Calculate the Aspect Error

[Dark-Cracker]

What is the calcul for the aspect error ? (it seems to me it use the ration and the width*height

How could i find the new width*height with the correct aspect error ?

PS: plz don't say me correct it with Gknot, i search HOW to calcul it.

PS2: sorry for my crap english

[HotSpur]

1. When using GKnot first find out if your movie is 16:9 or 4:3. I usually drag the slider and look at 1 or 2 scenes to verify it looks correct (not stretched out or squished). Make sure you select View / Resized when you open the .d2v file.

2. Under Resolution tab in GKnot look at the aspect error % and resize so it is as close to 0 as possible. Movies have different aspect ratios so don't just use a formula because it depends on the movie. (For example, I just encoded a movie with 2:1 aspect ratio!)

3. See Doom9's guide to resolution it's under guides / divx / divx3 / bitrate & resolution - it should give you more info than I could :)

[Nic]

Hi,

with:
"How could i find the new width*height with the correct aspect error"

Do you mean resizing? or smartcrop? Any which way, my dvd2avi, handles both these the same way as gknot, and when its released (soon!) the source will be released too...so you can just grab it from there :)

Cheers,
-Nic

[Dark-Cracker]

i mean a "smartcrop all" fonction.

Ps: does the gknot crop/resize fonction work with all dvd ratio ? (1.33 / 1.44 /1.77 /1.85 /2.35 ...) or only with the 4:3 (1.33) and 16:9 (1.85) and 16:9 anamorphique (2.35) ?

what are exactely the words : letterbox / wildcine ?

[manono]

Hi-

There are only 2 DVD Aspect Ratios, 4:3 and 16:9. The numbers you gave are for the movies themselves. But yes, GKnot works with them all. It doesn't matter-full screen, wide screen, letterbox, anamorphic, GKnot handles them all.

[GodH8sMe]

I think he's asking for the calculation that generates the aspect error percentage guys.

[Therion]

Aspect error is the %-difference between the aspect-ratio after cropping and the aspect-ratio after resizing.

I believe the formula goes like this:

Example:

PAL movie 720x576
16:9 aspect ratio
left+right crop = 10
bottom+top crop = 150

crop_aspect = (576/(576-150)) * ((720-10)/720) * (16/9)

resize_aspect = [resized width] / [resized height]

aspect_error = ([crop_aspect] - [resize_aspect]) / [resize_aspect]

[DaveEL]

Input Width = 720-Crop Left - Crop Right


i think these are right

Input Height NTSC 4:3 = (480-Crop Top - Crop Bottom)/(10/11)
NTSC 16:9 = (480-Crop Top - Crop Bottom)/(40/33)
PAL 4:3 = (576-Crop Top - Crop Bottom)/(82/75)
PAL 16:9 = (576-Crop Top - Crop Bottom)/(328/225)

Input AR = Input Width/Input Height

Output Ar = Output Width/Output Height


AR Error = 1-((Input AR)/(Output AR))

DaveEL

[skipper152]

You might want to check out this thread:

http://forum.doom9.org/showthread.php?s=&threadid=23439&perpage=20&pagenumber=2

wef has some code about the aspect ratio and error somewhere in the middle of the page; also includes about non-anamorphic and anamorphic and ITU information.

skipper

[llemor]

DaveEl's calculation is correct.

I'm using the same method and it also similar to GKnot's calculation.;)

[DaveEL]

[QUOTE]Originally posted by llemor
[B]DaveEl's calculation is correct.


good to know its means my software works correctly too :)

DaveEL

[Therion]

I forgot to mention: my formula is correct when you use gknot without using the ITU-R BT.601 Standard. :D (As in Everwicked's guide).

If you follow this standard the other formula is correct. You will see the input aspect-ratio change when checking/unchecking this option in gknot.