Ubuntu (GNOME) default video player name
This isn’t obvious, but the GNOME Videos applications is also known as Totem, and the corresponding package is totem:
ubuntu-bug totem
To find this out, the most reliable way, based on an application’s name in the launcher, is to find the corresponding launcher configuration file. Open a terminal, and run
grep -r Videos /usr/share/applications
This will list /usr/share/applications/org.gnome.Totem.desktop; to find out which package supplies this file, run
dpkg -S /usr/share/applications/org.gnome.Totem.desktop