title: i want to capture square video in iOS with custom control
body: <p>i am able to show square preview of recording using AVCaptureVideoPreviewLayer class, But it saving video in rectangular in library. Instead of rectangle i want square video. I have used composition class to crop video and  it is working but taking too much time. I check vine app which has square video output.</p>
  
  <p>Please give me suggestion.</p>