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Update dvdremux.md
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wiwaz committed May 25, 2024
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While this isn't a comprehensive list of existing standards, anything outside of this table is exceedingly rare.
If the aspect ratio you determined does not fall under one of these, it is almost certainly **wrong**.
While this isn't a comprehensive list of existing standards,
anything outside of this table is exceedingly rare.
If the aspect ratio you determined does not fall under one of these,
it is almost certainly **wrong**.

!!!
Standards go out the window with NTSC -> PAL conversions,
Expand All @@ -260,7 +262,8 @@ then figuring out the transform to make the PAL DVD match.

==- 1. Faded column check

We can the size of black/faded out columns on the image's border, as this can indicate the active area.
We can the size of black/faded out columns on the image's border,
as this can indicate the active area.

![NHK ni Youkoso! 01](https://github.com/guyman624/thewiki/assets/82007920/bee9d99b-c46d-41cf-afb8-546f53da6c89)
Here we have a frame from a DVD.
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Note that the fade on each border can often be off by +-1 pixel,
so we still need to verify this later.

!!!
NTSC has a standard which specifies an active area of 710.85x486,
with 711x480 also being a valid resolution.
Since DVDs are all cropped to 480,
we have no easy way of telling for sure if it's 710.85,
but a good assumption to make
which is extremely similar to 704x480.
A good assumption to make
is that if the disc comes from an analog transfer,
it's more likely to use the 710.85x486 active area.
This check will not be enough to clearly identify the two apart.
!!!

To increase our confidence in these results,
we can combine them with other methods.
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![Logo from Google overlaid ontop of the OP credits](https://github.com/guyman624/thewiki/assets/82007920/f433ef74-1a15-4216-9c0c-d6100ee1df3a)

This show ended up having a SAR/PAR of 4320:4739 (710.85x486 active area),
a difference the faded column check would be unlikely to determine.
a difference the faded column check would be unable to determine.
==-

==- 4. Ground truth check
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