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sneaker_ger · 15th January 2013, 19:39

Around here we usually we only speak of dithering in the sense of a method of reducing the bit-depth - which is more in line with what Are_ said than with poisondeathray's post.

Filters like gradfun2db, gradfun3 and flask3kyuudeband do debanding in high bit-depth (i.e. try to create smooth gradients in an already banded source with e.g. 16 bit output) and as a last step do dithering to a lower bit-depth (e.g. 8 or 10 bit). Dithering is to be seen as opposed to simple rounding, which would re-introduce a lot of banding. Poisondeathray's wiki link explains it. Image 1 of the cat is the original high bit-depth image and image 2 would be how the lower bit-depth image would look if we simply rounded down. Image 3 is how the bit-depth reduction looks with dithering.

As poisondeathray said, we have an additional obstacle to overcome, as random noise is extremely hard to compress. If you use Floyd-Steinberg dithering the AviSynth preview might look very good, but after encoding to low bitrate 8 bit h.264 the banding will have re-appeared or originally not existing banding will have been introduced. Methods to limit this effect are:
- switch to 10 bit H.264
- use ordered dithering (gradfun3 or the appropriate parameter if f3kdb)
- increase bitrate (a lot)

15th January 2013, 19:39	#137 \| Link
sneaker_ger Registered User Join Date: Dec 2002 Posts: 5,565	Around here we usually we only speak of dithering in the sense of a method of reducing the bit-depth - which is more in line with what Are_ said than with poisondeathray's post. Filters like gradfun2db, gradfun3 and flask3kyuudeband do debanding in high bit-depth (i.e. try to create smooth gradients in an already banded source with e.g. 16 bit output) and as a last step do dithering to a lower bit-depth (e.g. 8 or 10 bit). Dithering is to be seen as opposed to simple rounding, which would re-introduce a lot of banding. Poisondeathray's wiki link explains it. Image 1 of the cat is the original high bit-depth image and image 2 would be how the lower bit-depth image would look if we simply rounded down. Image 3 is how the bit-depth reduction looks with dithering. As poisondeathray said, we have an additional obstacle to overcome, as random noise is extremely hard to compress. If you use Floyd-Steinberg dithering the AviSynth preview might look very good, but after encoding to low bitrate 8 bit h.264 the banding will have re-appeared or originally not existing banding will have been introduced. Methods to limit this effect are: - switch to 10 bit H.264 - use ordered dithering (gradfun3 or the appropriate parameter if f3kdb) - increase bitrate (a lot) Last edited by sneaker_ger; 15th January 2013 at 19:46.