A video mixer a-la Blackmagic ATEM Mini will do this. Maybe there are cheaper options if it's just being used for input switching.

That will introduce a lot of delay - they make synchronous cuts by frame buffering every input.

Then I'm afraid it's not possible. The reason the input switch takes so long is because of the HDID negotiation.

A video mixer acts as the source and sink for the output and the inputs respectively, where a HDMI switch will just physically disconnect and connect the output port to a different input port, meaning the HDID negotiation has to be re-done every time.

FWIW, I don't care if the screen briefly flickers during switching.

You just need to strip the hdcp on the source.

It still seems the right hardware, upstream or downstream depending on which direction you're viewing things from, could keep the connection alive with the HDID pre-negotiated. Like, assume the hardware doesn't change between switching. If you're the TV's firmware and have the CPU power to, why renegotiate when switching inputs. Solve for the default case and have it standing by and running hot. it's not like the panel is going to change in the interim.

> switch between inputs within 50ms

Why do you need this?

What kinds of inputs?

How many?

Are they all operating at the same resolution and frame rate?

What resolutions?

Do they require scaling? De-interlacing?

Are they synchronized? (genlock)