Why is "cpu=4" always recommended?

[GrofLuigi]

...and not the obvious, "cpu=6" if one wants the best possible quality? "Cpu=4" is recommended in most guides and in most forum posts, but is there a bug or any specific reason why not to use "DERING_Y, DERING_C" as this is apparently the only difference between them? I admit I'm not too knowledgeable about MPEG inner workings, but just from simple logic, since we are deblocking anyway, why not throw everything we have?

Of course I have tried it, and can see no visible difference (may be only my eyes)...

Anyway, I was just wondering.

GL

[Cyberia]

Actually, I skip the cpu= parameter and use cpu2=

It has even finer control.

[Boulder]

I think that CPU=6 is not recommended because most people find the deringing to blur the picture too much.