I have a simple setup for Desktop Capturing using html5 libraries.
This includes a simple webpage and a chrome-extension. I am using
Extension to get the sourceId
Using the sourceId I call navigator.mediaDevices.getUserMedia to get the MediaStream
This MediaStream is then fed into an instance of MediaRecorder for recording.
This setup works most of the times, but a few times I see that requestData() on MediaRecorder instance returns blob with empty data consistently. I am clueless as to what can cause a running setup to start misbehaving sometimes.
Some weird behaviour that I noticed in the bad state:
When I try to close/refresh the window it doesn't respond.
The MediaStreamTrack object in Step 2) above is 'live' but as soon as I go to Step 3) it becomes 'muted'.
There's no pattern to it, sometimes it even happens when I request for the MediaStreams the very first time(which rules out the possibility that there could be some dangling resources eating up the contexts)
Is there anything that I am doing wrong and am unaware of? Any help/pointers would be highly appreciated!
I currently use Azure Mobile Services with Offline Sync and I it has been working fine. However I now have come to a problem I can't seem to debug. On the PullAsync it never returns, never goes to the Web API, it never errors, it just seems to be stuck somewhere and I don't know where.
IMobileServiceSyncTable<ResponseType> responseTypeTable = MobileService.GetSyncTable<ResponseType>();
await responseTypeTable.PullAsync(responseTypeTable.Where(c => c.CompanyId == companyId));
I use identical code elsewhere with a different type and it works well.
The only thing that happens is the Windows Phone emulator UI locks up, I can press buttons on the keyboard but the input or buttons are all frozen.
I get this on the Debug Output
The thread 0xb80 has exited with code 259 (0x103).
After a 5 seconds and that's about it. Breakpoints everywhere, nothing happening.
The method was in a Command (I'm using MVVMLight). When I call the function on the class initialization and just hold the value it works fine. There is obviously some bug that occurs when calling PullAsync on an event, in an async RelayCommand but getting the call out of there solves the issue.
I'll leave it at that unless anyone comes back with why it is actually happening. This is just a workaround at the moment.
I'm trying to capture audio using WASAPI. My code is largely based on the ChatterBox VoIP sample app. I'm getting audio buffers, but they are all silent (flagged AUDCLNT_BUFFERFLAGS_SILENT).
I'm using Visual Studio Express 2012 for Windows Phone. Running on the emulator.
I had the exact same problem and managed to reproduce it in the ChatterBox sample app if I set Visual Studio to native debugging and at any point stepped through the code.
Also, closing the App without going through the "Stop" procedure and stopping the AudioClient will require you to restart the emulator/device before being able to capture audio data again.
It nearly drove me nuts before I figured out the before mentioned problems but I finally got it working.
So..
1. Be sure to NOT do native debugging
2. Always call IAudioClient->Stop(); before terminating the App.
3. Make sure you pass the correct parameters to IAudioClient->Initialize();
I've included a piece of code that works 100% of the time for me. I've left out error checking for clarity..
LPCWSTR pwstrDefaultCaptureDeviceId =
GetDefaultAudioCaptureId(AudioDeviceRole::Communications);
HRESULT hr = ActivateAudioInterface(pwstrDefaultCaptureDeviceId,
__uuidof(IAudioClient2), (void**)&m_pAudioClient);
hr = m_pAudioClient->GetMixFormat(&m_pwfx);
m_frameSizeInBytes = (m_pwfx->wBitsPerSample / 8) * m_pwfx->nChannels;
hr = m_pAudioClient->Initialize(AUDCLNT_SHAREMODE_SHARED,
AUDCLNT_STREAMFLAGS_NOPERSIST | AUDCLNT_STREAMFLAGS_EVENTCALLBACK,
latency * 10000, 0, m_pwfx, NULL);
hr = m_pAudioClient->SetEventHandle(m_hCaptureEvent);
hr = m_pAudioClient->GetService(__uuidof(IAudioCaptureClient),
(void**)&m_pCaptureClient);
And that's it.. Before calling this code I've started a worker thread that will listen to m_hCaptureEvent and call IAudioCaptureClient->GetBuffer(); whenever the capture event is triggered.
Of course using Microsoft.XNA.Audio.Microphone works fine to, but it's not always an option to reference the XNA framework.. :)
It was a really annoying problem which waste about 2 complete days of mine.My problem was solved by setting AudioClientProperties.eCatagory to AudioCategory_Communications instead of AudioCategory_Other.
After this long try and error period I am not sure that the problem won't repeat in the future because the API doesn't act very stable and every run may return a different result.
Edit:Yeah my guess was true.Restarting the wp emulator makes the buffer silent again.But changing the AudioClientProperties.eCatagory back to AudioCategory_Other again solve it.I still don't know what is wrong with it and what is the final solution.
Again I encounter the same problem and this time commenting (removing) the
properties.eCategory = AudioCategory_Communications;
solve the problem.
I can add my piece of advice for Windows Phone 8.1.
I made the following experiment.
Open capture device. Buffers are not silent.
Open render device with AudioDeviceRole::Communications. Buffers immediately go silent.
Close render device. Buffers are not silent.
Then I opened capture device with AudioDeviceRole::Communications and capture device works fine all the time.
For Windows 10 capture device works all the time, no matter if you open it with AudioDeviceRole::Communications or not.
I've had the same problem. It seems like you can either use only AudioCategory_Other or create an instance of VoipPhoneCall and use only AudioCategory_Communications.
So the solution in my case was to use AudioCategory_Communications and create an outgoing VoipPhoneCall. You should implement the background agents as in Chatterbox VoIP sample app for the VoipCallCoordinator to work .
I'm looking for a way to create a simple HTML table that can be updated in real-time upon a database change event; specifically a new record added.
In other words, think of it like an executive dashboard. If a sale is made and a new line is added in a database (MySQL in my case) then the web page should "refresh" the table with the new line.
I have seen some information on the new using EVENT GATEWAY but all of the examples use Coldfusion as the "pusher" and not the "consumer". I would like to have Coldfusion both update / push an event to the gateway and also consume the response.
If this can be done using a combination of AJAX and CF please let me know!
I'm really just looking to understand where to get started with real-time updating.
Thank you in advance!!
EDIT / Explanation of selected answer:
I ended up going with #bpeterson76's answer because at the moment it was easiest to implement on a small scale. I really like his Datatables suggestion, and that's what I am using to update in close to real time.
As my site gets larger though (hopefully), I'm not sure if this will be a scalable solution as every user will be hitting a "listener" page and then subsequently querying my DB. My query is relatively simple, but I'm still worried about performance in the future.
In my opinion though, as HTML5 starts to become the web standard, the Web Sockets method suggested by #iKnowKungFoo is most likely the best approach. Comet with long polling is also a great idea, but it's a little cumbersome to implement / also seems to have some scaling issues.
So, let's hope web users start to adopt more modern browsers that support HTML5, because Web Sockets is a relatively easy and scalable way to get close to real time.
If you feel that I made the wrong decision please leave a comment.
Finally, here is some source code for it all:
Javascript:
note, this is a very simple implementation. It's only looking to see if the number of records in the current datatable has changed and if so update the table and throw an alert. The production code is much longer and more involved. This is just showing a simple way of getting a close to real-time update.
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.js"></script>
<script type="text/javascript" charset="utf-8">
var originalNumberOfRecsInDatatable = 0;
var oTable;
var setChecker = setInterval(checkIfNewRecordHasBeenAdded,5000); //5 second intervals
function checkIfNewRecordHasBeenAdded() {
//json object to post to CFM page
var postData = {
numberOfRecords: originalNumberOfRecsInDatatable
};
var ajaxResponse = $.ajax({
type: "post",
url: "./tabs/checkIfNewItemIsAvailable.cfm",
contentType: "application/json",
data: JSON.stringify( postData )
})
// When the response comes back, if update is available
//then re-draw the datatable and throw an alert to the user
ajaxResponse.then(
function( apiResponse ){
var obj = jQuery.parseJSON(apiResponse);
if (obj.isUpdateAvail == "Yes")
{
oTable = $('#MY_DATATABLE_ID').dataTable();
oTable.fnDraw(false);
originalNumberOfRecsInDatatable = obj.recordcount;
alert('A new line has been added!');
}
}
);
}
</script>
Coldfusion:
<cfset requestBody = toString( getHttpRequestData().content ) />
<!--- Double-check to make sure it's a JSON value. --->
<cfif isJSON( requestBody )>
<cfset deserializedResult = deserializeJSON( requestBody )>
<cfset numberOFRecords = #deserializedResult.originalNumberOfRecsInDatatable#>
<cfquery name="qCount" datasource="#Application.DBdsn#" username="#Application.DBusername#" password="#Application.DBpw#">
SELECT COUNT(ID) as total
FROM myTable
</cfquery>
<cfif #qCount.total# neq #variables.originalNumberOfRecsInDatatable#>
{"isUpdateAvail": "Yes", "recordcount": <cfoutput>#qCount.total#</cfoutput>}
<cfelse>
{"isUpdateAvail": "No"}
</cfif>
</cfif>
This isn't too difficult. The simple way would be to add via .append:
$( '#table > tbody:last').append('<tr id="id"><td>stuff</td></tr>');
Adding elements real-time isn't entirely possible. You'd have to run an Ajax query that updates in a loop to "catch" the change. So, not totally real-time, but very, very close to it. Your user really wouldn't notice the difference, though your server's load might.
But if you're going to get more involved, I'd suggest looking at DataTables. It gives you quite a few new features, including sorting, paging, filtering, limiting, searching, and ajax loading. From there, you could either add an element via ajax and refresh the table view, or simply append on via its API. I've been using DataTables in my app for some time now and they've been consistently cited as the number 1 feature that makes the immense amount of data usable.
--Edit --
Because it isn't obvious, to update the DataTable you call set your Datatables call to a variable:
var oTable = $('#selector').dataTable();
Then run this to do the update:
oTable.fnDraw(false);
UPDATE -- 5 years later, Feb 2016:
This is much more possible today than it was in 2011. New Javascript frameworks such as Backbone.js can connect directly to the database and trigger changes on UI elements including tables on change, update, or delete of data....it's one of these framework's primary benefits. Additionally, UI's can be fed real-time updates via socket connections to a web service, which can also then be caught and acted upon. While the technique described here still works, there are far more "live" ways of doing things today.
You can use SSE (Server Sent Events) a feature in HTML5.
Server-Sent Events (SSE) is a standard describing how servers can initiate data transmission towards clients once an initial client connection has been established. They are commonly used to send message updates or continuous data streams to a browser client and designed to enhance native, cross-browser streaming through a JavaScript API called EventSource, through which a client requests a particular URL in order to receive an event stream.
heres a simple example
http://www.w3schools.com/html/html5_serversentevents.asp
In MS SQL, you can attach a trigger to a table insert/delete/update event that can fire a stored proc to invoke a web service. If the web service is CF-based, you can, in turn, invoke a messaging service using event gateways. Anything listening to the gateway can be notified to refresh its contents. That said, you'd have to see if MySQL supports triggers and accessing web services via stored procedures. You'd also have to have some sort of component in your web app that's listening to the messaging gateway. It's easy to do in Adobe Flex applications, but I'm not sure if there are comparable components accessible in JavaScript.
While this answer does not come close to directly addressing your question, perhaps it will give you some ideas as to how to solve the problem using db triggers and CF messaging gateways.
M. McConnell
With "current" technologies, I think long polling with Ajax is your only choice. However, if you can use HTML5, you should take a look at WebSockets which gives you the functionality you want.
http://net.tutsplus.com/tutorials/javascript-ajax/start-using-html5-websockets-today/
WebSockets is a technique for two-way communication over one (TCP) socket, a type of PUSH technology. At the moment, it’s still being standardized by the W3C; however, the latest versions of Chrome and Safari have support for WebSockets.
http://html5demos.com/web-socket
Check out AJAX long polling.
Place to start Comet
No, you can't have any db code execute server side code. But you could write a service to poll the db periodically to see if a new record has been added then notify the code you have that needs pseudo real-time updates.
The browser can receive real-time updates via BOSH connection to Jabber/XMPP server. All bits and pieces can be found in this book http://professionalxmpp.com/ which I highly recommend. If you can anyhow send XMPP message upon record addition in your DB, then it is relatively easy to build the dashboard you want. You need strophe.js, Jabber/XMPP server (e.g. ejabberd), http server for proxying http-bind requests. All the details can be found in the book. A must read which I strongly believe will solve your problem.
The way I would achieve the notification is after the database update has been successfully committed I would publish an event that would tell any listening systems or even web pages that the change has occurred. I've detailed one way of doing this using an e-commerce solution in a recent blog post. The blog post shows how to trigger the event in ASP.NET but the same thing can easily be done in any other language since ultimately the trigger is performed via a REST API call.
The solution in this blog post uses Pusher but there's not reason why you couldn't install your own real-time server or use a Message Queue to communication between your app and the realtime server, which would then push the notification to the web page or client application.
We want to create a Windows desktop version of our weather widget
There are 2 special things about the widget.
It consumes a lot of processor time
while active - it displays an
animated picture (Flash without GPU acceleration, unfortunately).
It updates the weather from our
server (frequent server requests from all widget users).
When the user does not look at the widget there is no need for animation and weather loading.
So I have an idea of putting my widget to sleep when it is not visible and hense not used.
Is it possible to detect whether the widget is used or not.
Speaking precisely I need to know whether the widget is covered by other windows?
I mostly interested in Vista/7 gadgets engine, however I also would like to know if this problem is solved in these widget engines
Yahoo widgets
Google desktop
Hope to find some desktop widget guru here.
Pasha
If you InvalidateRect and don't get a subsequent WM_PAINT message, than your window is hidden. You can call UpdateWindow after InvalidateRect to force the WM_PAINT message to happen (or not happen) right away.
So you could do something like this
request server data (and cancel request timer if any)
when data arrives InvalidateRect
when WM_PAINT message arrives, draw the data and set a timer for next request
when timer arrives, goto 1
When you stop getting WM_PAINT messages, you stop re-setting your timer, and you therefor stop requesting updates from the server. When the WM_PAINT message happens (because you are no longer covered). You start requesting data again.