New grayworld video filter in FFmpeg 5.0

[Arx1meD]

I decided to compare two different methods in the Grayworld filter. If you do not look closely, the difference is almost not noticeable. Or I am doing something wrong again.

so = DSS2("C:\test\underwater.mkv", fps=30.000)
#==========================================================
v1 = so.ConvertBits(32)
v1 = v1.z_ConvertFormat(pixel_type="RGBPS", colorspace_op="709:709:709:f=>rgb:linear:709:f")
v1 = v1.grayworld(cc=0)
v1 = v1.z_ConvertFormat(pixel_type="YUV420", colorspace_op="rgb:linear:709:f=>709:709:709:l")
#==========================================================
v2 = so.ConvertBits(32)
v2 = v2.z_ConvertFormat(pixel_type="RGBPS", colorspace_op="709:709:709:f=>rgb:linear:709:f")
v2 = v2.grayworld(cc=1)
v2 = v2.z_ConvertFormat(pixel_type="YUV420", colorspace_op="rgb:linear:709:f=>709:709:709:l")
#==========================================================
StackHorizontal(so.AddBorders(0, 0, 0, 20).Subtitle("Source", align=2),
\ v1.AddBorders(0, 0, 0, 20).Subtitle("grayworld(cc=0)", align=2),
\ v2.AddBorders(0, 0, 0, 20).Subtitle("grayworld(cc=1)", align=2))

Test video: underwater
Comparison: underwater_test

[Reel.Deel]

@Arx1meD

I don't think you're doing anything wrong. I tried the 2 modes with the "corals" image from here: https://www.eng.tau.ac.il/~berman/Un...orRestoration/



The difference in this image is not day and night but it is visible. Maybe with certain images the difference is very small. For what it's worth, asd updated the docs and added this to the median mode: "This mode is not affected by extreme values in luminance or chrominance."

[cork_OS]

Grayworld effect is unstable on my sources. Is there a way to smooth it temporally or limit its strength?

[Arx1meD]

Cork_os, I think not.
Maybe create a clip with compensation for movement. Something like that:

function MC_Clip(clip clp, int "blksize", int "overlap", bool "chroma", bool "truemotion", bool "global") {
blksize    = Default(blksize, clp.Width()<=720?16:32)
overlap    = Default(overlap, blksize<=16?2:4)
chroma     = Default(chroma, true)
truemotion = Default(truemotion, true)
glob       = Default(global, true)

sup    = MSuper(clp, hpad=8, vpad=8, pel=1, sharp=2, chroma=chroma)
bvec1  = MAnalyse(sup, isb=true,  blksize=blksize, overlap=overlap, divide=0, delta=1, plevel=0, truemotion=truemotion, global=glob, chroma=chroma) # backward vectors
fvec1  = MAnalyse(sup, isb=false, blksize=blksize, overlap=overlap, divide=0, delta=1, plevel=0, truemotion=truemotion, global=glob, chroma=chroma) # forward vectors
backw1 = MFlow(clp, sup, bvec1)
forw1  = MFlow(clp, sup, fvec1)

Interleave(backw1, clp, forw1)
}

MC_Clip(blksize=32, overlap=16, chroma=true, truemotion=true, global=true)
# Your filters are here!
SelectEvery(3, 1)