QF: is better high (small WxH) or medium (high WxH)

[marillodivx]

Hi! I'm a newbie, and I started encoding togheter a friend of mine. We have differents points of view, and we want to know which is the more suitable for our purposes.
We encode to watch our divx on TV by Hardware player.
consider we encode the same movie on 1 CD (so, same bitrate), with Gordianknot
I do prefer having large size (640xXXX) and so Qf=0.15-0.19 (more or less).
He likes having lower size (512xXXX) and Qf very high (Qf=0.20-0.25).
We can't understand the diference, which one is the best encode.
Can anyone help us? Can you give us some suggestions?
Thanks in advance

[jggimi]

Quality is subjective. What looks better to one person may not look better to another.

The compressiblity of the content will also have a great deal to do with perceived quality. There are no "rules" for specific resolution or specific bitrate, since the results can differ greatly from film to film.

I use the bits/pixels*frames value as a starting point for the first compression test, merely as a guide to help me determine an initial resolution and an initial bitrate. Then, I begin compressibility testing. I ignore the b/p*f value and use the percentages returned by the compression tests.

Based on the results of the test(s), I may alter resolution or the number of CDs I use, alter the resizing method, alter codec options such as bidirectional encoding, and I may add or remove video filters.

If I want to review what the input video will look like, I preview the avisynth script. If I want to review what the video will look like after encoding, I encode individual scenes with the proposed settings.

[Nazgul]

If you're set on using 1CD per movie, then that'll be the primary factor in determining what bitrate you plan to use. Once you figure that out, just run a compressibility test at a resolution you'd like, see where it ends up, then scale up or down from there to get the compressibility that suits your preferences. Some people will tell you less than 75% looks horrid, some will tell you that even 40% can look pretty decent, it's all subjective.

[Mnl]

Also you might want to take a look at AutoGK (http://forum.doom9.org/showthread.php?s=&threadid=64266), which you may or may not already know. This tool automates many of the processes you do with Gordian Knot, like compressibility tests. Just taking a look at how this program chooses resolution and resizing filter based on compressibility tests might give you an idea about how to use compressibility tests yourself.

[symonjfox]

IMO an higher resolution gives sharpen image, but lots of macroblocks when the bitrate is too low.
I tried many configurations up to now, and now I'm sticky to these settings:
Source DVD 720x576

Anamorphic 640x(cropped original vertical res, mod 16)[~640 in many cases] for 1 CD rip.

Anamorphic 720x(cropped original vertical res, mod 16) for 2 CD rip.

Ah, I forgot that Divx hasn't anamorphic support yet, but if they will decide to add it (as 3ivx and Xvid did) these are good settings.
Maybe they will add many blocks (if you watch your movie without postprocessing and staying by the monitor), but if you stay 2 meters far from it and add a simple deblock filter, the image will look great and sharp.