Old Cathode

An analogue television signal path for Resolume Arena and Avenue. It encodes the picture onto a colour subcarrier the way a broadcast encoder would have, damages the composite waveform as one signal, and decodes it again with a synchronous demodulator that knows no more than a real receiver did. Only then does it paint the result onto a phosphor screen with a shadow mask, a beam that goes soft when it's bright, a curved glass face, and a viewer sitting somewhere in particular.

Nearly everything you'd call the CRT look comes out of that path rather than being drawn on top. Dot crawl happens because the subcarrier sits inside the luminance band. Cross-colour happens because fine detail near that frequency gets demodulated as if it were colour (which is why presenters were told to leave the fine stripes at home). Noise added to the composite gets un-mixed by the decoder along with everything else, so it turns up as grey grain and coloured speckle in the right proportions without anyone asking it to.

In practice the controls interact the way the real thing's did. Dropping the chroma bandwidth smears colour sideways and cuts the cross-colour, because in the hardware those were the same filter. Losing signal costs you the colour before it costs you the picture. Switching from NTSC to PAL changes what the Tint control does, because a PAL decoder averages each line with the one above and a phase error cancels out.

There's also an OpenFX plugin for DaVinci Resolve, Vegas Pro, Nuke and Natron: the same signal path mirrored on the CPU, constant for constant, with the subcarrier phase walk driven by the timeline frame number, so any frame renders the same however the host gets to it.