I’m trying to integrate the Whisper.cpp stream web demo into my SvelteKit project for local browser-based speech recognition. I’ve analyzed their implementation which uses WebAssembly with a worker thread setup.
The original implementation consists of several key files:
stream.js: This is the core file that manages WebAssembly (WASM) functionality. It handles memory management, file system operations, and provides the interface between JavaScript and the compiled C/C++ code. It’s responsible for initializing the WASM module and managing its runtime environment.index.html: This is the main entry point of the application that provides the user interface and core browser functionality. It contains the UI elements, manages the application’s cache through IndexedDB, handles file uploads and downloads, and coordinates communication between different parts of the application.libstream.worker.js: This is a Web Worker script that runs in a separate thread from the main UI. It handles computationally intensive tasks to prevent the main interface from becoming unresponsive. It’s designed to work in both browser and Node.js environments and manages thread-specific operations and message passing.server.py: A simple Python-based HTTP server that serves the application files and handles Cross-Origin Resource Sharing (CORS) headers. This enables the necessary permissions for WebAssembly to function properly and allows the application to make requests for resources across different origins.
I have tried using the same structure in SvelteKit, moving stream.js and libstream.worker.js to /static and and replacing /src/app.html with my index.html file, but adding %sveltekit.head% to the head and <body data-sveltekit-preload-data="hover"> <div style="display: contents">%sveltekit.body%</div> to the top of the body. disabled ssr rendering with src/routes/+page.ts: export const ssr = false;. Finally, I added src/hooks.server.ts:
import type { Handle } from "@sveltejs/kit";
export const handle: Handle = async ({ event, resolve }) => {
const response = await resolve(event);
// Add security headers
response.headers.set("Cross-Origin-Opener-Policy", "same-origin");
response.headers.set("Cross-Origin-Embedder-Policy", "require-corp");
return response;
};
When I try running my code using pnpm dev and navigate to localhost:5173, I get the following error in the browser console:
One potential reason for my error is that the web worker does not start. In the pure HTML project hosted with python, I see several libstream.worker.js in the sources tab of the dev tools, but I do not see these in my sveltekit implementation.
How can I fix this so that I am able to run the wasm-version of whisper.cpp in browser?
Part of stream.js where the error is thrown. It is thrown in the worker.onerror part.
loadWasmModuleToWorker: function(worker, onFinishedLoading) {
worker.onmessage = e => {
var d = e["data"];
var cmd = d["cmd"];
if (worker.pthread_ptr)
PThread.currentProxiedOperationCallerThread = worker.pthread_ptr;
if (d["targetThread"] && d["targetThread"] != _pthread_self()) {
var targetWorker = PThread.pthreads[d.targetThread];
if (targetWorker) {
targetWorker.postMessage(d, d["transferList"])
} else {
err('Internal error! Worker sent a message "' + cmd + '" to target pthread ' + d["targetThread"] + ", but that thread no longer exists!")
}
PThread.currentProxiedOperationCallerThread = undefined;
return
}
if (cmd === "processProxyingQueue") {
executeNotifiedProxyingQueue(d["queue"])
} else if (cmd === "spawnThread") {
spawnThread(d)
} else if (cmd === "cleanupThread") {
cleanupThread(d["thread"])
} else if (cmd === "killThread") {
killThread(d["thread"])
} else if (cmd === "cancelThread") {
cancelThread(d["thread"])
} else if (cmd === "loaded") {
worker.loaded = true;
if (ENVIRONMENT_IS_NODE) {}
if (onFinishedLoading)
onFinishedLoading(worker);
if (worker.runPthread) {
worker.runPthread()
}
} else if (cmd === "print") {
out("Thread " + d["threadId"] + ": " + d["text"])
} else if (cmd === "printErr") {
err("Thread " + d["threadId"] + ": " + d["text"])
} else if (cmd === "alert") {
alert("Thread " + d["threadId"] + ": " + d["text"])
} else if (d.target === "setimmediate") {
worker.postMessage(d)
} else if (cmd === "callHandler") {
Module[d["handler"]](...d["args"])
} else if (cmd) {
err("worker sent an unknown command " + cmd)
}
PThread.currentProxiedOperationCallerThread = undefined
}
;
worker.onerror = e => {
var message = "worker sent an error!";
err(message + " " + e.filename + ":" + e.lineno + ": " + e.message);
throw e
}
;
if (ENVIRONMENT_IS_NODE) {}
var handlers = [];
var knownHandlers = ["onExit", "onAbort", "print", "printErr"];
for (var handler of knownHandlers) {
if (Module.hasOwnProperty(handler)) {
handlers.push(handler)
}
}
worker.postMessage({
"cmd": "load",
"handlers": handlers,
"urlOrBlob": Module["mainScriptUrlOrBlob"] || _scriptDir,
"wasmMemory": wasmMemory,
"wasmModule": wasmModule
})
},
Original files:
<!doctype html>
<html lang="en-us">
<body>
<div id="model-whisper">
<span id="model-whisper-status"></span>
<button id="fetch-whisper-base-en-q5_1" onclick="loadWhisper('base-en-q5_1')">base.en (Q5_1, 57 MB)</button>
<span id="fetch-whisper-progress"></span>
</div>
<div id="input">
<button id="start" onclick="onStart()" disabled>Start</button>
<button id="stop" onclick="onStop()" disabled>Stop</button>
</div>
<br>
<div id="state">
<span id="state-status">not started</span></b>
<pre id="state-transcribed">[The transcribed text will be displayed here]</pre>
</div>
<textarea id="output" rows="20"></textarea>
<script type="text/javascript">
// Common Javascript functions used by the examples
function convertTypedArray(src, type) {
var buffer = new ArrayBuffer(src.byteLength);
var baseView = new src.constructor(buffer).set(src);
return new type(buffer);
}
var printTextarea = (function() {
var element = document.getElementById('output');
if (element) element.value = ''; // clear browser cache
return function(text) {
if (arguments.length > 1) text = Array.prototype.slice.call(arguments).join(' ');
console.log(text);
if (element) {
element.value += text + "n";
element.scrollTop = element.scrollHeight; // focus on bottom
}
};
})();
async function clearCache() {
if (confirm('Are you sure you want to clear the cache?nAll the models will be downloaded again.')) {
indexedDB.deleteDatabase(dbName);
}
}
// fetch a remote file from remote URL using the Fetch API
async function fetchRemote(url, cbProgress, cbPrint) {
cbPrint('fetchRemote: downloading with fetch()...');
const response = await fetch(
url,
{
method: 'GET',
headers: {
'Content-Type': 'application/octet-stream',
},
}
);
if (!response.ok) {
cbPrint('fetchRemote: failed to fetch ' + url);
return;
}
const contentLength = response.headers.get('content-length');
const total = parseInt(contentLength, 10);
const reader = response.body.getReader();
var chunks = [];
var receivedLength = 0;
var progressLast = -1;
while (true) {
const { done, value } = await reader.read();
if (done) {
break;
}
chunks.push(value);
receivedLength += value.length;
if (contentLength) {
cbProgress(receivedLength/total);
var progressCur = Math.round((receivedLength / total) * 10);
if (progressCur != progressLast) {
cbPrint('fetchRemote: fetching ' + 10*progressCur + '% ...');
progressLast = progressCur;
}
}
}
var position = 0;
var chunksAll = new Uint8Array(receivedLength);
for (var chunk of chunks) {
chunksAll.set(chunk, position);
position += chunk.length;
}
return chunksAll;
}
// load remote data
// - check if the data is already in the IndexedDB
// - if not, fetch it from the remote URL and store it in the IndexedDB
function loadRemote(url, dst, size_mb, cbProgress, cbReady, cbCancel, cbPrint) {
if (!navigator.storage || !navigator.storage.estimate) {
cbPrint('loadRemote: navigator.storage.estimate() is not supported');
} else {
// query the storage quota and print it
navigator.storage.estimate().then(function (estimate) {
cbPrint('loadRemote: storage quota: ' + estimate.quota + ' bytes');
cbPrint('loadRemote: storage usage: ' + estimate.usage + ' bytes');
});
}
// check if the data is already in the IndexedDB
var rq = indexedDB.open(dbName, dbVersion);
rq.onupgradeneeded = function (event) {
var db = event.target.result;
if (db.version == 1) {
var os = db.createObjectStore('models', { autoIncrement: false });
cbPrint('loadRemote: created IndexedDB ' + db.name + ' version ' + db.version);
} else {
// clear the database
var os = event.currentTarget.transaction.objectStore('models');
os.clear();
cbPrint('loadRemote: cleared IndexedDB ' + db.name + ' version ' + db.version);
}
};
rq.onsuccess = function (event) {
var db = event.target.result;
var tx = db.transaction(['models'], 'readonly');
var os = tx.objectStore('models');
var rq = os.get(url);
rq.onsuccess = function (event) {
if (rq.result) {
cbPrint('loadRemote: "' + url + '" is already in the IndexedDB');
cbReady(dst, rq.result);
} else {
// data is not in the IndexedDB
cbPrint('loadRemote: "' + url + '" is not in the IndexedDB');
// alert and ask the user to confirm
if (!confirm(
'You are about to download ' + size_mb + ' MB of data.n' +
'The model data will be cached in the browser for future use.nn' +
'Press OK to continue.')) {
cbCancel();
return;
}
fetchRemote(url, cbProgress, cbPrint).then(function (data) {
if (data) {
// store the data in the IndexedDB
var rq = indexedDB.open(dbName, dbVersion);
rq.onsuccess = function (event) {
var db = event.target.result;
var tx = db.transaction(['models'], 'readwrite');
var os = tx.objectStore('models');
var rq = null;
try {
var rq = os.put(data, url);
} catch (e) {
cbPrint('loadRemote: failed to store "' + url + '" in the IndexedDB: n' + e);
cbCancel();
return;
}
rq.onsuccess = function (event) {
cbPrint('loadRemote: "' + url + '" stored in the IndexedDB');
cbReady(dst, data);
};
rq.onerror = function (event) {
cbPrint('loadRemote: failed to store "' + url + '" in the IndexedDB');
cbCancel();
};
};
}
});
}
};
rq.onerror = function (event) {
cbPrint('loadRemote: failed to get data from the IndexedDB');
cbCancel();
};
};
rq.onerror = function (event) {
cbPrint('loadRemote: failed to open IndexedDB');
cbCancel();
};
rq.onblocked = function (event) {
cbPrint('loadRemote: failed to open IndexedDB: blocked');
cbCancel();
};
rq.onabort = function (event) {
cbPrint('loadRemote: failed to open IndexedDB: abort');
cbCancel();
};
}
</script>
<script type='text/javascript'>
// web audio context
var context = null;
// audio data
var audio = null;
var audio0 = null;
// the stream instance
var instance = null;
// model name
var model_whisper = null;
var Module = {
print: printTextarea,
printErr: printTextarea,
setStatus: function(text) {
printTextarea('js: ' + text);
},
monitorRunDependencies: function(left) {
},
preRun: function() {
printTextarea('js: Preparing ...');
},
postRun: function() {
printTextarea('js: Initialized successfully!');
}
};
//
// fetch models
//
let dbVersion = 1
let dbName = 'whisper.ggerganov.com';
let indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB
function storeFS(fname, buf) {
// write to WASM file using FS_createDataFile
// if the file exists, delete it
try {
Module.FS_unlink(fname);
} catch (e) {
// ignore
}
Module.FS_createDataFile("/", fname, buf, true, true);
printTextarea('storeFS: stored model: ' + fname + ' size: ' + buf.length);
document.getElementById('model-whisper-status').innerHTML = 'loaded "' + model_whisper + '"!';
if (model_whisper != null) {
document.getElementById('start').disabled = false;
document.getElementById('stop' ).disabled = true;
}
}
function loadWhisper(model) {
let urls = {
'base-en-q5_1': '/models/ggml-model-whisper-base.en-q5_1.bin',
};
let sizes = {
'base-en-q5_1': 57,
};
let url = urls[model];
let dst = 'whisper.bin';
let size_mb = sizes[model];
model_whisper = model;
document.getElementById('fetch-whisper-base-en-q5_1').style.display = 'none';
document.getElementById('model-whisper-status').innerHTML = 'loading "' + model + '" ... ';
cbProgress = function(p) {
let el = document.getElementById('fetch-whisper-progress');
el.innerHTML = Math.round(100*p) + '%';
};
cbCancel = function() {
var el;
el = document.getElementById('fetch-whisper-base-en-q5_1'); if (el) el.style.display = 'inline-block';
el = document.getElementById('model-whisper-status'); if (el) el.innerHTML = '';
};
loadRemote(url, dst, size_mb, cbProgress, storeFS, cbCancel, printTextarea);
}
//
// microphone
//
const kSampleRate = 16000;
const kRestartRecording_s = 120;
const kIntervalAudio_ms = 5000; // pass the recorded audio to the C++ instance at this rate
var mediaRecorder = null;
var doRecording = false;
var startTime = 0;
window.AudioContext = window.AudioContext || window.webkitAudioContext;
window.OfflineAudioContext = window.OfflineAudioContext || window.webkitOfflineAudioContext;
function stopRecording() {
Module.set_status("paused");
doRecording = false;
audio0 = null;
audio = null;
context = null;
}
function startRecording() {
if (!context) {
context = new AudioContext({
sampleRate: kSampleRate,
channelCount: 1,
echoCancellation: false,
autoGainControl: true,
noiseSuppression: true,
});
}
Module.set_status("");
document.getElementById('start').disabled = true;
document.getElementById('stop').disabled = false;
doRecording = true;
startTime = Date.now();
var chunks = [];
var stream = null;
navigator.mediaDevices.getUserMedia({audio: true, video: false})
.then(function(s) {
stream = s;
mediaRecorder = new MediaRecorder(stream);
mediaRecorder.ondataavailable = function(e) {
chunks.push(e.data);
var blob = new Blob(chunks, { 'type' : 'audio/ogg; codecs=opus' });
var reader = new FileReader();
reader.onload = function(event) {
var buf = new Uint8Array(reader.result);
if (!context) {
return;
}
context.decodeAudioData(buf.buffer, function(audioBuffer) {
var offlineContext = new OfflineAudioContext(audioBuffer.numberOfChannels, audioBuffer.length, audioBuffer.sampleRate);
var source = offlineContext.createBufferSource();
source.buffer = audioBuffer;
source.connect(offlineContext.destination);
source.start(0);
offlineContext.startRendering().then(function(renderedBuffer) {
audio = renderedBuffer.getChannelData(0);
//printTextarea('js: audio recorded, size: ' + audio.length + ', old size: ' + (audio0 == null ? 0 : audio0.length));
var audioAll = new Float32Array(audio0 == null ? audio.length : audio0.length + audio.length);
if (audio0 != null) {
audioAll.set(audio0, 0);
}
audioAll.set(audio, audio0 == null ? 0 : audio0.length);
if (instance) {
Module.set_audio(instance, audioAll);
}
});
}, function(e) {
audio = null;
});
}
reader.readAsArrayBuffer(blob);
};
mediaRecorder.onstop = function(e) {
if (doRecording) {
setTimeout(function() {
startRecording();
});
}
};
mediaRecorder.start(kIntervalAudio_ms);
})
.catch(function(err) {
printTextarea('js: error getting audio stream: ' + err);
});
var interval = setInterval(function() {
if (!doRecording) {
clearInterval(interval);
mediaRecorder.stop();
stream.getTracks().forEach(function(track) {
track.stop();
});
document.getElementById('start').disabled = false;
document.getElementById('stop').disabled = true;
mediaRecorder = null;
}
// if audio length is more than kRestartRecording_s seconds, restart recording
if (audio != null && audio.length > kSampleRate*kRestartRecording_s) {
if (doRecording) {
//printTextarea('js: restarting recording');
clearInterval(interval);
audio0 = audio;
audio = null;
mediaRecorder.stop();
stream.getTracks().forEach(function(track) {
track.stop();
});
}
}
}, 100);
}
//
// main
//
var nLines = 0;
var intervalUpdate = null;
var transcribedAll = '';
function onStart() {
if (!instance) {
instance = Module.init('whisper.bin');
if (instance) {
printTextarea("js: whisper initialized, instance: " + instance);
}
}
if (!instance) {
printTextarea("js: failed to initialize whisper");
return;
}
startRecording();
intervalUpdate = setInterval(function() {
var transcribed = Module.get_transcribed();
if (transcribed != null && transcribed.length > 1) {
transcribedAll += transcribed + '<br>';
nLines++;
// if more than 10 lines, remove the first line
if (nLines > 10) {
var i = transcribedAll.indexOf('<br>');
if (i > 0) {
transcribedAll = transcribedAll.substring(i + 4);
nLines--;
}
}
}
document.getElementById('state-status').innerHTML = Module.get_status();
document.getElementById('state-transcribed').innerHTML = transcribedAll;
}, 100);
}
function onStop() {
stopRecording();
}
</script>
<script type="text/javascript" src="stream.js"></script>
</body>
</html>
"use strict";
var Module = {};
var ENVIRONMENT_IS_NODE =
typeof process == "object" &&
typeof process.versions == "object" &&
typeof process.versions.node == "string";
if (ENVIRONMENT_IS_NODE) {
var nodeWorkerThreads = require("worker_threads");
var parentPort = nodeWorkerThreads.parentPort;
parentPort.on("message", (data) =>
onmessage({
data: data,
})
);
var fs = require("fs");
Object.assign(global, {
self: global,
require: require,
Module: Module,
location: {
href: __filename,
},
Worker: nodeWorkerThreads.Worker,
importScripts: function (f) {
(0, eval)(fs.readFileSync(f, "utf8") + "//# sourceURL=" + f);
},
postMessage: function (msg) {
parentPort.postMessage(msg);
},
performance: global.performance || {
now: function () {
return Date.now();
},
},
});
}
var initializedJS = false;
var pendingNotifiedProxyingQueues = [];
function threadPrintErr() {
var text = Array.prototype.slice.call(arguments).join(" ");
if (ENVIRONMENT_IS_NODE) {
fs.writeSync(2, text + "n");
return;
}
console.error(text);
}
function threadAlert() {
var text = Array.prototype.slice.call(arguments).join(" ");
postMessage({
cmd: "alert",
text: text,
threadId: Module["_pthread_self"](),
});
}
var err = threadPrintErr;
self.alert = threadAlert;
Module["instantiateWasm"] = (info, receiveInstance) => {
var instance = new WebAssembly.Instance(Module["wasmModule"], info);
receiveInstance(instance);
Module["wasmModule"] = null;
return instance.exports;
};
self.onunhandledrejection = (e) => {
throw e.reason ?? e;
};
self.onmessage = (e) => {
try {
if (e.data.cmd === "load") {
Module["wasmModule"] = e.data.wasmModule;
for (const handler of e.data.handlers) {
Module[handler] = function () {
postMessage({
cmd: "callHandler",
handler: handler,
args: [...arguments],
});
};
}
Module["wasmMemory"] = e.data.wasmMemory;
Module["buffer"] = Module["wasmMemory"].buffer;
Module["ENVIRONMENT_IS_PTHREAD"] = true;
if (typeof e.data.urlOrBlob == "string") {
importScripts(e.data.urlOrBlob);
} else {
var objectUrl = URL.createObjectURL(e.data.urlOrBlob);
importScripts(objectUrl);
URL.revokeObjectURL(objectUrl);
}
} else if (e.data.cmd === "run") {
Module["__performance_now_clock_drift"] = performance.now() - e.data.time;
Module["__emscripten_thread_init"](e.data.pthread_ptr, 0, 0, 1);
Module["establishStackSpace"]();
Module["PThread"].receiveObjectTransfer(e.data);
Module["PThread"].threadInitTLS();
if (!initializedJS) {
Module["__embind_initialize_bindings"]();
pendingNotifiedProxyingQueues.forEach((queue) => {
Module["executeNotifiedProxyingQueue"](queue);
});
pendingNotifiedProxyingQueues = [];
initializedJS = true;
}
try {
Module["invokeEntryPoint"](e.data.start_routine, e.data.arg);
} catch (ex) {
if (ex != "unwind") {
if (ex instanceof Module["ExitStatus"]) {
if (Module["keepRuntimeAlive"]()) {
} else {
Module["__emscripten_thread_exit"](ex.status);
}
} else {
throw ex;
}
}
}
} else if (e.data.cmd === "cancel") {
if (Module["_pthread_self"]()) {
Module["__emscripten_thread_exit"](-1);
}
} else if (e.data.target === "setimmediate") {
} else if (e.data.cmd === "processProxyingQueue") {
if (initializedJS) {
Module["executeNotifiedProxyingQueue"](e.data.queue);
} else {
pendingNotifiedProxyingQueues.push(e.data.queue);
}
} else if (e.data.cmd) {
err("worker.js received unknown command " + e.data.cmd);
err(e.data);
}
} catch (ex) {
if (Module["__emscripten_thread_crashed"]) {
Module["__emscripten_thread_crashed"]();
}
throw ex;
}
};
Full code dump including the 5000 line stream.js: https://gist.github.com/vlashada/445169a9d543e973cc5813d2ec3f2ed1
I have tried my very best to include everything relevant and to make the examples as minimal as possible, but please let me know if I can do anything more to increase clarity.