Filters

From Automkv

Place information on filters here.

Removegrain

Removegrain will try to eliminate "noise" or "snow" in the source material.

During recent years it has been fashionable to add noise to the source material to get "documentary-like" feel for the movie/tv series. This kind of noise may be ignored or "tuned out" by the audience but it is not ignored by the compression algorithm. With modern portable digital video cameras the image quality of even "toy" video cameras is practically perfect, so the producers will add noise to the video to meet the expectations of audiences born in 50s to 70s who are used to analog "handicam"-style low-quality portable video cameras.

In practice when you encounter a TV series or movie which has this kind of noise filter applied, you will get inordinately slow encoding that will result in an over sized encode. It is easy enough to identify the applied noise-filter if you're paying attention to the source material; if you see kind of "snowing" in uniform color areas, the original material has noise filter added.

In fact by default xvid/divx codecs will apply noise filter during playback as a "film" effect!

removegrain filter will remove video noise, whether it's intentionally applied or due to poor source material (daddy's 35mm film from Woodstock kept in attic for 40 years..)

From the original removegrain documentation:

mode	sharp edges	corners	thin lines	line ends	thin curves	compression
2	10	10	10	4	10	2
3	10	9	3	1	3	5
5	10	10	10	9	9	2

Since noise removal is by it's nature destructive process, the filter selection will determine a trade off between "smooth" image and preservation of original film detail. As the table indicates, removegrain 5 will provide superior quality, but tends to be slowest and will offer poor compressibility. "3" will compress much better but at the trade off of sacrificing image quality.