Capture total time spent by a user in a youtube video

I have a website, www.onlinelearningcenter.in. where i provide some free course and some paid course. Please visit the website and click on grab 55 hours of free course from the homepage, and you will be able to see the courses. All free courses videos are actually uploaded in youtube channel and it is just played through the website. I want to keep the functionality, where any user who watches a particular video from youtube, we should be able to record the total number of hours he is watching the video. Say if the user has just watched the first 10 sec of video and then downloads the video using IDM or any downloader and then skips the video and watches the last 10 sec of video, We should be able to say that the user has just watched 20 seconds of video. We will have to keep updating the seconds on database every say 10 [login to view URL] that if there are any internet connectivity issues, we will lose hardly 10 secs of tracking. Then we will have to create a reporting , where we can see the list of all the users who have watched say 80% of the videos through our website. Intention: We will offer some more course to all the users who has watched the video from our website instead of downloading it and watching it offline. This way we will be improving our youtube average hours and we will have our videos better recommeded. Note: You must first develop a POC to show case that you are able to track the timings correctly. After POC, you should be developing this functionality remotely on my machine. You can use your machine to do all your RnD work. coz this is just a small piece of code, and I am not comfortable sharing the ending sourcecode for a small fix. Please donot Bid for the project if you cannot work remotely. This is really a small requirement. We have more complete solution to built.