code: function (successCallback, errorCallback) {
              try {
                  createCameraUI();
                  startCameraPreview(function () {
                      // This callback called twice: whem video capture started and when it ended
                      // so we need to check capture status
                      if (!captureStarted) {
                          // remove cancel button and rename 'Take' button to 'Stop'
                          toggleElements('cancelCapture');
                          document.getElementById('takePicture').text = 'Stop';
  
                          var encodingProperties = Windows.Media.MediaProperties.MediaEncodingProfile.createMp4(Windows.Media.MediaProperties.VideoEncodingQuality.auto),
                              generateUniqueCollisionOption = Windows.Storage.CreationCollisionOption.generateUniqueName,
                              localFolder = Windows.Storage.ApplicationData.current.localFolder;
  
                          localFolder.createFileAsync("cameraCaptureVideo.mp4", generateUniqueCollisionOption).done(function(capturedFile) {
                              capture.startRecordToStorageFileAsync(encodingProperties, capturedFile).done(function() {
                                  capturedVideoFile = capturedFile;
                                  captureStarted = true;
                              }, function(err) {
                                  destroyCameraPreview();
                                  errorCallback(CaptureError.CAPTURE_INTERNAL_ERR, err);
                              });
                          }, function(err) {
                              destroyCameraPreview();
                              errorCallback(CaptureError.CAPTURE_INTERNAL_ERR, err);
                          });
                      } else {
                          capture.stopRecordAsync().done(function () {
                              destroyCameraPreview();
                              successCallback(capturedVideoFile);
                          });
                      }
                  }, errorCallback);
              } catch (ex) {
                  destroyCameraPreview();
                  errorCallback(CaptureError.CAPTURE_INTERNAL_ERR, ex);
              }
          }
docs: Initiate video capture using MediaCapture class
  @param  {function} successCallback Called, when user clicked on preview, with captured file object
  @param  {function} errorCallback   Called on any error