Video Embed in FieldFormatter
Instead of #markup, which is filtered, use inline template:

$file_path = 'movie.mp4'

$video = '&lt;video width="480" height="320" controls="controls"&gt;
  &lt;source src="{{ file_path }}"  type="video/mp4"&gt;
&lt;/video&gt;';

$element[$delta] = array(
  '#type' =&gt; 'inline_template',
  '#template' =&gt; $video,
  '#context' =&gt; array(
    'file_path' =&gt; $file_path,
  ),
);