How does youtube encode videos?

Question

I am interested in knowing how does youtube provide different quality video content. ie do they store different versions of the same video or do they have multi-layered video encoding or what is the deal here?

is there a place i can get some resources on this? papers/whitepapers etc.

Thanks!

Answer 1

I found that a lot of work has been done using H.264/SVC encoding to deliver multilayer video for variable bitrates to accommodate different bandwidth of the user.