GordianKnot and aspect ratio

[benderman]

I've done a lot of ripps with nandub and now I made my first steps with GKnot. Only (minor) problem is, that I don't understand the whole function of the resolution-calculator.

I select the following:

Input Res: PAL
Input Pix. Asp. Ratio: PAL non anamorphic (4:3)
Crop: disabled
Width: 640

And the resulting hight is 469 (H-Modul=1). Shouldn't it be 480? Same thing happens with 16:9. The calculated res is 640x351 instead of 640x360. The problem could be easily solved by using "Display AR", but I don't understand the function of the both PAL-aspect-ratios.

[Enchanter]

Change the H-modul (And also the W-modul, if you are having similar trouble with the horizontal resolution) to a value of 16 or 32 (or any other factors that does not result in such odd resolutions).

[khp]

Go to the options tab and uncheck 'Follow ITU-R BT .601 Standard'

GK will now aim to hit the perfect 4:3 or 16:9 aspect ratio, on unchopped frames.

[benderman]

Thanx, I wonder if the AR is closer to the original if I leave 'Follow ITU-R BT .601 Standard' checked.

[hacker_on_fire]

by the way if its unchecked 'Follow ITU-R BT .601 Standard' Gknot says it results if the aspect ratio being off by ~2.5%. So should u leave it checked or not?

[khp]

That's one the questions that will probably be discussed untill the end of time. There are numerous lengthy threads on this subject in the GKnot forum at doom9.

As I understand it, standalone DVD players use ITU-R BT .601, but you will get a more precise aspect ratio by not using it.

But again this just my impression, check it yourself using a truely round object in the video.

[benderman]

2.5% seem not to make to much differewnce, but if you use a H-Module of 16 or 32 the resulting hight may differ by 16 or 32 pixel between the two methods. On a 2.35:1 movie at a width of 640 that can be up to 10% (or maybe more). I will always calc with H-Modul=1 and than decide which aspect ratio will be better.

[khp]

Just keep an eye on the aspect error indicator. Or use 'smart chop all' after choppin off the black bars.

[hacker_on_fire]

Originally posted by benderman
I will always calc with H-Modul=1 and than decide which aspect ratio will be better.

I always thought that the Height(modul) should be divisble by 16 and the Width (modul) by 32.

Am i correct by doing dso or should i have:
H = 16 W= 16
or
H= 1 W=16/32

I am confused

[khp]

Originally posted by hacker_on_fire

I always thought that the Height(modul) should be divisble by 16 and the Width (modul) by 32.

Yes, for the most efficient divx encoding, both height and width must be mod 16, and some graphics cards like it better when the width is mod 32.

Benderman just used height mod 1, to test which resolution GKnot would use to get the best aspect ratio.

[benderman]

I many times used H-Module=2 and it it never caused any problems, but it's true that the DivX-codec might compress a very, very little better with H-Module=16. But I think nobody could see the difference. All DivX-codecs I know allow H-Module=2.

[hacker_on_fire]

@ Khp thanx 4 clearing that up

@ Benderman, i tried h=2 and it gives u better es options so u dont have to smart crop all, and still have a perfect aspect ratio.

HoF