total dur_gen (Total Duration of Videos - web button)

Hello. I'm building a website where i need to calculate the total duration of user selected video files without uploading the entire lot of videos to my server. Basically I'd like a button that allows the user to choose multiple video files on his/her local drive and then displays the total duration of all the videos on the site. I've already investigated a few methods that might make this possible: method 1: - only uploading the small chunk (head or tail) of each video file that contains the metadata. - then extracting that metadata and calculating durations. method 2: - pipe each video file with python to ffprobe or ffmpeg on server which can extract duration data. At the end of the day i don't care how its done or what language is used. The main goal is to do this with maximum compatibility of both browsers and video file formats. I am aware, however, that we may have to sacrifice some compatibility in order to make this happen. Duration format can be in total seconds. no need to make any of the display or output pretty. thank you!