Develop Reference

Silence when Playing AAC Chunks

I'm attempting to use Aurora.JS to play audio received from a streaming AAC-encoded source. I'm successfully pulling chunked data, and trying to feed it into a custom emitter, but no audio is actually playing.
Maybe I'm missing something very simple. Here's a sample of what I'm trying to do:
http://jsfiddle.net/Rc6Su/4/
(You're almost certainly gonna get a CORS error when hitting "Play" because the source is cross-domain. The only way I can easily get around that is using this plugin: https://chrome.google.com/webstore/detail/allow-control-allow-origi/nlfbmbojpeacfghkpbjhddihlkkiljbi/related?hl=en)
Before you mention it, this is going into a PhoneGap app and so the cross-domain issue isn't going to be a problem.
The problem code is somewhere in here:
var aurora_source = null;
var player = null;
function make_noise(chunk) {
var uarr = (function (chunk) {
var buf = new ArrayBuffer(chunk.length * 2); // 2 bytes for each character
var bufView = new Uint8Array(buf);
for (var i=0, strLen=chunk.length; i<strLen; i++) {
bufView[i] = chunk.charCodeAt(i);
}
return buf;
})(chunk);
var abData = new AV.Buffer(uarr);
if (!aurora_source) {
var MySource = AV.EventEmitter.extend ({
start : function () {
this.emit('data', abData);
},
pause : function () {
},
reset : function () {
}
});
aurora_source = new MySource();
asset = new AV.Asset(aurora_source);
player = new AV.Player(asset);
player.play();
} else {
$("#debug").append("emit data");
$("#debug").append("\n");
aurora_source.emit('data', abData);
}
}

Could not get audio to play, but found at least that
bufView[i] = chunk.charCodeAt(i);
may have to be replaced by
bufView[i] = chunk.charCodeAt(i) & 0xff;
see What does charCodeAt(...) & 0xff accomplish?
hope it helps.

Firefox Extension/Addon : Reading a text file from remote server(URL)

After wasting my two days to find out what's going wrong with this script, finally I decide to ask it.
What I am trying to do
I am trying to read a text file from remote server. Then storing all text file updates to an SQLITE database at the time of my Firefox Extension/Addon get loaded.
What I tried
var updatereader = {
start: function () {
//alert('reading update');
var fURL = null;
var ioService = null;
var fURI = null;
var httpChannel = null;
fURL = "http://www.example.com/addon/mlist.txt";
ioService = Components.classes["#mozilla.org/network/io-service;1"].getService(Components.interfaces.nsIIOService);
fURI = ioService.newURI(fURL, null, null);
httpChannel = ioService.newChannelFromURI(fURI).QueryInterface(Components.interfaces.nsIHttpChannel);
httpChannel.asyncOpen(updatereader.StreamReader, null);
},
onUpdateCompleted: function () {
},
StreamReader:
{
fOutputStream: null,
fPointer: null,
tempFile: "mlist.txt",
onStartRequest: function (aRequest, aContext) {
//alert('onStart');
updatereader.StreamReader.fOutputStream = Components.classes["#mozilla.org/network/file-output-stream;1"].createInstance(Components.interfaces.nsIFileOutputStream);
updatereader.StreamReader.fPointer = Components.classes["#mozilla.org/file/directory_service;1"].getService(Components.interfaces.nsIProperties).get("ProfD", Components.interfaces.nsIFile);
updatereader.StreamReader.fPointer.append(updatereader.StreamReader.tempFile);
updatereader.StreamReader.fOutputStream.init(updatereader.StreamReader.fPointer, 0x02 | 0x20 | 0x08, 0644, 0);
},
onDataAvailable: function (aRequest, aContext, aInputStream, aOffset, aCount) {
//control flow is not entering here - may be here is somehting missing
var sStream = null;
var tempBuffer = null;
sStream = Components.classes["#mozilla.org/scriptableinputstream;1"].createInstance(Components.interfaces.nsIScriptableInputStream);
sStream.init(aInputStream);
tempBuffer = sStream.read(aCount);
updatereader.StreamReader.fOutputStream.write(tempBuffer, aCount);
},
onStopRequest: function (aRequest, aContext, aStatusCode) {
//alert('onStop');
var currentDate = new Date();
if (aStatusCode == 0) {
fileInputStream = Components.classes["#mozilla.org/network/file-input-stream;1"].createInstance(Components.interfaces.nsIFileInputStream);
updatereader.StreamReader.fOutputStream.close();
fileInputStream.init(updatereader.StreamReader.fPointer, 0x01, 0, 0);
lineInputStream = fileInputStream.QueryInterface(Components.interfaces.nsILineInputStream);
//pass data to somewhere
var dbH = new dbstore();
dbH.updateData(lineInputStream);
lineInputStream.close();
updatereader.StreamReader.fPointer.remove(false);
updatereader.onUpdateCompleted();
} else {
}
}
}
}
Problem:
Getting nothing in lineInputStream which passes the read data to somewhere else for storing it.
Area of problem:
Program control flow is not entring to this section
onDataAvailable:
Not getting any error.

First of all, there doesn't really seem to be any need to read the file to the disk first (unless it is really, really big).
I'd just use XMLHttpRequest to get the file, which when run from a privileged context (e.g. add-on code, but not a website) can access any and every valid URI.
XMLHttpRequest will simplify almost everything, e.g. no more onDataAvailable, (usually) no more manual text converting, etc.
Also, no need to ever hit the disk during the transfer.
Code would look something like this:
var req = new XMLHttpRequest();
req.open("GET", "http://www.example.com/addon/mlist.txt"); // file:/// would work too, BTW
req.overrideMimeType("text/plain");
req.addEventListener("load", function() {
// Do something with req.responseText
}, false);
req.addEventListener("error", function() {
// Handle error
}, false);
req.send();
If you want to use XMLHttpRequest in a non-window, e.g. js code module or js components, then you need to first initialize a constructor. This is not required for windows, including XUL windows and by that XUL overlays.
// Add XMLHttpRequest constructor, if not already present
if (!('XMLHttpRequest' in this)) {
this.XMLHttpRequest = Components.Constructor("#mozilla.org/xmlextras/xmlhttprequest;1", "nsIXMLHttpRequest");
}
SDK users should use the request module, or net/xhr if a lower-level API is required.
PS: If you're still interested in using raw channels, here is a minimal example I coded up in a Scratchpad (to run, open a Scratchpad for a privileged location, e.g. about:newtab).
You shouldn't alert from your own implementation: alert() will spin the event loop and causes reentrant code, which is not supported in this context.
var {
classes: Cc,
interfaces: Ci,
results: Cr,
utils: Cu
} = Components;
Cu.import("resource://gre/modules/XPCOMUtils.jsm")
Cu.import("resource://gre/modules/Services.jsm");
var ConverterStream = Components.Constructor(
"#mozilla.org/intl/converter-input-stream;1",
"nsIConverterInputStream",
"init");
var RC = Ci.nsIConverterInputStream.DEFAULT_REPLACEMENT_CHARACTER;
function Listener() {
this.content = "";
}
Listener.prototype = {
QueryInterface: XPCOMUtils.generateQI([Ci.nsIStreamListener]),
onStartRequest: function(req, ctx) {
console.log("start");
},
onDataAvailable: function(req, ctx, stream, offset, count) {
console.log("data", count);
try {
var cs = new ConverterStream(stream, null /* utf-8 */, 4096, RC);
try {
var str = {};
while (cs.readString(4096, str)) {
this.content += str.value;
}
}
finally {
cs.close();
}
}
catch (ex) {
console.error("data", ex.message, ex);
}
},
onStopRequest: function(req, ctx, status) {
console.log("stop", status,
this.content.substr(0, 20), this.content.length);
}
};
var uri = Services.io.newURI("http://example.org", null, null);
Services.io.newChannelFromURI(uri).asyncOpen(new Listener(), null);

Capture microphone in IE10

I need to capture microphone audio in IE10. So far I have two semi-working solutions:
getUserMedia from Microsoft's experimental WebRTC plugin:
http://www.html5labs.com/prototypes/media-capture-api-(2nd-updated)/media-capture-api-(2nd-update)/info
The issue with this is that while I can capture and replay the audio in the browser, I cannot send the audio to the server. In particular, it is not clear how to extract the audio data from the "blob" object:
function msStopRecordCallback(blob) {
console.log(blob) // outputs {}
console.dir(blob) // outputs {}
playMediaObject.Play(blob); // This works!
}
jRecorder: http://www.sajithmr.me/jrecorder-jquery The issue with this is that it relies on Flash to capture the audio, which is something I would like to avoid.
Are there any other ways to capture audio in IE10?

I recognize that my answer a bit late, but...
You may upload a blob to a server as following (Javascript):
function saveBlob(blob)
{
var uploader = new CustomXMLHttpRequest();
uploader.onpartreceived = function (response)
{
// TODO: handle the server response here
};
var base = window.location.toString();
var uploadService = base.substr(0, base.lastIndexOf("/")) + "/api/upload";
uploader.open("POST", uploadService, true);
uploader.responseType = "text";
var form = new FormData();
form.append("fname", blob, "audio.wav");
uploader.send(form);
}
On the server side, you may treat this blob as a file attachment, e.g. (C#):
public class UploadController : ApiController
{
public async Task<HttpResponseMessage> PostFile()
{
// Check if the request contains multipart/form-data.
if (!Request.Content.IsMimeMultipartContent())
{
throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}
var root = HttpContext.Current.Server.MapPath("~/App_Data");
var provider = new MultipartFormDataStreamProvider(root);
try
{
// Read the form data and return an async task.
await Request.Content.ReadAsMultipartAsync(provider);
var fileName = "";
// get the uploaded files.
foreach (var data in provider.FileData)
{
var file = new FileInfo(data.LocalFileName);
// TODO: handle received file here
}
if (string.IsNullOrEmpty(fileName))
{
return Request.CreateResponse(HttpStatusCode.UnsupportedMediaType);
}
return Request.CreateResponse(HttpStatusCode.OK);
}
catch (System.Exception e)
{
return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);
}
}
}
Hope this will help.

How to change emscripten browser input method from window.prompt to something more sensible?

I have a C++ function which once called consumes input from stdin. Exporting this function to javascript using emscripten causes calls to window.prompt.
Interacting with browser prompt is really tedious task. First of all you can paste only one line at time. Secondly the only way to indicate EOF is by pressing 'cancel'. Last but not least the only way (in case of my function) to make it stop asking user for input by window.prompt is by checking the checkbox preventing more prompts to pop up.
For me the best input method would be reading some blob. I know I can hack library.js but I see some problems:
Reading blob is asynchronous.
To read a blob, first you have to open a file user has to select first.
I don't really know how to prevent my function from reading this blob forever - there is no checkbox like with window.prompt and I'm not sure if spotting EOF will stop it if it didn't in window.prompt case (only checking a checkbox helped).
The best solution would be some kind of callback but I would like to see sime hints from more experienced users.

A way would be to use the Emscripten Filesystem API, for example by calling FS.init in the Module preRun function, passing a custom function as the standard input.
var Module = {
preRun: function() {
function stdin() {
// Return ASCII code of character, or null if no input
}
var stdout = null; // Keep as default
var stderr = null; // Keep as default
FS.init(stdin, stdout, stderr);
}
};
The function is quite low-level: is must deal with one character at a time. To read some data from a blob, you could do something like:
var data = new Int8Array([1,2,3,4,5]);
var blob = new Blob([array], {type: 'application/octet-binary'});
var reader = new FileReader();
var result;
reader.addEventListener("loadend", function() {
result = new Int8Array(reader.result);
});
var i = 0;
var Module = {
preRun: function() {
function stdin() {
if (if < result.byteLength {
var code = result[i];
++i;
return code;
} else {
return null;
}
}
var stdout = null; // Keep as default
var stderr = null; // Keep as default
FS.init(stdin, stdout, stderr);
}
};
Note (as you have hinted), due to the asynchronous nature of the reader, there could be a race condition: the reader must have loaded before you can expect the data at the standard input. You might need to implement some mechanism to avoid this in a real case. Depending on your exact requirements, you could make it so the Emscripten program doesn't actually call main() until you have the data:
var fileRead = false;
var initialised = false;
var result;
var array = new Int8Array([1,2,3,4,5]);
var blob = new Blob([array], {type: 'application/octet-binary'});
var reader = new FileReader();
reader.addEventListener("loadend", function() {
result = new Int8Array(reader.result);
fileRead = true;
runIfCan();
});
reader.readAsArrayBuffer(blob);
var i = 0;
var Module = {
preRun: function() {
function stdin() {
if (i < result.byteLength)
{
var code = result[i];
++i;
return code;
} else{
return null;
}
}
var stdout = null;
var stderr = null;
FS.init(stdin, stdout, stderr);
initialised = true;
runIfCan();
},
noInitialRun: true
};
function runIfCan() {
if (fileRead && initialised) {
// Module.run() doesn't seem to work here
Module.callMain();
}
}
Note: this is a version of my answer at Providing stdin to an emscripten HTML program? , but with focus on the standard input, and adding parts about passing data from a Blob.

From what I understand you could try the following:
Implement selecting a file in Javascript and access it via Javascript Blob interface.
Allocate some memory in Emscripten
var buf = Module._malloc( blob.size );
Write the content of your Blob into the returned memory location from Javascript.
Module.HEAPU8.set( new Uint8Array(blob), buf );
Pass that memory location to a second Emscripten compiled function, which then processes the file content and
Deallocate allocated memory.
Module._free( buf );
Best to read the wiki first.

Javascript String nodejs stream implementation

I need a nodejs stream (http://nodejs.org/api/stream.html) implementation that sends data to a string. Do you know anyone?
To be direct I'm trying to pipe a request response like this:
request('http://google.com/doodle.png').pipe(fs.createWriteStream('doodle.png'))
FROM https://github.com/mikeal/request
Thanks

It would not be difficult to write a class that conforms to the Stream interface; here's an example that implements the very basics, and seems to work with the request module you linked:
var stream = require('stream');
var util = require('util');
var request = require('request');
function StringStream() {
stream.Stream.call(this);
this.writable = true;
this.buffer = "";
};
util.inherits(StringStream, stream.Stream);
StringStream.prototype.write = function(data) {
if (data && data.length)
this.buffer += data.toString();
};
StringStream.prototype.end = function(data) {
this.write(data);
this.emit('end');
};
StringStream.prototype.toString = function() {
return this.buffer;
};
var s = new StringStream();
s.on('end', function() {
console.log(this.toString());
});
request('http://google.com').pipe(s);

You might find the class Sink in the pipette module to be handy for this use case. Using that you can write:
var sink = new pipette.Sink(request(...));
sink.on('data', function(buffer) {
console.log(buffer.toString());
}
Sink also handles error events coming back from the stream reasonably gracefully. See https://github.com/Obvious/pipette#sink for details.
[Edit: because I realized I used the wrong event name.]