Delowpassing guide
As video encoders, sometimes we have to deal with images that have been blurred from their original state in some way. For example, a Blu-Ray authorer may blur a master before putting it on the disc in an effort to reduce encoding artifacts (since at identical bitrates, blurry content is easier to encode accurately than sharp content). In the context of anime, any type of blur is destructive, and so seeing an authorer choose to do this is painful. Here is a real-world example—the blurrier image is a screenshot from the Japanese Blu-Ray, and the sharper image is more or less how the original artist drew it.
Normally, it is impossible to recover information from a blurred image. However, there is one specific way to undo a blur: If you have the original unblurred image and you know the precise blurring process the authorer used, you can use the unblurred version of the image to recover the detail lost in the blur.
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