All N64 games in our videos are recorded from captured footage of a WiiU playing the games in backward compatiblity mode through the virtual console on the system.
The N64 doesn’t output via HDMI natively which is why for this set up a modded WiiU is used as it natively supports HDMI out. The system is set to output at 480p and then using the mClassic HDMI add-on to upscale upto 1080p. You can see in the comparison video the difference mClassic makes for these older N64 games.