It’s possible to disable the rounded window corners while playing a movie in QuickTime, use the following command to disable them.
Quicktime
Quicktime Player X: Enable auto-play feature
It’s possible to enable the auto-play feature for video files in Quicktime Player X. Use the following Terminal command:
Never display the Quicktime player X title bar
It’s possible to hide the title bar within in a Quicktime player X window. The titlebar automatically shows up when the mouse pointer is active in the window. To disable this behavior, quit Quicktime X and apply the following command:
Keep full screen mode in Quicktime when switching applications
When you are watching a video in QuickTime’s full screen mode and you use cmd⌘ + tab to switch to another application, the movie will automatically exit full screen mode. To stay full screen in the background, use the following defaults write command: