[MEncoder-users] Why use TOOLS/calcbpp.pl and scale ?

[dusty0 at freemail.gr]

I was reading this document:
http://www.mplayerhq.hu/DOCS/tech/encoding-tips.txt

and I have a question to make:

When I do a PAL dvd-rip (using xvid usually) why shouldn't
I use the aspect ratio found in the DVD and use one suggested
by calcbpp.pl ? Almost all the times I have checked up to now,
the good aspect ratio values from calcbpp are smaller than the one
that's inside the DVD.. Won't that lead to a quality loss ?

Furthermore I must also scale the movie to the value suggested
by calcbpp for the aspect ratio that I choose.
I think that scaling leads to quality loss.

It seems that I am a bit confused here. :(
I thought that for a good dvd-rip I should,

1)crop the black borders
2)use the aspect ratio that inside the dvd.
3)don't scale because that leads to quality loss.
4)use a denoiser filter (optional)

Any information/help is welcome. :)

PS:
For my dvd-rips I copy the sound found in the dvd
and I use almost all the times video bitrates from 1052kbps
and higher values.