Could you please elaborate on that? Is it a general problem - and at what level is "low" considered to be?
Your rough run-times listed (acknowledging that they are not benchmarks) do indicate UMC being several % slower than Media SDK in SW mode. Even using the usual grain of salt, are those numbers indicative (given the stream, resolution, processor etc.) of the difference in performance between UMC and Media SDK SW?
By the way, perhaps this discussion would be better to move into a seperate thread with appropriate topic...