I work on an open-source music sequencer (https://ossia.io) and no later than two days ago I had a fair amount of mails with someone who wanted to know the best settings for his machine to not have any clicks during the show (which are the audio symptoms of "missed deadline"). I've met some users who did not care, but the overwhelming majority does, even for a single click in a 1-hour long concert.
If it's running in a consumer OS (not a RT one) and it counts on having enough CPU available to avoid missing the deadline, that's exactly what soft-realtime is.
Compare your “not a single click in an hour [for quality reason]” to a “not a single missed deadline in 30 years of the life expectancy of a plane, on a fleet of a few thousands planes [for safety reasons]”. That's the difference of requirements between hard and soft RT.
I did some soft real-time (video decoding) and I have a friend working on hard real-time (avionics) and we clearly didn't worked in the same world.
Yeah. To me, hard real time is when you count cycle (or have a tool that does it for you), to guarantee that you make your timing requirements. We never did that.
