I'm still looking for a monitor that can switch between inputs within 50ms. Should be possible, no?
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.
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)