With a small catalog, you can pre-encode everything. That means that in the unencrypted case, media files can be sent directly from the kernel's page cache, as

With a small catalog, you can pre-encode everything. That means that in the unencrypted case, media files can be sent directly from the kernel's page cache, as unmapped I/O. Eg, the data is not even touched by the CPU. But in the encrypted case, you're suddenly touching every byte with the CPU, thereby doubling your memory bandwidth requirements. With a large catalog like YouTube's, I would expect that most of the titles are saved in some master format, and are encoded on the fly. That means that the data is already being touched by the CPU to re-encode it on the fly for whatever format is needed by a particular client. My expectation is that if YouTube was re-encoding on the fly due to the catalog size, they would suffer less of a CPU hit than Netflix did, so SSL would be "easier" for them to implement.