IPhone : is zooming possible while recording video in avfoundation?

I have been working with avfoundation and trying to zoom the video and record or zooming while recording by following code

    [CaptureSession startRunning];
     NSError *error;
    [VideoDevice lockForConfiguration:&error];
    [VideoDevice setActiveFormat:[VideoDevice.formats objectAtIndex:15]];
    [VideoDevice rampToVideoZoomFactor:5.0 withRate:1.0];
    [VideoDevice unlockForConfiguration];

and when I call

 [MovieFileOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];

it is throwing

[AVCaptureMovieFileOutput startRecordingToOutputFileURL:recordingDelegate:] - no active/enabled connections.'

If I just take a still image then the zoom is working and I can capture still image but I can not only capture video after zooming or zooming while recording.

From this should I infer that still video zooming is not supported by IOS ?

Also I think when I change the video active format which support zoom, it causes the crash, though I am using

[CaptureSession setSessionPreset:AVCaptureSessionPresetHigh];

in my configuration.

Please advice!