Android device as a webcam but without any third party app or software.

[xebrasaur]

Technically a webcam gives out a signal telling the computer "I am a webcam". To use an Android device as a webcam various apps and their desktop clients create the identity of a webcam. How can I achieve this using software tweaks instead of using some sort of an app and its client? How do I tweak my phone to use its camera as a webcam?