Sample Aspect Ratio calcutions

[jmk]

well, i had my biggest problem with "2001: A Space Odyssey" i took my quite a while to figuere the correct ratio out.

it is encoded on the dvd as:
Aspect_Ratio=16:9
Picture_Size=720x576

but you have to crop it in this way:
crop(2,52,-2,-52)

which left me with a ratio of 2,16:1. which is quite a difference to 2,35:1, the value megui proposed...

but also a couple of other movies are not really 2,35:1 some are more close than others, but if i set the par/sar/or whatever value, i want it to be exact!

[nm]

Actually 2001: A Space Odyssey was shot in 70mm film with aspect ratio 2.21:1. In DVD releases there are usually narrow bands of image missing from all sides (perhaps because the transfer was made from a 35mm 2.35:1 copy), but at least Amazon lists 2.21:1 as an aspect ratio for their 2001 DVD releases.

[SeeMoreDigital]

Yep some are wrong...

My copy of Lawrence of Arabia is described on the back of the DVD as being 2.20:1, when it's nearer to 2.157:1.

And Dune, which is described on the back of the DVD as being 2.35:1, when it's nearer to 2.30:1.

Which both equate to being around 10 vertical pixels off target... quite a bit :scared:


Cheers

[jmk]

Actually 2001: A Space Odyssey was shot in 70mm film with aspect ratio 2.21:1. In DVD releases there are usually narrow bands of image missing from all sides (perhaps because the transfer was made from a 35mm 2.35:1 copy), but at least Amazon lists 2.21:1 as an aspect ratio for their 2001 DVD releases.

yes, and imdb.com lists it as 2.20:1 but it looked awful. a literally took a ruler and measured the visible picture on my computer screen - that was fun :)

all i am trying to say here, even though the ratio of the actual picture (what did we call it again) might be off, if the par/sar/whatever value is calculated correctly, it does not matter.

jmk

[SeeMoreDigital]

yes, and imdb.com lists it as 2.20:1 but it looked awful. a literally took a ruler and measured the visible picture on my computer screen - that was fun :)Well nobody should have to do that for a start!

The more convenient method would be to: -
Play your DVD source in your favourite software media player "at full screen". (Not WMP 9/10).
Navigate to a nice light section of the movie, and press the "Print Screen" button on your keyboard.
Paste the captured image into a reasonable quality imaging software application.
Use the "auto cropping" tool in your imaging software application.
Save the cropped image and make a note of it's "pixel frame size" (PFS)
Grab a calculator and divide the pixel image frame "width" by the pixel image frame "height".

The resulting calculation will be your "Movie Aspect Ratio" (MAR) ;)


Cheers

[jmk]

well, you could just use the values provided by the d2v and the avs file -> and thats what my tool does.

the new version prints it out, too. and it should now work with every resize method

till it gets approved:

http://rapidshare.de/files/12751934/ar_calculator_0.2.rar.html

[SeeMoreDigital]

Okay,

Here is the first version of the ARS Calculator. I hope some of you guys will enjoy using it :)

https://i.imgur.com/dshbLYR.png

Download Link: https://forum.doom9.org/attachment.php?attachmentid=5451&stc=1&d=1139749825

At the time of writing it requires version 2 of Micro$oft's .NET Framework in order to run.

My profound thanks goes to Moitah. Who was able to turn my design concept into a working reality. Many, many thanks....


Cheers

[jmk]

hey, nice design.

correct me, if i am wrong, but it should only work with pal dvds!?

jmk

[SeeMoreDigital]

hey, nice design.

correct me, if i am wrong, but it should only work with pal dvds!?

jmkNope..... It will generate an "Aspect Ratio Signalling" value (aka: PAR, SAR, DAR value) for both PAL and NTSC encodes ;)

[Seb.26]

Hum ... long & interesting post ! :)

so I've a question : is my way is right or fully ...bad... ?

My way :

For both PAL and NTSC DVD, I just crop up and bottom ( if side borders are not too large ;) ) ... never resize !

And I know :
> PAL : 720*576 -> 1024*576
> NTSC : 720*480 -> 854*480

So if my cropped frame is 720*416 (PAL) for exemple , my AR in MkvMergeGui is 1024*416 ...

is it right or not ?! :scared:

Thanks everybody :)

[SeeMoreDigital]

If we are not following the ITU specification to the letter, which most (if not all) software players, don't appear to follow.... then the answer is yes ;)

[yaz]

sorry for my lame kick in, again. maybe i'm a dumbass but i feel some 'overcomplication' here. imho, u don't need anything else than the par value for making correct resizing.

the equation considered is :
dar = par x sar
where
dar : display aspect ratio (what ratio to be displayed)
sar : stream/sample aspect ratio (the original/non-cropped aspect ratio of the stream)
par : pixel aspect ratio
note, these all are given if your source can be played correctly !

actually, par is a multiplier giving how much the image must be expanded horizontally so as to get the correct/intended dar. that's what all players (should) do.

if the stream is cropped (whatever way !), the resulting dar value stays correct if the same par is used for resizing. of course, the picture will be higher or lower but not distorted.

it's quite easy to demonstrate. take your favourite dvd, make some different arbitrary but player compliant (say, mod16) cropping and than some short anamorphic encodes. (to go up to the studio logo is far enough for checking) set par value according to what shown on the dvd cover (can be 4:3 or 16:9only !). won't see any ratio distortion. (if someone would tell me how to upload images to doom9, i would show some demo pics, but it's worth to try personally ;) )

the bests
y

ps if i get wrong what u're talking about, pls, forgive me :confused:

[Seb.26]

If we are not following the ITU specification to the letter[...]
Please : Where could I read some papers about that ? ... I don't know what is it :o :p
[Edit] -> I will read all on your www ;) ... it looks great ! :)

[...] then the answer is yes ;)
Ok, so I'm not fully idiot ... :D ;)

My way looks really simple beside all your heavy-sci-math-computing :D :D

So if I'm wrong for 1 ou 2 pixels in height ... what the matter ?! ;) :D :o

Thanks for answer SeeMoreDigital !
( from where is your avatar ? a movie, but which ? )

[SeeMoreDigital]

( from where is your avatar ? a movie, but which ? )It's from a TV show called "House" (http://www.tv.com/house/show/22374/summary.html?q=house)


Cheers

[Seb.26]

;) thanks.
Seb

[orion44]

If you can guys, try and calculate "everything" as a fraction, because converting fractions to decimals and back to fractions again "can" produce conflicting Aspect Ratio Signalling (ARS) values.

If your NTSC movie has an aspect ratio of 1.33:1, then this can be represented as a fraction of 4/3. Meaning: -

4 480 1920 8
- x --- = ---- lowest dominator - Giving an ARS value of 8:9
3 720 2160 9

If your NTSC movie has an aspect ratio of 1.77:1, then this can be represented as a fraction of 16/9. Meaning: -

16 480 7680 32
-- x --- = ---- lowest dominator -- Giving an ARS value of 32:27
9 720 6480 27

If your NTSC movie has an aspect ratio of 1.85:1, then this can be represented as a fraction of 37/20. Meaning: -

37 480 17760 37
-- x --- = ----- lowest dominator -- Giving an ARS value of 37:30
20 720 14400 30

If your NTSC movie has an aspect ratio of 2.35:1, then this can be represented as a fraction of 47/20. Meaning: -

47 480 22560 47
-- x --- = ----- lowest dominator -- Giving an ARS value of 47:30
20 720 14400 30

If your NTSC movie has an aspect ratio of 2.40:1, then this can be represented as a fraction of 12/5. Meaning: -

12 480 5760 8
-- x --- = ---- lowest dominator - Giving an ARS value of 8:5
5 720 3600 5


For working out the "Aspect Ratio Signalling" values of PAL sources, simply substitute 480/720 to 576/720 and recalculate.

The same formula can be used to work out the "Aspect Ratio Signalling" values of cropped and re-sized encodes too by entering the relevant resolutions.


Cheers
Thank you!

This helped me a lot. :D