Videos Stored in D7-s private file system do not play on Android devices
To make it work on android device you need to pass .webm format along with .mp4 of the same video. Please check sample shown below:

&lt;video id="my_vid_id" class="video-js vjs-default-skin" controls preload="auto" width="640" height="264" poster="poster.png" data-setup='{}'&gt;
   &lt;source src="movie.mp4" type='video/mp4' /&gt;
   &lt;source src="movie.webm" type='video/webm' /&gt;
&lt;/video&gt;