This is the best explanation of this that I've yet seen. Very well done.

It seems to me obvious that the software "machine" which encodes or decodes video should be a patentable device. The trouble has less to do with patentability of software in general, and more with a) the lifespan of the patents, b) the ease with which they are acquired, and c) the time and money required to oppose and strike down a patent which should never have been granted in the first place.