The volume HUD has always been a pain point for iPhone owners; the fact that it pops up right in the middle of the screen as you adjust your volume is intrusive and becomes a nuisance when you're trying to watch videos or listening to music while viewing photos/reading e-Books.
Countless jailbreak tweaks have been released over the years in an attempt to repair this problem. Most of them move the volume HUD out of the way in creative ways, and now the latest to join that list is HUDPlayer by iOS developer pxcex.