MJPG terrible image quality, no way to adjust

[cash68]

I need to export a small clip as an MJPG avi.   I've adjusted the quantizer from 2 to 20, with no change in file size.  It's always the exact same size, and the image quality is terrible.

[Jan Gruuthuse]

Check settings in 2.6.1 Edit: Preferences: [Video]: Default Postprocessing: unmark
[ ] Horizontal deblocking
[ ] Vertical deblocking
[ ] Deringing

See if this helps?
In 2.5.# these settings are found under: Tools: Preferences: [Video]