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convert audio buffer to play as audio element

I'm using the souncloud api to stream audio from soundcloud. However, I'm trying to get the tracks BPM programmatically so I have the following
Soundcloud.prototype.play = function (options) {
options = options || {};
var src;
if (options.streamUrl) {
src = options.streamUrl;
} else if (this._playlist) {
var length = this._playlist.tracks.length;
if (length) {
if (options.playlistIndex === undefined) {
this._playlistIndex = this._playlistIndex || 0;
} else {
this._playlistIndex = options.playlistIndex;
}
// be silent if index is out of range
if (this._playlistIndex >= length || this._playlistIndex < 0) {
this._playlistIndex = 0;
return;
}
src = this._playlist.tracks[this._playlistIndex].stream_url;
}
} else if (this._track) {
src = this._track.stream_url;
}
if (!src) {
throw new Error('There is no tracks to play, use `streamUrl` option or `load` method');
}
if (this._clientId) {
src = _appendQueryParam(src, 'client_id', this._clientId);
}
if (src !== this.audio.src) {
pulse.loadBufferFromURI(src, (event, pulse) => {
this.trackBPM = pulse.beat.bpm
this.audio.src = window.URL.createObjectURL(pulse.renderedBuffer);
this.playing = src;
console.log('trackBPM',pulse.beat.bpm);
})
} else return this.audio.play();
};
Now
pulse.loadBufferFromURI(src, (event, pulse) => {
this.trackBPM = pulse.beat.bpm
this.audio.src = window.URL.createObjectURL(pulse.renderedBuffer);
this.playing = src;
console.log('trackBPM',pulse.beat.bpm);
})
attempts to load the stream_url as aduiobuffer to get the bpm. The question is can I covert the buffer into a source compatible enough to play using <audio> element, reason being I want to take advantage of the event listeners...

MediaRecorder not saving properly in Electron

I am trying to record my screen using media Recorder API using electron like this. I have a start function which starts recording the screen. I use the electron API for this. and a stop function to stop recording using MediaRecorder API from - https://developer.mozilla.org/en-US/docs/Web/API/MediaRecorder.
Currently it stops after 7 seconds.
This is how it looks like.
var electron = require('electron');
var SECRET_KEY = 'test.html';
var recorder;
var blobs = [];
console.log("its loading");
function startRecording() {
var title = document.title;
document.title = SECRET_KEY;
console.log("Started Recording");
electron.desktopCapturer.getSources({ types: ['window', 'screen'] }, function(error, sources) {
if (error) throw error;
for (let i = 0; i < sources.length; i++) {
let src = sources[i];
if (src.name === SECRET_KEY) {
console.log("its passing");
document.title = title;
navigator.webkitGetUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
chromeMediaSourceId: src.id,
minWidth: 800,
maxWidth: 1280,
minHeight: 600,
maxHeight: 720
}
}
}, handleStream, handleUserMediaError);
return;
}
}
});
}
function handleStream(stream) {
recorder = new MediaRecorder(stream);
blobs = [];
recorder.ondataavailable = function(event) {
blobs.push(event.data);
};
recorder.start();
}
function stopRecording() {
recorder.stop();
toArrayBuffer(new Blob(blobs, { type: "video/webm" }), function(ab) {
var buffer = toBuffer(ab);
var file = `./SavedVideos/example.webm`;
fs.writeFile(file, buffer, function(err) {
if (err) {
console.error('Failed to save video ' + err);
} else {
console.log('Saved video: ' + file);
}
});
});
}
function handleUserMediaError(e) {
console.error('handleUserMediaError', e);
}
function toArrayBuffer(blob, cb) {
let fileReader = new FileReader();
fileReader.onload = function() {
let arrayBuffer = this.result;
cb(arrayBuffer);
};
fileReader.readAsArrayBuffer(blob);
}
function toBuffer(ab) {
let buffer = new Buffer(ab.byteLength);
let arr = new Uint8Array(ab);
for (let i = 0; i < arr.byteLength; i++) {
buffer[i] = arr[i];
}
return buffer;
}
var startbutton = document.getElementById('start');
var stopbutton = document.getElementById('stop');
// startbutton.onclick = startRecording();
// stopbutton.onclick = stopRecording();
// Record for 7 seconds and save to disk
startRecording();
setTimeout(function() { stopRecording() }, 7000);
The code is passing without any error. But when I open the video which is saved using VLC, it has 0 bytes and it doesn't start.
How can fix this ?

You didn't wait for value to come in stopReocoring. You need to change your stopRecording function to following:
function stopRecording() {
var save = function() {
console.log(blobs);
toArrayBuffer(new Blob(blobs, {type: 'video/webm'}), function(ab) {
console.log(ab);
var buffer = toBuffer(ab);
var file = `./videos/example.webm`;
fs.writeFile(file, buffer, function(err) {
if (err) {
console.error('Failed to save video ' + err);
} else {
console.log('Saved video: ' + file);
}
});
});
};
recorder.onstop = save;
recorder.stop();
}

Possible memory leak or something else?

I've made a visualizer in javascript that when you select a music directory your're able to select files within that directory to play and have the visualizer move to. But it would seem after loading a directory and then changing the song more than 4 times Results in less responsive movement from the visualizer. I'm unsure why this is happening.
Heres an example of this happening.
Keep changing the song from the drop down box until you see it starting to slow.
window.onload = function() {
var input = document.getElementById("file");
var audio = document.getElementById("audio");
var selectLabel = document.querySelector("label[for=select]");
var audioLabel = document.querySelector("label[for=audio]");
var select = document.querySelector("select");
var context = void 0,
src = void 0,
res = [],
url = "";
function processDirectoryUpload(event) {
var webkitResult = [];
var mozResult = [];
var files;
console.log(event);
select.innerHTML = "";
// do mozilla stuff
function mozReadDirectories(entries, path) {
console.log("dir", entries, path);
return [].reduce.call(entries, function(promise, entry) {
return promise.then(function() {
return Promise.resolve(entry.getFilesAndDirectories() || entry)
.then(function(dir) {
return dir
})
})
}, Promise.resolve())
.then(function(items) {
var dir = items.filter(function(folder) {
return folder instanceof Directory
});
var files = items.filter(function(file) {
return file instanceof File
});
if (files.length) {
// console.log("files:", files, path);
mozResult = mozResult.concat.apply(mozResult, files);
}
if (dir.length) {
// console.log(dir, dir[0] instanceof Directory);
return mozReadDirectories(dir, dir[0].path || path);
} else {
if (!dir.length) {
return Promise.resolve(mozResult).then(function(complete) {
return complete
})
}
}
})
};
function handleEntries(entry) {
let file = "webkitGetAsEntry" in entry ? entry.webkitGetAsEntry() : entry
return Promise.resolve(file);
}
function handleFile(entry) {
return new Promise(function(resolve) {
if (entry.isFile) {
entry.file(function(file) {
listFile(file, entry.fullPath).then(resolve)
})
} else if (entry.isDirectory) {
var reader = entry.createReader();
reader.readEntries(webkitReadDirectories.bind(null, entry, handleFile, resolve))
} else {
var entries = [entry];
return entries.reduce(function(promise, file) {
return promise.then(function() {
return listDirectory(file)
})
}, Promise.resolve())
.then(function() {
return Promise.all(entries.map(function(file) {
return listFile(file)
})).then(resolve)
})
}
})
function webkitReadDirectories(entry, callback, resolve, entries) {
console.log(entries);
return listDirectory(entry).then(function(currentDirectory) {
console.log(`iterating ${currentDirectory.name} directory`, entry);
return entries.reduce(function(promise, directory) {
return promise.then(function() {
return callback(directory)
});
}, Promise.resolve())
}).then(resolve);
}
}
function listDirectory(entry) {
console.log(entry);
return Promise.resolve(entry);
}
function listFile(file, path) {
path = path || file.webkitRelativePath || "/" + file.name;
console.log(`reading ${file.name}, size: ${file.size}, path:${path}`);
webkitResult.push(file);
return Promise.resolve(webkitResult)
};
function processFiles(files) {
Promise.all([].map.call(files, function(file, index) {
return handleEntries(file, index).then(handleFile)
}))
.then(function() {
console.log("complete", webkitResult);
res = webkitResult;
res.reduce(function(promise, track) {
return promise.then(function() {
return playMusic(track)
})
}, displayFiles(res))
})
.catch(function(err) {
alert(err.message);
})
}
if ("getFilesAndDirectories" in event.target) {
return (event.type === "drop" ? event.dataTransfer : event.target).getFilesAndDirectories()
.then(function(dir) {
if (dir[0] instanceof Directory) {
console.log(dir)
return mozReadDirectories(dir, dir[0].path || path)
.then(function(complete) {
console.log("complete:", webkitResult);
event.target.value = null;
});
} else {
if (dir[0] instanceof File && dir[0].size > 0) {
return Promise.resolve(dir)
.then(function() {
console.log("complete:", mozResult);
res = mozResult;
res.reduce(function(promise, track) {
return promise.then(function() {
return playMusic(track)
})
}, displayFiles(res))
})
} else {
if (dir[0].size == 0) {
throw new Error("could not process '" + dir[0].name + "' directory" + " at drop event at firefox, upload folders at 'Choose folder...' input");
}
}
}
}).catch(function(err) {
alert(err)
})
}
files = event.target.files;
if (files) {
processFiles(files)
}
}
function displayFiles(files) {
select.innerHTML = "";
return Promise.all(files.map(function(file, index) {
return new Promise(function(resolve) {
if (/^audio/.test(file.type)) { /* do stuff, that is all code currently within Promise resolver function */ } else { /* proceed to next file */
resolve()
}
var option = new Option(file.name, index);
select.appendChild(option);
resolve()
})
}))
}
function handleSelectedSong(event) {
if (res.length) {
var index = select.value;
var track = res[index];
playMusic(track)
.then(function(filename) {
console.log(filename + " playback completed")
})
} else {
console.log("No songs to play")
}
}
function playMusic(file) {
return new Promise(function(resolve) {
audio.pause();
audio.onended = function() {
audio.onended = null;
if (url) URL.revokeObjectURL(url);
resolve(file.name);
}
if (url) URL.revokeObjectURL(url);
url = URL.createObjectURL(file);
audio.load();
audio.src = url;
audio.play();
audioLabel.textContent = file.name;
context = context || new AudioContext();
src = src || context.createMediaElementSource(audio);
src.disconnect(context);
var analyser = context.createAnalyser();
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var ctx = canvas.getContext("2d");
src.connect(analyser);
analyser.connect(context.destination);
analyser.fftSize = 16384;
var bufferLength = analyser.frequencyBinCount;
console.log(bufferLength);
var dataArray = new Uint8Array(bufferLength);
var WIDTH = canvas.width;
var HEIGHT = canvas.height;
var barWidth = (WIDTH / bufferLength) * 32;
var barHeight;
var x = 0;
function renderFrame() {
requestAnimationFrame(renderFrame);
x = 0;
analyser.getByteFrequencyData(dataArray);
ctx.fillStyle = "#1b1b1b";
ctx.fillRect(0, 0, WIDTH, HEIGHT);
for (var i = 0; i < bufferLength; i++) {
barHeight = dataArray[i];
ctx.fillStyle = "rgb(5,155,45)"
ctx.fillRect(x, (((HEIGHT - barHeight - 5 % barHeight) + (20 % HEIGHT - barHeight))), barWidth, barHeight + 20 % HEIGHT);
x += barWidth + 2;
}
}
renderFrame();
})
}
input.addEventListener("change", processDirectoryUpload);
select.addEventListener("change", handleSelectedSong);
}
<canvas id="canvas" width="window.innerWidth" height="window.innerHeight"></canvas>
<div id="content">
<label class="custom-file-upload">
Select Music directory <input id="file" type="file" accept="audio/*" directory allowdirs webkitdirectory/>
<p style="color: rgb(5,195,5);">Now playing:<label for="audio"></label></p>
<p style="color: rgb(5,195,5);">Select Song</p>
<select id="select">
</select>
<audio id="audio" controls></audio>

Like noted by yuriy636, you are starting a new animation for every new song, without never stopping the previous one.
So when you played 5 songs, you still have 5 visualizations rendering loop running at every frame, and 5 analyzers.
The best to do here is to refactor your code :
create a single analyzer, only update which stream feeds it
make the canvas animation autonomous, declare it once at first load
since you've got only one <canvas>, start only one rendering animation
When using a single analyzer, your render doesn't use anything new when you change the source, it's always the same canvas, the same analyzer, the same visualization.
Here is a quick proof of concept, really dirty, but I hope you'll be able to undertstand what I did and why.
window.onload = function() {
var input = document.getElementById("file");
var audio = document.getElementById("audio");
var selectLabel = document.querySelector("label[for=select]");
var audioLabel = document.querySelector("label[for=audio]");
var select = document.querySelector("select");
var viz = null;
// removed all the IDK what it was meant for directory special handlers
function displayFiles() {
select.innerHTML = "";
// that's all synchronous, why Promises ?
res = Array.prototype.slice.call(input.files);
res.forEach(function(file, index) {
if (/^audio/.test(file.type)) {
var option = new Option(file.name, index);
select.appendChild(option);
}
});
if (res.length) {
var analyser = initAudioAnalyser();
viz = initVisualization(analyser);
// pre-select the first song ?
handleSelectedSong();
audio.pause();
}
}
function handleSelectedSong(event) {
if (res.length) {
var index = select.value;
var track = res[index];
playMusic(track)
.then(function(filename) {
console.log(filename + " playback completed")
})
viz.play();
} else {
console.log("No songs to play")
}
}
function playMusic(file) {
return new Promise(function(resolve) {
var url = audio.src;
audio.pause();
audio.onended = function() {
audio.onended = null;
// arguablily useless here since blobURIs are just pointers to real file on the user's system
if (url) URL.revokeObjectURL(url);
resolve(file.name);
}
if (url) URL.revokeObjectURL(url);
url = URL.createObjectURL(file);
// audio.load(); // would just set a 404 since you revoked the URL just before
audio.src = url;
audio.play();
audioLabel.textContent = file.name;
});
}
function initAudioAnalyser() {
var context = new AudioContext();
var analyser = context.createAnalyser();
analyser.fftSize = 16384;
var src = context.createMediaElementSource(audio);
src.connect(analyser);
src.connect(context.destination);
return analyser;
}
function initVisualization(analyser) {
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var ctx = canvas.getContext("2d");
var bufferLength = analyser.frequencyBinCount;
var dataArray = new Uint8Array(bufferLength);
var WIDTH = canvas.width;
var HEIGHT = canvas.height;
var barWidth = (WIDTH / bufferLength) * 32;
var barHeight;
var x = 0;
var paused = true;
function renderFrame() {
if (!paused) {
requestAnimationFrame(renderFrame);
} else {
return;
}
x = 0;
analyser.getByteFrequencyData(dataArray);
ctx.fillStyle = "#1b1b1b";
ctx.fillRect(0, 0, WIDTH, HEIGHT);
ctx.fillStyle = "rgb(5,155,45)"
ctx.beginPath();
for (var i = 0; i < bufferLength; i++) {
barHeight = dataArray[i];
// micro-optimisation, but concatenating all the rects in a single shape is easier for the CPU
ctx.rect(x, (((HEIGHT - barHeight - 5 % barHeight) + (20 % HEIGHT - barHeight))), barWidth, barHeight + 20 % HEIGHT);
x += barWidth + 2;
}
ctx.fill();
}
var viz = window.viz = {
play: function() {
if(paused){
paused = false;
renderFrame();
}
},
pause: function() {
paused = true;
clearTimeout(pauseTimeout);
pauseTimeout = null;
},
};
// we can even add auto pause linked to the audio element
var pauseTimeout = null;
audio.onpause = function() {
// let's really do it in 2s to keep the tear down effect
pauseTimeout = setTimeout(viz.pause, 2000);
}
audio.onplaying = function() {
clearTimeout(pauseTimeout);
// we were not playing
if(!pauseTimeout){
viz.play();
}
}
return viz;
}
input.addEventListener("change", displayFiles);
select.addEventListener("change", handleSelectedSong);
}
<canvas id="canvas" width="window.innerWidth" height="window.innerHeight"></canvas>
<div id="content">
<label class="custom-file-upload">
Select Music directory <input id="file" type="file" accept="audio/*" directory allowdirs webkitdirectory/>
<p style="color: rgb(5,195,5);">Now playing:<label for="audio"></label></p>
<p style="color: rgb(5,195,5);">Select Song</p>
<select id="select">
</select>
<audio id="audio" controls></audio>

Send base64/byte array of Gif Animation from server side and display it on canvas in client side

I built an interface that calls a web API in asp.net (i use c# and javascript/ajax to implement that).
The client side call to the controller, the controller needs to create animation gif and send it back to the client side by a string of base64 or byte array, when the client side gets the base64 he should display it into a canvas.
Now the problem is that the canvas display only the first frame of the animation gif like a static image.
I already read a lot on the internet and find this:
How Do I Convert A GIF Animation To Base64 String And Back To A GIF Animation?
But it's not helped me because I don't want to save the image on the disc just to display it on the client side.
*Note that when I save the image from server side on my disc its save it as gif and display all frames together like I wish, something wrong when I transfer it to client side.
*I use ImageMagick to create the animated gif.
Here is my client side code:
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="utf-8" />
<link href="Content/bootstrap.min.css" rel="stylesheet" />
</head>
<body style="padding-top: 20px;">
<div class="col-md-10 col-md-offset-1">
<div class="well">
<!---->
<canvas id="canvasImage" width="564" height="120">
<p>We apologize, your browser does not support canvas at this time!</p>
</canvas>
<!---->
</div>
</div>
<script src="Scripts/jquery-1.10.2.min.js"></script>
<script src="Scripts/bootstrap.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {
$.ajax({
url: '/api/EngineProccess',
method: 'GET',
success: function (data) {
var imageObj = new Image();
var canvas = document.getElementById("canvasImage");
var context = canvas.getContext('2d');
var image = new Image();
image.onload = function () {
context.drawImage(image, 0, 0);
};
console.log(data);
image.src = "data:image/gif;base64," + data;
},
error: function (jqXHR) {
$('#divErrorText').text(jqXHR.responseText);
$('#divError').show('fade');
}
});
});
</script>
</body>
</html>
and here is the server code:
public class EngineProccessController : ApiController
{
// GET api/EngineProccess
public String Get()
{
using (MagickImageCollection collection = new MagickImageCollection())
{
// Add first image and set the animation delay to 100ms
collection.Add("Snakeware1.gif");
collection[0].AnimationDelay = 100;
// Add second image, set the animation delay to 100ms and flip the image
collection.Add("Snakeware2.gif");
collection[1].AnimationDelay = 100;
collection[1].Flip();
// Optionally reduce colors
QuantizeSettings settings = new QuantizeSettings();
settings.Colors = 256;
collection.Quantize(settings);
// Optionally optimize the images (images should have the same size).
collection.Optimize();
// Save gif
//collection.Write("D://Test01//Test01//Animated.gif");
string data = collection.ToBase64();
return data;
}
}
}
Any ideas?
Please help.
Edit: after some days i found the problem, i use magicimage (magic.net) to create the gif animaited, the base64 was ok but the problem was in the canvas element, the canvas didnt display the animation likei want so i changed the element canvas to be an regular image element () and the changed the src of the image dynamic.
Regards,
Jr.Rafa

Example loading playing gif on canvas.
Sorry but just under 30K answer limit, code and comment very cut down to fit. Ask in comments if needed. See bottom of snippet on basic usage.
/*
The code was created as to the specifications set out in https://www.w3.org/Graphics/GIF/spec-gif89a.txt
The document states usage conditions
"The Graphics Interchange Format(c) is the Copyright property of
CompuServe Incorporated. GIF(sm) is a Service Mark property of
CompuServe Incorporated."
https://en.wikipedia.org/wiki/GIF#Unisys_and_LZW_patent_enforcement last paragraph
Additional sources
https://en.wikipedia.org/wiki/GIF
https://www.w3.org/Graphics/GIF/spec-gif87.txt
*/
var GIF = function () {
var timerID;
var st;
var interlaceOffsets = [0, 4, 2, 1]; // used in de-interlacing.
var interlaceSteps = [8, 8, 4, 2];
var interlacedBufSize = undefined;
var deinterlaceBuf = undefined;
var pixelBufSize = undefined;
var pixelBuf = undefined;
const GIF_FILE = {
GCExt : 0xF9,
COMMENT : 0xFE,
APPExt : 0xFF,
UNKNOWN : 0x01,
IMAGE : 0x2C,
EOF : 59,
EXT : 0x21,
};
var Stream = function (data) { // simple buffered stream
this.data = new Uint8ClampedArray(data);
this.pos = 0;
var len = this.data.length;
this.getString = function (count) {
var s = "";
while (count--) {
s += String.fromCharCode(this.data[this.pos++]);
}
return s;
};
this.readSubBlocks = function () {
var size, count, data;
data = "";
do {
count = size = this.data[this.pos++];
while (count--) {
data += String.fromCharCode(this.data[this.pos++]);
}
} while (size !== 0 && this.pos < len);
return data;
}
this.readSubBlocksB = function () { // reads a set of blocks as binary
var size, count, data;
data = [];
do {
count = size = this.data[this.pos++];
while (count--) {
data.push(this.data[this.pos++]);
}
} while (size !== 0 && this.pos < len);
return data;
}
};
// LZW decoder uncompressed each frame's pixels
var lzwDecode = function (minSize, data) {
var i, pixelPos, pos, clear, eod, size, done, dic, code, last, d, len;
pos = 0;
pixelPos = 0;
dic = [];
clear = 1 << minSize;
eod = clear + 1;
size = minSize + 1;
done = false;
while (!done) {
last = code;
code = 0;
for (i = 0; i < size; i++) {
if (data[pos >> 3] & (1 << (pos & 7))) {
code |= 1 << i;
}
pos++;
}
if (code === clear) { // clear and reset the dictionary
dic = [];
size = minSize + 1;
for (i = 0; i < clear; i++) {
dic[i] = [i];
}
dic[clear] = [];
dic[eod] = null;
continue;
}
if (code === eod) { // end of data
done = true;
return;
}
if (code >= dic.length) {
dic.push(dic[last].concat(dic[last][0]));
} else
if (last !== clear) {
dic.push(dic[last].concat(dic[code][0]));
}
d = dic[code];
len = d.length;
for (i = 0; i < len; i++) {
pixelBuf[pixelPos++] = d[i];
}
if (dic.length === (1 << size) && size < 12) {
size++;
}
}
};
var parseColourTable = function (count) { // get a colour table of length count
// Each entry is 3 bytes, for RGB.
var colours = [];
for (var i = 0; i < count; i++) {
colours.push([st.data[st.pos++], st.data[st.pos++], st.data[st.pos++]]);
}
return colours;
};
var parse = function () { // read the header. This is the starting point of the decode and async calls parseBlock
var bitField;
st.pos += 6; // skip the first stuff see GifEncoder for details
gif.width = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
gif.height = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
bitField = st.data[st.pos++];
gif.colorRes = (bitField & 0b1110000) >> 4;
gif.globalColourCount = 1 << ((bitField & 0b111) + 1);
gif.bgColourIndex = st.data[st.pos++];
st.pos++; // ignoring pixel aspect ratio. if not 0, aspectRatio = (pixelAspectRatio + 15) / 64
if (bitField & 0b10000000) { // global colour flag
gif.globalColourTable = parseColourTable(gif.globalColourCount);
}
setTimeout(parseBlock, 0);
};
var parseAppExt = function () { // get application specific data. Netscape added iterations and terminator. Ignoring that
st.pos += 1;
if ('NETSCAPE' === st.getString(8)) {
st.pos += 8; // ignoring this data. iterations (word) and terminator (byte)
} else {
st.pos += 3; // 3 bytes of string usually "2.0" when identifier is NETSCAPE
st.readSubBlocks(); // unknown app extension
}
};
var parseGCExt = function () { // get GC data
var bitField;
st.pos++;
bitField = st.data[st.pos++];
gif.disposalMethod = (bitField & 0b11100) >> 2;
gif.transparencyGiven = bitField & 0b1 ? true : false; // ignoring bit two that is marked as userInput???
gif.delayTime = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
gif.transparencyIndex = st.data[st.pos++];
st.pos++;
};
var parseImg = function () { // decodes image data to create the indexed pixel image
var deinterlace, frame, bitField;
deinterlace = function (width) { // de interlace pixel data if needed
var lines, fromLine, pass, toline;
lines = pixelBufSize / width;
fromLine = 0;
if (interlacedBufSize !== pixelBufSize) {
deinterlaceBuf = new Uint8Array(pixelBufSize);
interlacedBufSize = pixelBufSize;
}
for (pass = 0; pass < 4; pass++) {
for (toLine = interlaceOffsets[pass]; toLine < lines; toLine += interlaceSteps[pass]) {
deinterlaceBuf.set(pixelBuf.subArray(fromLine, fromLine + width), toLine * width);
fromLine += width;
}
}
};
frame = {}
gif.frames.push(frame);
frame.disposalMethod = gif.disposalMethod;
frame.time = gif.length;
frame.delay = gif.delayTime * 10;
gif.length += frame.delay;
if (gif.transparencyGiven) {
frame.transparencyIndex = gif.transparencyIndex;
} else {
frame.transparencyIndex = undefined;
}
frame.leftPos = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.topPos = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.width = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
frame.height = (st.data[st.pos++]) + ((st.data[st.pos++]) << 8);
bitField = st.data[st.pos++];
frame.localColourTableFlag = bitField & 0b10000000 ? true : false;
if (frame.localColourTableFlag) {
frame.localColourTable = parseColourTable(1 << ((bitField & 0b111) + 1));
}
if (pixelBufSize !== frame.width * frame.height) { // create a pixel buffer if not yet created or if current frame size is different from previous
pixelBuf = new Uint8Array(frame.width * frame.height);
pixelBufSize = frame.width * frame.height;
}
lzwDecode(st.data[st.pos++], st.readSubBlocksB()); // decode the pixels
if (bitField & 0b1000000) { // de interlace if needed
frame.interlaced = true;
deinterlace(frame.width);
} else {
frame.interlaced = false;
}
processFrame(frame); // convert to canvas image
};
var processFrame = function (frame) {
var ct, cData, dat, pixCount, ind, useT, i, pixel, pDat, col, frame, ti;
frame.image = document.createElement('canvas');
frame.image.width = gif.width;
frame.image.height = gif.height;
frame.image.ctx = frame.image.getContext("2d");
ct = frame.localColourTableFlag ? frame.localColourTable : gif.globalColourTable;
if (gif.lastFrame === null) {
gif.lastFrame = frame;
}
useT = (gif.lastFrame.disposalMethod === 2 || gif.lastFrame.disposalMethod === 3) ? true : false;
if (!useT) {
frame.image.ctx.drawImage(gif.lastFrame.image, 0, 0, gif.width, gif.height);
}
cData = frame.image.ctx.getImageData(frame.leftPos, frame.topPos, frame.width, frame.height);
ti = frame.transparencyIndex;
dat = cData.data;
if (frame.interlaced) {
pDat = deinterlaceBuf;
} else {
pDat = pixelBuf;
}
pixCount = pDat.length;
ind = 0;
for (i = 0; i < pixCount; i++) {
pixel = pDat[i];
col = ct[pixel];
if (ti !== pixel) {
dat[ind++] = col[0];
dat[ind++] = col[1];
dat[ind++] = col[2];
dat[ind++] = 255; // Opaque.
} else
if (useT) {
dat[ind + 3] = 0; // Transparent.
ind += 4;
} else {
ind += 4;
}
}
frame.image.ctx.putImageData(cData, frame.leftPos, frame.topPos);
gif.lastFrame = frame;
if (!gif.waitTillDone && typeof gif.onload === "function") { // if !waitTillDone the call onload now after first frame is loaded
doOnloadEvent();
}
};
var finnished = function () { // called when the load has completed
gif.loading = false;
gif.frameCount = gif.frames.length;
gif.lastFrame = null;
st = undefined;
gif.complete = true;
gif.disposalMethod = undefined;
gif.transparencyGiven = undefined;
gif.delayTime = undefined;
gif.transparencyIndex = undefined;
gif.waitTillDone = undefined;
pixelBuf = undefined; // dereference pixel buffer
deinterlaceBuf = undefined; // dereference interlace buff (may or may not be used);
pixelBufSize = undefined;
deinterlaceBuf = undefined;
gif.currentFrame = 0;
if (gif.frames.length > 0) {
gif.image = gif.frames[0].image;
}
doOnloadEvent();
if (typeof gif.onloadall === "function") {
(gif.onloadall.bind(gif))({
type : 'loadall',
path : [gif]
});
}
if (gif.playOnLoad) {
gif.play();
}
}
var canceled = function () { // called if the load has been cancelled
finnished();
if (typeof gif.cancelCallback === "function") {
(gif.cancelCallback.bind(gif))({
type : 'canceled',
path : [gif]
});
}
}
var parseExt = function () { // parse extended blocks
switch (st.data[st.pos++]) {
case GIF_FILE.GCExt:
parseGCExt();
break;
case GIF_FILE.COMMENT:
gif.comment += st.readSubBlocks(); // found a comment field
break;
case GIF_FILE.APPExt:
parseAppExt();
break;
case GIF_FILE.UNKNOWN: // not keeping this data
st.pos += 13; // deliberate fall through to default
default: // not keeping this if it happens
st.readSubBlocks();
break;
}
}
var parseBlock = function () { // parsing the blocks
if (gif.cancel !== undefined && gif.cancel === true) {
canceled();
return;
}
switch (st.data[st.pos++]) {
case GIF_FILE.IMAGE: // image block
parseImg();
if (gif.firstFrameOnly) {
finnished();
return;
}
break;
case GIF_FILE.EOF: // EOF found so cleanup and exit.
finnished();
return;
case GIF_FILE.EXT: // extend block
default:
parseExt();
break;
}
if (typeof gif.onprogress === "function") {
gif.onprogress({
bytesRead : st.pos,
totalBytes : st.data.length,
frame : gif.frames.length
});
}
setTimeout(parseBlock, 0);
};
var cancelLoad = function (callback) {
if (gif.complete) {
return false;
}
gif.cancelCallback = callback;
gif.cancel = true;
return true;
}
var error = function (type) {
if (typeof gif.onerror === "function") {
(gif.onerror.bind(this))({
type : type,
path : [this]
});
}
gif.onerror = undefined;
gif.onload = undefined;
gif.loading = false;
}
var doOnloadEvent = function () { // fire onload event if set
gif.currentFrame = 0;
gif.lastFrameAt = new Date().valueOf();
gif.nextFrameAt = new Date().valueOf();
if (typeof gif.onload === "function") {
(gif.onload.bind(gif))({
type : 'load',
path : [gif]
});
}
gif.onload = undefined;
gif.onerror = undefined;
}
var dataLoaded = function (data) {
st = new Stream(data);
parse();
}
var loadGif = function (filename) { // starts the load
var ajax = new XMLHttpRequest();
ajax.responseType = "arraybuffer";
ajax.onload = function (e) {
if (e.target.status === 400) {
error("Bad Request response code");
} else if (e.target.status === 404) {
error("File not found");
} else {
dataLoaded(ajax.response);
}
};
ajax.open('GET', filename, true);
ajax.send();
ajax.onerror = function (e) {
error("File error");
};
this.src = filename;
this.loading = true;
}
function play() { // starts play if paused
if (!gif.playing) {
gif.paused = false;
gif.playing = true;
playing();
}
}
function pause() { // stops play
gif.paused = true;
gif.playing = false;
clearTimeout(timerID);
}
function togglePlay(){
if(gif.paused || !gif.playing){
gif.play();
}else{
gif.pause();
}
}
function seekFrame(frame) { // seeks to frame number.
clearTimeout(timerID);
frame = frame < 0 ? (frame % gif.frames.length) + gif.frames.length : frame;
gif.currentFrame = frame % gif.frames.length;
if (gif.playing) {
playing();
} else {
gif.image = gif.frames[gif.currentFrame].image;
}
}
function seek(time) { // time in Seconds
clearTimeout(timerID);
if (time < 0) {
time = 0;
}
time *= 1000; // in ms
time %= gif.length;
var frame = 0;
while (time > gif.frames[frame].time + gif.frames[frame].delay && frame < gif.frames.length) {
frame += 1;
}
gif.currentFrame = frame;
if (gif.playing) {
playing();
} else {
gif.image = gif.frames[gif.currentFrame].image;
}
}
function playing() {
var delay;
var frame;
if (gif.playSpeed === 0) {
gif.pause();
return;
}
if (gif.playSpeed < 0) {
gif.currentFrame -= 1;
if (gif.currentFrame < 0) {
gif.currentFrame = gif.frames.length - 1;
}
frame = gif.currentFrame;
frame -= 1;
if (frame < 0) {
frame = gif.frames.length - 1;
}
delay = -gif.frames[frame].delay * 1 / gif.playSpeed;
} else {
gif.currentFrame += 1;
gif.currentFrame %= gif.frames.length;
delay = gif.frames[gif.currentFrame].delay * 1 / gif.playSpeed;
}
gif.image = gif.frames[gif.currentFrame].image;
timerID = setTimeout(playing, delay);
}
var gif = { // the gif image object
onload : null, // fire on load. Use waitTillDone = true to have load fire at end or false to fire on first frame
onerror : null, // fires on error
onprogress : null, // fires a load progress event
onloadall : null, // event fires when all frames have loaded and gif is ready
paused : false, // true if paused
playing : false, // true if playing
waitTillDone : true, // If true onload will fire when all frames loaded, if false, onload will fire when first frame has loaded
loading : false, // true if still loading
firstFrameOnly : false, // if true only load the first frame
width : null, // width in pixels
height : null, // height in pixels
frames : [], // array of frames
comment : "", // comments if found in file. Note I remember that some gifs have comments per frame if so this will be all comment concatenated
length : 0, // gif length in ms (1/1000 second)
currentFrame : 0, // current frame.
frameCount : 0, // number of frames
playSpeed : 1, // play speed 1 normal, 2 twice 0.5 half, -1 reverse etc...
lastFrame : null, // temp hold last frame loaded so you can display the gif as it loads
image : null, // the current image at the currentFrame
playOnLoad : true, // if true starts playback when loaded
// functions
load : loadGif, // call this to load a file
cancel : cancelLoad, // call to stop loading
play : play, // call to start play
pause : pause, // call to pause
seek : seek, // call to seek to time
seekFrame : seekFrame, // call to seek to frame
togglePlay : togglePlay, // call to toggle play and pause state
};
return gif;
}
/*=================================================================
USEAGE Example below
Image used from Wiki see HTML for requiered image atribution
===================================================================*/
const ctx = canvas.getContext("2d");
ctx.font = "16px arial";
var changeFrame = false;
var changeSpeed = false;
frameNum.addEventListener("mousedown",()=>{changeFrame = true ; changeSpeed = false});
speedInput.addEventListener("mousedown",()=>{changeSpeed = true; changeFrame = false});
const gifSrc = "https://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Odessa_TX_Oil_Well_with_Lufkin_320D_pumping_unit.gif/220px-Odessa_TX_Oil_Well_with_Lufkin_320D_pumping_unit.gif"
var myGif = GIF(); // Creates a new gif
myGif.load(gifSrc); // set URL and load
myGif.onload = function(event){ // fires when loading is complete
frameNum.max = myGif.frameCount-1;
animate();
}
myGif.onprogress = function(event){ // Note this function is not bound to myGif
if(canvas.width !== myGif.width || canvas.height !== myGif.height){
canvas.width = myGif.width;
canvas.height = myGif.height;
ctx.font = "16px arial";
}
if(myGif.lastFrame !== null){
ctx.drawImage(myGif.lastFrame.image,0,0);
}
ctx.fillStyle = "black";
ctx.fillText("Loaded frame "+event.frame,8,20);
frameNum.max = event.frame-1;
frameNum.value = event.frame;
frameText.textContent = frameNum.value + "/" + (frameNum.max-1);
}
myGif.onerror = function(event){
ctx.fillStyle = "black";
ctx.fillText("Could not load the Gif ",8,20);
ctx.fillText("Error : " + event.type,8,40);
}
function animate(){
if(changeFrame){
if(myGif.playing){
myGif.pause();
}
myGif.seekFrame(Number(frameNum.value));
}else if(changeSpeed){
myGif.playSpeed = speedInput.value;
if(myGif.paused){
myGif.play();
}
}
frameNum.value = myGif.currentFrame;
frameText.textContent = frameNum.value + "/" + frameNum.max;
if(myGif.paused){
speedInput.value = 0;
}else{
speedInput.value = myGif.playSpeed;
}
speedText.textContent = speedInput.value;
ctx.drawImage(myGif.image,0,0);
requestAnimationFrame(animate);
}
canvas { border : 2px solid black; }
p { font-family : arial; font-size : 12px }
<canvas id="canvas"></canvas>
<div id="inputs">
<input id="frameNum" type = "range" min="0" max="1" step="1" value="0"></input>
Frame : <span id="frameText"></span><br>
<input id="speedInput" type = "range" min="-3" max="3" step="0.1" value="1"></input>
Speed : <span id="speedText"></span><br>
</div>
<p>Image source <br>By DASL51984 - Original YouTube video by user "derekdz", looped by DASL51984, CC BY-SA 4.0, Link</p>

recorderJS record/download audio buffer WEB AUDIO API

I want to record the audio output from a simple drum sequencer and export it for download as a wav file. I have a live link to my current attempt at this implementation attempt.
The sum output of the sequencer is routed to the variable finalMixNode
yet setting this as the input for the recorder.js doesn't work. I think it may be a problem with the audio context but I can't figure it out. I successfully created a oscillator and recorded its output but I can't extend this to the sequencer.
Here is the main js code in which I am trying to record the output. I'm hoping someone will see what I am missing.
//audio node variables
var context;
var convolver;
var compressor;
var masterGainNode;
var effectLevelNode;
var lowPassFilterNode;
var noteTime;
var startTime;
var lastDrawTime = -1;
var LOOP_LENGTH = 16;
var rhythmIndex = 0;
var timeoutId;
var testBuffer = null;
var currentKit = null;
var reverbImpulseResponse = null;
var tempo = 120;
var TEMPO_MAX = 200;
var TEMPO_MIN = 40;
var TEMPO_STEP = 4;
if (window.hasOwnProperty('AudioContext') && !window.hasOwnProperty('webkitAudioContext')) {
window.webkitAudioContext = AudioContext;
}
$(function() {
init();
toggleSelectedListener();
playPauseListener();
lowPassFilterListener();
reverbListener();
createLowPassFilterSliders();
initializeTempo();
changeTempoListener();
});
function createLowPassFilterSliders() {
$("#freq-slider").slider({
value: 1,
min: 0,
max: 1,
step: 0.01,
disabled: true,
slide: changeFrequency
});
$("#quality-slider").slider({
value: 0,
min: 0,
max: 1,
step: 0.01,
disabled: true,
slide: changeQuality
});
}
function lowPassFilterListener() {
$('#lpf').click(function() {
$(this).toggleClass("active");
$(this).blur();
if ($(this).hasClass("btn-default")) {
$(this).removeClass("btn-default");
$(this).addClass("btn-warning");
lowPassFilterNode.active = true;
$("#freq-slider,#quality-slider").slider( "option", "disabled", false );
}
else {
$(this).addClass("btn-default");
$(this).removeClass("btn-warning");
lowPassFilterNode.active = false;
$("#freq-slider,#quality-slider").slider( "option", "disabled", true );
}
})
}
function reverbListener() {
$("#reverb").click(function() {
$(this).toggleClass("active");
$(this).blur();
if ($(this).hasClass("btn-default")) {
$(this).removeClass("btn-default");
$(this).addClass("btn-warning");
convolver.active = true;
}
else {
$(this).addClass("btn-default");
$(this).removeClass("btn-warning");
convolver.active = false;
}
})
}
function changeFrequency(event, ui) {
var minValue = 40;
var maxValue = context.sampleRate / 2;
var numberOfOctaves = Math.log(maxValue / minValue) / Math.LN2;
var multiplier = Math.pow(2, numberOfOctaves * (ui.value - 1.0));
lowPassFilterNode.frequency.value = maxValue * multiplier;
}
function changeQuality(event, ui) {
//30 is the quality multiplier, for now.
lowPassFilterNode.Q.value = ui.value * 30;
}
function playPauseListener() {
$('#play-pause').click(function() {
var $span = $(this).children("span");
if($span.hasClass('glyphicon-play')) {
$span.removeClass('glyphicon-play');
$span.addClass('glyphicon-pause');
handlePlay();
}
else {
$span.addClass('glyphicon-play');
$span.removeClass('glyphicon-pause');
handleStop();
}
});
}
function toggleSelectedListener() {
$('.pad').click(function() {
$(this).toggleClass("selected");
});
}
function init() {
initializeAudioNodes();
loadKits();
loadImpulseResponses();
}
function initializeAudioNodes() {
context = new webkitAudioContext();
var finalMixNode;
if (context.createDynamicsCompressor) {
// Create a dynamics compressor to sweeten the overall mix.
compressor = context.createDynamicsCompressor();
compressor.connect(context.destination);
finalMixNode = compressor;
} else {
// No compressor available in this implementation.
finalMixNode = context.destination;
}
// Create master volume.
// for now, the master volume is static, but in the future there will be a slider
masterGainNode = context.createGain();
masterGainNode.gain.value = 0.7; // reduce overall volume to avoid clipping
masterGainNode.connect(finalMixNode);
//connect all sounds to masterGainNode to play them
//don't need this for now, no wet dry mix for effects
// // Create effect volume.
// effectLevelNode = context.createGain();
// effectLevelNode.gain.value = 1.0; // effect level slider controls this
// effectLevelNode.connect(masterGainNode);
// Create convolver for effect
convolver = context.createConvolver();
convolver.active = false;
// convolver.connect(effectLevelNode);
//Create Low Pass Filter
lowPassFilterNode = context.createBiquadFilter();
//this is for backwards compatibility, the type used to be an integer
lowPassFilterNode.type = (typeof lowPassFilterNode.type === 'string') ? 'lowpass' : 0; // LOWPASS
//default value is max cutoff, or passing all frequencies
lowPassFilterNode.frequency.value = context.sampleRate / 2;
lowPassFilterNode.connect(masterGainNode);
lowPassFilterNode.active = false;
}
function loadKits() {
//name must be same as path
var kit = new Kit("TR808");
kit.load();
//TODO: figure out how to test if a kit is loaded
currentKit = kit;
}
function loadImpulseResponses() {
reverbImpulseResponse = new ImpulseResponse("sounds/impulse- responses/matrix-reverb2.wav");
reverbImpulseResponse.load();
}
//TODO delete this
function loadTestBuffer() {
var request = new XMLHttpRequest();
var url = "http://www.freesound.org/data/previews/102/102130_1721044-lq.mp3";
request.open("GET", url, true);
request.responseType = "arraybuffer";
request.onload = function() {
context.decodeAudioData(
request.response,
function(buffer) {
testBuffer = buffer;
},
function(buffer) {
console.log("Error decoding drum samples!");
}
);
}
request.send();
}
//TODO delete this
function sequencePads() {
$('.pad.selected').each(function() {
$('.pad').removeClass("selected");
$(this).addClass("selected");
});
}
function playNote(buffer, noteTime) {
var voice = context.createBufferSource();
voice.buffer = buffer;
var currentLastNode = masterGainNode;
if (lowPassFilterNode.active) {
lowPassFilterNode.connect(currentLastNode);
currentLastNode = lowPassFilterNode;
}
if (convolver.active) {
convolver.buffer = reverbImpulseResponse.buffer;
convolver.connect(currentLastNode);
currentLastNode = convolver;
}
voice.connect(currentLastNode);
voice.start(noteTime);
}
function schedule() {
var currentTime = context.currentTime;
// The sequence starts at startTime, so normalize currentTime so that it's 0 at the start of the sequence.
currentTime -= startTime;
while (noteTime < currentTime + 0.200) {
var contextPlayTime = noteTime + startTime;
var $currentPads = $(".column_" + rhythmIndex);
$currentPads.each(function() {
if ($(this).hasClass("selected")) {
var instrumentName = $(this).parents().data("instrument");
switch (instrumentName) {
case "kick":
playNote(currentKit.kickBuffer, contextPlayTime);
break;
case "snare":
playNote(currentKit.snareBuffer, contextPlayTime);
break;
case "hihat":
playNote(currentKit.hihatBuffer, contextPlayTime);
break;
case "tomhi":
playNote(currentKit.tomhiBuffer, contextPlayTime);
break;
case "tommid":
playNote(currentKit.tommidBuffer, contextPlayTime);
break;
case "tomlow":
playNote(currentKit.tomlowBuffer, contextPlayTime);
break;
case "cl":
playNote(currentKit.clBuffer, contextPlayTime);
break;
case "cb":
playNote(currentKit.cbBuffer, contextPlayTime);
break;
case "cp":
playNote(currentKit.cpBuffer, contextPlayTime);
break;
case "cy":
playNote(currentKit.cyBuffer, contextPlayTime);
break;
case "rs":
playNote(currentKit.rsBuffer, contextPlayTime);
break;
}
//play the buffer
//store a data element in the row that tells you what instrument
}
});
if (noteTime != lastDrawTime) {
lastDrawTime = noteTime;
drawPlayhead(rhythmIndex);
}
advanceNote();
}
timeoutId = requestAnimationFrame(schedule)
}
function drawPlayhead(xindex) {
var lastIndex = (xindex + LOOP_LENGTH - 1) % LOOP_LENGTH;
//can change this to class selector to select a column
var $newRows = $('.column_' + xindex);
var $oldRows = $('.column_' + lastIndex);
$newRows.addClass("playing");
$oldRows.removeClass("playing");
}
function advanceNote() {
// Advance time by a 16th note...
// var secondsPerBeat = 60.0 / theBeat.tempo;
//TODO CHANGE TEMPO HERE, convert to float
tempo = Number($("#tempo-input").val());
var secondsPerBeat = 60.0 / tempo;
rhythmIndex++;
if (rhythmIndex == LOOP_LENGTH) {
rhythmIndex = 0;
}
//0.25 because each square is a 16th note
noteTime += 0.25 * secondsPerBeat
// if (rhythmIndex % 2) {
// noteTime += (0.25 + kMaxSwing * theBeat.swingFactor) * secondsPerBeat;
// } else {
// noteTime += (0.25 - kMaxSwing * theBeat.swingFactor) * secondsPerBeat;
// }
}
function handlePlay(event) {
rhythmIndex = 0;
noteTime = 0.0;
startTime = context.currentTime + 0.005;
schedule();
}
function handleStop(event) {
cancelAnimationFrame(timeoutId);
$(".pad").removeClass("playing");
}
function initializeTempo() {
$("#tempo-input").val(tempo);
}
function changeTempoListener() {
$("#increase-tempo").click(function() {
if (tempo < TEMPO_MAX) {
tempo += TEMPO_STEP;
$("#tempo-input").val(tempo);
}
});
$("#decrease-tempo").click(function() {
if (tempo > TEMPO_MIN) {
tempo -= TEMPO_STEP;
$("#tempo-input").val(tempo);
}
});
}
function __log(e, data) {
log.innerHTML += "\n" + e + " " + (data || '');
}
var audio_context;
var recorder;
function startUserMedia() {
var input = finalMixNode;
__log('Media stream created.');
input.start();
__log('Input connected to audio context destination.');
recorder = new Recorder(input);
__log('Recorder initialised.');
}
function startRecording(button) {
recorder && recorder.record();
button.disabled = true;
button.nextElementSibling.disabled = false;
__log('Recording...');
}
function stopRecording(button) {
recorder && recorder.stop();
button.disabled = true;
button.previousElementSibling.disabled = false;
__log('Stopped recording.');
// create WAV download link using audio data blob
createDownloadLink();
recorder.clear();
}
function createDownloadLink() {
recorder && recorder.exportWAV(function(blob) {
var url = URL.createObjectURL(blob);
var li = document.createElement('li');
var au = document.createElement('audio');
var hf = document.createElement('a');
au.controls = true;
au.src = url;
hf.href = url;
hf.download = new Date().toISOString() + '.wav';
hf.innerHTML = hf.download;
li.appendChild(au);
li.appendChild(hf);
recordingslist.appendChild(li);
});
}
window.onload = function init() {
try {
// webkit shim
window.AudioContext = window.AudioContext || window.webkitAudioContext;
navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia;
window.URL = window.URL || window.webkitURL;
// audio_context = new AudioContext;
__log('Audio context set up.');
} catch (e) {
alert('No web audio support in this browser!');
}
startUserMedia();
};

Your finalMixNode is scoped into the initializeAudioNodes() function, therefore it is undefined when you call it from startUserMedia().
Also, this variable is either a dynamicCompressor node or the AudioContext's destination.
Recorderjs needs a node with an output (which AudioDestinationNode doesn't have currently1 ) so make sure to construct your recorder with the final compressor node (or a final gainNode)
Executing this in my js console from your page does work :
var recorder = new Recorder(compressor);
1 Thanks #padenot for noticing me it's being discussed here