It depends on how your video renders times longer than an hour.
If your video rendering site is something like youtube and renders times longer than one hour as something like 1:05:36 then I would recommend going with the hour:mm:sec approach as users can quickly see the start time and get the particular point by hovering over the video bar as shown in the example given below
However, if it for some reason renders time as 68:34 then you might be better off going the route of showing the total sum of minutes as users will use that as the reference point to define the start point and will scan across the video play bar to determine where to click.
However be careful not to mix the both time options i.e. showing time as 68:43 when your video shows the time in hh:mm:ss format and vice versa as that would put a mental load on your user to translate the times from one format to another.