Fallback to static image when an input source becomes unavailable

Hi all,

I have a few sources (DVB-T channels) that only broadcast during specific times of the day.
Is it possible (built-in or with an external pipe/script) to show a video or a static image whenever this source becomes unavailable?
It'd be nice to be able to show a "test screen" with a text saying this channel is currently not broadcasting anything instead of the stream just not connecting.