I was in an outsourcing team working for Panasonic door-phone system, the source code was big, but what my team 's done was to develop some more functionalities including video call. It was about ~20 KLOC written in C for the UI & stuff (what we were ordered to do, since the behind layer was not disclosed to us). The source code was a mess since it's written by low-experienced programmers and even intern students. Later I quit that job :)