When I encode with TMPGenc, I sometimes get "noise" in dark areas of the frame.

This is not a motion blocks thing and seems to have nothing to do with motion. It's just in certain scenes of certain movies, I see pixels of "noise" in the dark areas. They are often a very dark red but quite noticeable when played back on my TV.

Doesn't seem to matter whether I encode in MPEG1 or MPEG2 and setting the bitrate higher doesn't seem to fix it either.

Help!