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Citizen's Aspect Ratio Calculator Tool for your browser — Page 2

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Fez: I am so excited about Star Whores.
Hyde: Fezzy, man, it's Star Wars.
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I've ripped a few scenes of different PAL anamorphic widescreen 2.35:1 movies (including star wars the phantom menace and gangs of new york) and opened the m2v files in virtualdub mod. The black bars are between 69 and 73 pixels leaving between 430 and 438 pixels for the movie. So 488 is too much.
Fez: I am so excited about Star Whores.
Hyde: Fezzy, man, it's Star Wars.
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For creating anamorphic PAL footage from letterboxed PAL footage I've done a few calculations.

I'd like to try some things out, but have just gotten started with avisynth. Can someone give me an example for a script to do this? Thanks a lot.

That's no moon. It's a LaserDisc.

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Try:

crop(0, 126, 720, 324)
Lanczos4Resize(720,432)
addborders(0, 72, 0, 72)

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Alright thanks. That exactly what came out of my calculation btw:

720/4*3=540
720/16*9/540*576=432

That's no moon. It's a LaserDisc.

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I can't make sense of your calculation; what you've basically done is 576/(4/3). Now if you used 576 because it's the total number of lines in the PAL image, then the method is incorrect. However, the answer is right because, by coincidence, 576 is also equal to the number of active lines in the letterboxed picture 324 * (16/9).

My result was based on 324 * (16/9) / (4/3) = 432.

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This was my train of thought. The original image is 720*576, at a 4:3 aspect ratio. You want to go to a 16:9 aspect ratio of 720*x. If the pixel ratio would match the aspect ratio you would expect it to be as easy as this: 720/16*9=405. But they don't match: 720/4*3 is not 576, but 540. So to go from the aspect ratio to the pixel ratio you'd have to multiply it by 576/540. If you apply that to the 405 you got from the previous calculation you get 432. So there's that. But where did you get your 324 from?

That's no moon. It's a LaserDisc.

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I see what you've done now, you've calculated how to turn a 16:9 anamorpic image into a 4:3 letterboxed image - compress 576 lines down to 432 and add 72-line thick bars top and bottom.

That's not what we're doing here. The image starts off in 4:3 and we want to make it 16:9. To do that it must be stretched vertically by (16/9)/(4/3)=1.333.

After cropping out the black bars with crop(0, 126, 720, 324) we have 324 lines left.

324 * 1.333 = 432.

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I just noticed we were doing the same thing, only I was creating an anamorphic image, original black bars included. Which is something you don't want to do, I know now. 324*1.33=432 and 432*1.33=576 you see? We were just thinking in different directions.

I don't apply the same script on the whole movie btw, because of the vertical shifts. My DVD versions don't have them.

That's no moon. It's a LaserDisc.

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This is a great tool but its giving me an aspect ratio of 720x480 for NTSC 16:9 DVD. Only problem with this is that I have recently ripped a DVD and the original MPEG is 720x480 but to replicate the same ratio when i export it to DVD, i have to create my avi as 720x488.
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Stupid question at this point but can someone explain the "ITU-R BT.601-4 standard"?

In all this years I've never selected the option because the results seem suspect.  When should it be used?

Dr. M

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I can't explain the detail of the standard off the top of my head - something to do with the how digital video is displayed in the analogue realm.

But what it basically means is that 4:3 and 16:9 DVDs are actually 1.368:1 and 1.823:1 (not 1.333:1 and 1.778:1 as you'd expect).

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Yeah, I think I understood that much, but I'm just never sure under what conditions it should be used in the calculator.

Dr. M

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There's no real way to be sure. For example, if you are upscaling a DVD to 1080p, then the standards say you should first crop the sides to leave you with a res of 704* x 480, then upscale to 1920 x 1080.

But this is assuming the DVD was mastered correctly to standards in the first place.

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And I assume then that going from DVD to DVD or HD source to DVD you would not need to check the ITU box?

Dr. M

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From DVD to DVD it depends on whether your source confirms to the ITU standard, and whether you want your output to conform also. Assuming yes and yes, or no and no, then it doesn't matter whether you tick the box or not.

From HD source to DVD, tick the box if you want your DVD to conform to the standard.

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I went back and did some technical reading online about this.  That stuff really makes my head hurt.

I'm still not sure when or where, but I suppose it's becoming less and less important.

Dr. M