incorrect CPU usage readings in 2.2.19prex?

[safemode]

Is there something generally wrong with how linux determines total cpu
usage (via procmeter3 and top) when dealing with applications that are
threaded?   I routinely get 0% cpu usage when playing mpegs and mp3s and
some avi's even (Divx when using no software enhancement) ... Somehow i
doubt that the decoders are so streamlined that they produce <1% cpu
usage on the computer.  Does anyone know what's going on with this?
ps shows nearly 0% cpu usage in the threads as well.
    i've seen it in these programs
        freeamp
        mplayer

I've seen it in earlier 2.2.19 kernels but i'm using pre14 right now.