Does the original N64 Zelda: OoT have small black borders like this or is it my TV accessory?

To connect my N64 to my TV I have to put it through an RCA to HDMI converter.

Are the black borders output from the console or is this added by my TV accessory?

I'm guessing that this is actually padding for old CRT overscan but I don't know for sure.

Solution 1:

The overscan area is a lot larger than you think. CRT televisions were not precision devices. I've shaded the overscan area (technically, overscan + action-safe areas) of your screenshot in red -- that's the area that may or may not be drawn depending on the exact display used.

The black bars are part of the overscan area known as the horizontal blanking area: the period during which the electron beam is moving back to the left-hand side of the screen. Very few CRTs would show this, since it requires both an unusually large display area and a fast beam retrace.

Solution 2:

Looking at some pictures on Reddit, the game doesn't appear to really have those black borders when playing the original N64 game on a CRT screen.