When capturing to avi@352x288 (huffy or huncompressed) after I encode (using tmpgenc w/ default settings) to mpeg1 the red colour appears blocky around the edges. But when I encode to mpeg2 the picture is fine (see samples)

http://mytempspace.home.ro/red_mpeg1.mpg
http://mytempspace.home.ro/red_mpeg2.mpg

Anybody know why this is happenning? Is there a way of fixing without using mpeg2?