Grain Is Not A Defect: How Eugenics Improve Video Quality
“Way to grainy/noisy for a 1080p… I’ve seen better BRRips @ 2gb…”
As the above quote shows, a lot of people are under the impression that grain is the same as noise, and is a defect. Not just in the scene, which is already known for being incredibly dumb, but also in the AMV and fansub communities. Over the past few months, fansubbers have slowly come to terms with grain (with a few notable exceptions) and at times have gone a little too far such as adding grain for no good reason. Granted adding grain is at times necessary but trolling with it is a bit much. Before the community even thinks about how much grain is necessary though, I think the various video scenes need to get over the fact that it is NOT a bad thing.
This might come as a surprise to some but grain makes up a large amount of picture quality. Most video is encoded with DCT codecs which break things into macroblocks. Without grain or anything else detailed and small, the quantizers the various codecs use will smooth out the blocks and produce solid colour bodies, something x264 overcomes with it’s adaptive quantizer. On content such as animation, large flat colours can be how it’s meant to look, but that is certainly not the case with live footage. Another problem is that where there are large solid blocks, a quantizer might be a bit over active and smooth out a very minor gradient, often seen as grey/white blocks and lines in the sky on a clip. Something like an adaptive quantizer really helps with that, but so does the minor amount of grain often present in sources.
Noise on the other hand is usually the product of poor capturing and is an issue in the source. If a source is noisy, then naturally you denoise it. Grain however can be reduced, added, or left alone, depending on how much there is. One simple way to tell if your clip has noise or grain is by the shape, size, and distribution of it. Grain tends to be uniform and rather fine, except for in flashback scenes in anime where it is significantly larger, and it almost always covers the entire picture. Noise often just impacts a small part of the picture, is usually bigger than grain, and the noise ‘chunks’ are irregular. Paying close attention to grain will show that it appears quite regular. Digital grain is often static as well, so it doesn’t move between frames. It’s easy to spot if you look at a slow pan, the image will pan under the grain. Noise however will move in every frame. Noise also sometimes shows up as a colour aberration.
Dirt is a type of noise, and is quite rare in modern content. It is usually found in analogue content transferred to digital, mostly on older things, and sometimes in video that has already been compressed badly. I have seen it almost nowhere in live content but in anime it’s often present around hair edges. Usually edge cleaning will fix it, and if you have dirt but no other noise there is no reason to denoise your entire clip, just mask it and clean it, or use a dedicated edge cleaner filter.
To get back on track, grain is not bad. Complaining about grain makes you look dumb and blind, and getting rid of it makes content look sterile as hell. Fine grain actually looks good, is rarely even noticed, and makes a picture look significantly more natural. There is absolutely no need to remove or tamper with it. The problem is that people are stupid. I’m not going to actually talk about selective breeding but I think the title gets the point across. There are lots of good uses for grain, such as debanding without resorting to dither, which gets banded at the quantizer anyway, and overall it does look better. Now stop fucking with it.