Get recorded sound representation in WinJS Application

Question

Hi, there.

I want to create Windows 8 app, using HTML and JavaScript, and want to record sound and represent real time the sound variation with a graphic. I followed this article (http://msdn.microsoft.com/en-us/library/windows/apps/hh452798.aspx) and was able to record the sound to an mp3 file. What I want to achieve, in addition, is to attach to some event, that gives me real time information about the recorder sound. Then using that data I want to analyze it, take all or some of the discrete points of the sound representation, convert them to JSON (for example) and then visualize that information. I have all the available resources unless that I cannot get real time representation. I investigated the "oMediaCapture" object (see code below), but couldn't get such functionality. Then I've tried to use stream and hope that it will propose such functionality. But then I get exception when I try to create "RandomAccessStream", following the MSDN article (http://msdn.microsoft.com/en-us/library/windows/apps/windows.storage.streams.randomaccessstream.aspx). 

var stream = new Windows.Storage.Streams.RandomAccessStream();

Here is my full code:

(function InitSound() {
    var settings = initCaptureSettings();
    initMediaCapture(settings);
})();
 
 
function initCaptureSettings() {
    var captureInitSettings = null;
    captureInitSettings = new Windows.Media.Capture.MediaCaptureInitializationSettings();
    captureInitSettings.audioDeviceId = "";
    captureInitSettings.streamingCaptureMode = Windows.Media.Capture.StreamingCaptureMode.audio;
    captureInitSettings.realTimeModeEnabled = true;
    return captureInitSettings;
}
 
function initMediaCapture(captureInitSettings) {
    oMediaCapture = null;
    oMediaCapture = new Windows.Media.Capture.MediaCapture();
    oMediaCapture.initializeAsync(captureInitSettings).then(function (result) {
        createProfile();
    }, errorHandler);
}
 
function createProfile() {
    profile = Windows.Media.MediaProperties.MediaEncodingProfile.createMp3(Windows.Media.MediaProperties.AudioEncodingQuality.high);
}
 
function errorHandler(e) {
 
}
 
function recordSound() {
    var stream = new Windows.Storage.Streams.RandomAccessStream();
    oMediaCapture.startRecordToStreamAsync(profile, stream).then(function (result) {
            
    }, errorHandler);
    /*Windows.Storage.KnownFolders.videosLibrary.createFileAsync("checkMic.mp3", Windows.Storage.CreationCollisionOption.generateUniqueName).then(function (newFile) {
        storageFile = newFile;
        oMediaCapture.startRecordToStorageFileAsync(profile, storageFile).then(function (result) {
            
        }, errorHandler);
    });*/

So do you see an obvious mistake or just the approach is wrong?

Thank you in advance!

Best regards,

Nikolay Alipiev

Answer 1

You'll need to drop down to C++ and WASAPI to get the raw data to do this analysis. See theWindows Audio Session (WASAPI) sample

--Rob

Answer 2

Hi, Rob.

Thank you for the answer. I thought that WinJS will propose such a functionality, but now I will check the C++ example and will use it. I see that the sample is only in C++. Is this mean that there isn't such a functionality also for C#?

Best regards,

Nikolay Alipiev

Answer 3

Correct. WASAPI (like other low level media handling) is native only.

For some uses you can interop to it from C#, but there is no direct support for this and there are some problems that cannot be avoided with the garbage collector.

--Rob

Answer 4

Rob, thank you very much for the clarification!!!