The following code

 fn = fullfile (tempdir(), "sombrero.mp4");
 if (! exist (fn, "file"))
   warning ("'%s' doesn't exist, running demo VideoWriter first...", fn);
   demo ("VideoWriter");
 endif
 x = VideoReader (fn);
 im = [];
 while (! isempty (img = readFrame (x)))
   if (isempty (im))
     im = image (img);
     axis off;
   else
     set (im, "cdata", img);
   endif
   drawnow
   pause (1/30);
 endwhile

Produces the following figure

Figure 1

The following code

 r = VideoReader("https://raw.githubusercontent.com/opencv/opencv/master/samples/data/vtest.avi")
 im = [];
 while (r.hasFrame())
   img = readFrame (r);
   if (isempty (im))
     im = image (img);
     axis off;
   else
     set (im, "cdata", img);
   endif
   drawnow
 endwhile

Produces the following output

r =

 class VideoReader:
    Duration [s]    = 79.50
    BitsPerPixel    = 24
    Bitrate         = 818283
    FrameRate [fps] = 10.00
    Height [px]     = 576
    Width [px]      = 768
    Name            = vtest.avi
    Path            = https://raw.githubusercontent.com/opencv/opencv/master/samples/data
    NumberOfFrames  = 795
    FrameNumber     = 0
    VideoFormat     = RGB24
    VideoCodec      = msmpeg4v3
    AspectRatio     = [0 1]

and the following figure

Figure 1