Since phpBB 3.2.0, support of the outmoded media file formats (such as WM, RM and QuickTime) has dropped.

However, the JavaScript function "play_qt_file" is still present inside the forum_fn.js file (included in proSilver templates' folder). Its purpose is: Play quicktime file by determining it's width/height from the displayed rectangle area. What's the point since phpBB 3.2?

I suppose it's just a relic from phpBB 3.1, and it no longer makes sense to keep it. I already mentioned that fact on the phpBB board >>> https://www.phpbb.com/community/viewtopic.php?f=591&t=2408416