[MEncoder-users] Portions of artifacting with libavcodec

[EC]

I have been using mencoder + lavc mpeg4 to encode dvds and for the most
part it has been working out great.

But the output of two recent movies I have done (The Life Aquatic and
Sin City), have had sections where the mpeg4 blocking/artifacting is
horrible.  Everything except these short portions looks perfectly fine.

Here are two examples: http://ec.firetiger.com/blocked1.jpg
http://ec.firetiger.com/blocked2.jpg

In the first movie, this happens in a scene with a lot of fast camera
panning and water, and in the second it is after an abrupt switch to a
rainstorm.  I guess these are tough scenes to encode, but it seems like
it shouldn't be _so much_ of a problem.  Here are the -lavcopts strings
I am using:

-lavcopts vcodec=mpeg4:vbitrate=2000:mbd=2:trell:v4mv 
:cmp=3:subcmp=3:precmp=3:dia=2:vpass=1:autoaspect
-vf pp=de -o ~/Sin_City.avi

Then in latest cvs cmp=3 causes a segfault, so I tried 6:
-lavcopts vcodec=mpeg4:vbitrate=2400:mbd=2:trell:v4mv
:cmp=6:subcmp=6:precmp=6:vpass=1:autoaspect
-vf pp=de -o The_Life_Aquatic.avi

Any hints on how to prevent/get rid of these?

Life Aquatic was done using week or so old mplayer+libavcodec cvs, but
sin city might have been pre7; it was a while ago at least.