A hint on choosing the right resolution.

[Fresco]

Good day,

I've done quite a few movies with divX (3, 4 & 5) now and I found a way of choosing a good resolution. It's not based on a compressibility test, but requires much more time (more passes).

The rule boils down to this:

A too high resolution results in a blocky picture.
A low resolution results in ringing effects around sharp edges.
When you have to choose between rings and blocks: choose blocks.

I really hate ringing effects in a movie. Also: postprocessing filters work better at deblocking then deringing.


A procedure to find the good resolution would be:

Do a 2pass rip with high resolution 640.
If it's blocky, lower to 608 and do a new 2pass rip.
If it's still blocky, lower again and do a new 2pass rip.

At some point the blocks will by replaced with ringing effects.
Now the best quality will be the rip with the resolution that preceded the one where the rings first appeared.
Ex: if rings start at 576 res, take the one with 608. It will give the best results without ringing effects.

I hope this helps some people.
Please post your comments.

Fresco

[DJ Bobo]

Are you crazy?! do you think I or any other people have time or nerves to make such a crazy thing?! you talk as if every pass would take only 5 minutes!

Well, I tell you something: if you want less ringing, select a lower max quantizer, that's the whole story!

[Fresco]

Ususally this takes no more then three 2pass rips. After a while you gain a sort of intuition in choosing a good res. I do the econding at night, 2 passes are qeued in Virtual Dub. So it takes two - three nights, and some patience.

I'm sorry if you find me crazy. But if I see that I could get the quality a bit better, I will do a new 2pass session. I hate wasting some of the potential quality.

Another thing, if the bitrate is high (> 940), then try to go for the maximum 704 resolution. Resizing costs quality.

Fresco

[DJ Bobo]

come on man, are you kidding? "only 2 or 3 nights" who are you trying to fool?! one 2-pass encoding session lasts long enough, almost too long for my taste, and you come to say that one should make it "only" 3 times, this is almost 36 hours of power, nerves and time wasting!

Keep something in mind: "the best way is the middle way", so don't be extremist!

[mustaneekeri]

Have u ever heard of GordianKnot and Bits/(Pixel*frame) value? Next time when u have encoded ur DVD 3 times, make a DVD2AVI project file from the VOBs. Load it to GKnot and change cropping and resolution settings to same as ur best rip was, load the audio file(s) in bitrate tab and set the wanted rip size in MB, now watch the Bits/(Pixel*frame) value and write it down.
With ur next rip u can make this BEFORE u encode 3 times and set the res/cropping so u get the Bits/(Pixel*frame) value that u like. That way u got the right res for EVERY movie up front!! It's Magic!! ;)

I have to give u credit tho, i've never seen a guy who goes trough this much trouble to make a good rip. :rolleyes:

[manono]

Yep-

Give the guy credit-he's a glutton for punishment. I'd rather take 15 minutes to run the compressibility test than 2-3 nights to figure the right resolution.

[FranchiseJuan]

I have found that no matter what resolution you use (personally I usually use the Gordian Knot defualt of 640), as long as you get a Bits/[pixel*Frame] value of more then 0.3 (on a two disk rip), the end movie is always good.

No need for a encoding test, no need to worrie, just one little figure to worry about....

[DJ Bobo]

Well mister Juan, this is no thumb rule.

There are some Animes, where you would go up to 0,5 bit/pixel to become a really nice image! (example: Dragon Ball Z)

Other movies are already satured with 0,15 bit/pixel. That means, if you use 0,3 bit/pixel, you'll end up with a size, that is half of what you was expecting.

So you better run a compressibility test, or guess how compressible a movie would be (recent or old video? more or less action? etc)

[rui]

I agree.
I am currently doing an encoding of the movie The Haunting, and in spite that i have a < 0,15 bit/pixel rate, the comp check on this movie is really high (80% plus).
So, i can put it all in 1 cd, with a resolution of 704xXXX, and looking very very good. (i already tested this)

Like bobotns said, there is no "suits all rule". It depends from movie to movie.

[Deptmaster]

Yeah and how much you like the movie aswell, Some deserve 2 CDs other don't.

[PeterTheMaster]

well fresco, you "hint" goes like "if you want the best resolution: try till you have it".
wow! i would never have come up with this idea!