Detecting faces in video file. Error in using data type

I have the following question. I'm working with matlab 2016. I want to detect faces in a video file, using the Viola-Jones algorithm. When I try to enter a video file in & lt;step> the statement, I get the following error:

Error using
   vision.CascadeObjectDetector/validateInputsImpl
   (line 330)
   Expected input number 2 to be
   one of these types:

     uint8, uint16, double, single,int16

     Instead its type was
     vision.VideoFileReader.

     Error in VJ1_video (line 12)
     bboxes = step(faceDetector, videoFReader);

I understand that somehow the type of VideoFileReader should be converted to one of the types: uint8, uint16, double, single, int16. But I do not understand how this can be done. Tell me please. Here is my program code:

clear all;
%Load the video using a video reader object
  videoFReader = vision.VideoFileReader('D:\465.avi');
%Create a detector object.
  faceDetector = vision.CascadeObjectDetector;
%Detect faces.
  bboxes = step(faceDetector, videoFReader);
%Annotate detected faces
  IFaces = insertObjectAnnotation(videoFReader, 'rectangle', bboxes, 'Лицо');
%Create a video player object to play the video file.
  videoPlayer = vision.VideoPlayer;

%Use a while loop to read and play the video frames.
  while ~isDone(videoFReader)
    videoFrame = videoFReader();
    videoPlayer(videoFrame);
  end
%Release the objects.
  release(videoPlayer);
  release(videoFReader);

Answer 1

[Walter Roberson]

The detect and annotate steps should be inside the frame reading loop. The second argument to the detection step() should be the frame that was read in.

[Peter Saytsev]

It is necessary video file is split into frames, and then as a separate image processing operator step?

[Walter Roberson]

%Load the video using a video reader object
  videoFReader = vision.VideoFileReader('D:\465.avi');
%Create a detector object.
  faceDetector = vision.CascadeObjectDetector;

%Create a video player object to play the video file.
  videoPlayer = vision.VideoPlayer;

%Use a while loop to read and play the video frames.
  while ~isDone(videoFReader)
    videoFrame = step(videoFReader);
    %Detect faces.
    bboxes = step(faceDetector, videoFrame);
    %Annotate detected faces
    IFaces = insertObjectAnnotation(videoFrame, 'rectangle', bboxes, 'Лицо');
    step(videoPlayer, videoFrame);
  end
%Release the objects.
  release(videoPlayer);
  release(videoFReader);

[Peter Saytsev]

Thank you very much