buff = buffer;
play();
})
}
req.send();
}
function createBuffer() {
src = ctx.createBufferSource();
src.buffer = buff;
}
function connectNodes() {
src.connect(ctx.destination);
}
Lastly, the play function tells the song to start at the specified musicStartPoint (and to play it immediately), and also sets the songOnTime variable.
function play(){
createBuffer()
connectNodes();
songOnTime = ctx.currentTime;
src.start(0, musicStartPoint);
}
*Sidenote: I know it might look cleaner to set songOnTime up in the click function, but I figure it makes sense to grab the time code as close as possible to src.start, just like how we grab the pause time as close as possible to src.stop.
I didn't follow the full discussion, but I will soon. I simply headed over HAL demo to understand. For those who now do like me, I would like to tell
1 - how to make this code working now.
2 - a trick to get pause/play, from this code.
1 : replace noteOn(xx) with start(xx) and put any valid url in sound.load(). I think it's all I've done. You will get a few errors in the console that are pretty directive. Follow them. Or not : sometimes you can ignore them, it works now : it's related to the -webkit prefix in some function. New ones are given.
2 : at some point, when it works, you may want to pause the sound.
It will work. But, as everybody knows, a new pressing on play would raise an error. As a result, the code in this.play() after the faulty source_.start(0) is not executed.
I simply enclosed those line in a try/catch :
this.play = function() {
analyser_ = context_.createAnalyser();
// Connect the processing graph: source -> analyser -> destination
source_.connect(analyser_);
analyser_.connect(context_.destination);
try{
source_.start(0);
}
catch(e){
this.playing = true;
(function callback(time) {
processAudio_(time);
reqId_ = window.webkitRequestAnimationFrame(callback);
})();
}
And it works : you can use play/pause.
I would like to mention that this HAL simulation is really incredible. Follow those simple steps, it's worth it !