More dither

1 files changed, 11 insertions, 1 deletions

diff --git a/docs/yuv-dither.txt b/docs/yuv-dither.txt
index fa8cd22f..c176ce95 100644
--- a/docs/yuv-dither.txt
+++ b/docs/yuv-dither.txt
@@ -21,7 +21,17 @@ Once we have such a box, generate triangular noise and store it as
 pixels.
 
 Then, use void-and-cluster algorithms to make the Y/U/V noise jointly
-blue.
+blue. This can be done separately for each plane.
+
+A way to look at this operation might be, instead of using
+void/cluster, simply try to minimize the perceptual impact by
+filtering each channel with a perceptually motivated filter and then
+swap pixels until that filter is as close to zero as possible. This
+sidesteps the issue of gray-levels.
+
+The noise quality of doing this may not be good enough though, so it
+could still be useful to do the whole graylevel optimization.
+
 
 Finally, convert to RGB. (Maybe do subpixel sampling?)