title: How to record video when using face detection api
body: <p>I'm using the android FaceDetector to detect faces. I base on code 
  <a href="https://github.com/googlesamples/android-vision/tree/master/visionSamples/FaceTracker" rel="nofollow">https://github.com/googlesamples/android-vision/tree/master/visionSamples/FaceTracker</a></p>
  
  <p>I want to save the video preview. I have not found a solution , are looking forward to get the best guidance , or a link. Thank all</p>