Although in practice you often don't want to do these completely separately. What you want to do is encode the lowest quality as a "base" then medium as extra d

Although in practice you often don't want to do these completely separately. What you want to do is encode the lowest quality as a "base" then medium as extra data that you can add on top, then high as extra data on top of that. This does make the higher qualities slightly less efficient but requires only slightly more data to broadcast different qualities. It would be extra cool in P2P use cases where everyone will be re-sharing the low quality instead of the users with the best connections using a completely separate stream and leaving no good connections to re-share the low quality stream. Of course at some number of viewers in a centralized setup it probably does make sense to send just upload the top quality and make separate lower quality streams for small efficiency gains that add up.