Add graph to display when a user is viewing something per hour of day

Would like to create a graph that displays when a user is viewing something grouped by hour of the day. Also an aggregation between all users may be interesting.

Only thing I'm not sure is to how we will group the views. I have two options

1.
Just add the start viewing time for a certain media stream. So when a user starts watching at 23:30 the movie will be logged in the 23:00-00:00 section of the graph. But the user is maybe still watching the movie after 00:00

2.
I take all play events when a user is started viewing a media stream. For 1 movie I will receive an event every 2 seconds. So when he is still watching it after 00:00 you will see some data in the 00:00 - 01:00 section as well. Ofcourse since there are a LOT of data then, the Y axis will display the percentage instead of the count itself.

Any ideas or suggestions on this would be helpfull :)