First, the rfc is pointlessly complex and optimized for files, not for streaming. if you want to play with it, manage blocks by yourself, ignore the asinine interleaving and block size management.

Second, the algorithm is actually split in two parts, and while the second (generation of repair blocks) is linear, the first is cubic on the number of messages that you put together in a block (~~ matrix gaussian elimination).

And while parts of both encoding and decoding can be cached, I think that "linear time" encoding for raptorq is actually just false marketing speak.

It's a great solution (fast, storage overhead of about 1.2%) iff your data is immutable.