Why don't desktop computers have realtime subsystems?

[Circlotron]

When I was young, I once played the Alto Saxophone, and today, thanks to that, I'm super sensitive to lip-sync errors in AV equipment to the point that most divx videos give me a headache.

I only recently learned what a clapperboard is used for in the motion picture industry. Visual and audio sync reference.
https://en.wikipedia.org/wiki/Clapperboard

[drussell]

I only recently learned what a clapperboard is used for in the motion picture industry. Visual and audio sync reference.

Dare I ask what you thought it was for? 

[ebastler]

I only recently learned what a clapperboard is used for in the motion picture industry. Visual and audio sync reference.

Dare I ask what you thought it was for? 

Get the actors' attention? 

[Circlotron]

I only recently learned what a clapperboard is used for in the motion picture industry. Visual and audio sync reference.

Dare I ask what you thought it was for? 

I thought it was a meaningless, anachronistic tradition, like when they ring a bell and everyone claps at the closing of the NYSE.