Panajev2001a
GAF's Pleasant Genius
Not sure. HDMI is digital, so its ether signal or no signal. Correct me if I wrong. Also artifacts looks like broken/overclocked GPU.
The signal inside is still analog and you do have some self correction built in the protocol to deal with noise and signal loss/distortion but up to a point.
If there is no signal it means that the signal was so full of errors and/or the loss in strength was so high the error correction mechanism could not cope with it. Analog systems may still give you a visible signal in a very crappy way after the digital one gives up so to speak, but it is beside the point I guess.