The AVTECH is VERY generic about aspect ratios. Ideally, assuming the ITU values are respected as they should (they generally are, though not always, but it's hard to tell otherwise unless you have something that allows you to be sure), cropping 8 from left and 8 from right gets you the almost perfect 4:3 or 16:9 area (it's an approximation, but a good one). But then it just goes full retard and tells people to resize to 848x480 (actual 16:9 is a bit larger than that), so it might as well tell people to overcrop from 720x480 to something extra rather than just 704x480 (though cropping to 704x480 and resizing to 640x480 is ok).
Obviously, more recent sources don't always need to get all that much cropped, or, sometimes, you'll need to crop more, and obviously you'll need to keep the ratio correct. But with a guide that teaches you to resize to the wrong resolution, you're not going to go too far. Not that many people care since the difference is tiny, but it is there, and for all intents and purposes, it is better to stick with proper math:http://ps-auxw.de/cgi-bin/ar-calc.pl
As you can check for yourself, if absolutely no cropping has been done from the original 720x480 on the DVD, the display aspect ratio is supposed to be around 875x480, but since odd numbers are no go, and since mod2 numbers are in bad taste too for distro, so 876x480 is a good approximation if you need to go with 1.0 PAR. If you, however, do need 848x480, then you'll have to crop to keep the AR. Let's crop before resizing, shall we?
So, in the calculator, first you tell the resolution after the crop, then you can already hit Calculate and check if the Display Aspect Ratio is what you want. In this case, let's try this:
Set the first Transform to Crop: and then set 698, 480. You can set the second transform to resize and 848x480 if you so wish; it's not necessary to specify it in this case, as we are resizing only horizontally, but let's do it anyway. And then you'll see it tells you:
Source resolution: 720x480
Source AR: Widescreen
Final resolution: 848x480
Final PAR: 251280/251167 = 1.00044989986742
Final display resolution: 848x480
Final DAR (square pixels): 8376/4739 = 1.76746148976577
Crop: 698, 480
Scale: 848, 480
So yes, if you want to resize to 848x480, you will have to crop to 698x480 from the original 720, or, in other words, you'll need to:
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, with old-fashioned, non-gamma-aware avisynth's internal resizers:
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So, that's it.
Of course, this is all assuming you ARE using the original DVD (and just used MakeMKV to rip it) instead of downloading some shitty encode that might have done things the wrong way for all we know ─ and thus there is not way to be sure we are doing the correct thing if whoever ripped it fucked something up, like for example cropping just what necessary, then resizing to 720x480 or 704x480 and flagging as if this was the perfect 16:9 area.