video files are very heavy i.e. of large size, will them self take time to load, better use gif file, instead.

A gif that has the same animation as a video will be MUCH larger. Also, there are no "commands" in HTML, I believe you mean Javascript. So, depending on which video player you use you should be able to get the amount played and the length of the video. You would want to set the window location to something after the amount played is equal to the video length.