Chroma noise

[Tafflad]

This maybe a simple Q.

Refers to DV capture of old VHS sources, and often its mentioned 'deal with the chroma noise'
How do you identify chroma noise ? what does it look like and how do you assess for example what parameters you need in CNR2 plugin to deal with it.

For example in the John Meyer noise reduction script he has a pair of lines for VHS:

chroma=source.Cnr2("oxx",8,16,191,100,255,32,255,false) #VHS
denoised=MDegrain2i2(chroma,8,2,0)

or is it a case of always applying that adjustment whenever you are dealing with VHS source material ?

[jagabo]

You can view the chroma channels in isolation as greyscale images with UtoY() or VtoY().

[Tafflad]

Sorry to be a bit dense ... but what am I looking for .. in an image and if I use x these commands
I am unsure what is good and what needs fixing.

[DB83]

Always let Google be your friend.

http://www.dxo.com/us/photography/tutorials/mastering-raw-noise

[lordsmurf]

I find the Camcorder Color Denoise filter in VirtualDub to be superior to anything that can be done in Avisynth, when it comes to chroma noise.

[Tafflad]

DB83 - thanks .... I had done some Googling .... many posts pointed here and fixes, wanted to understand the issue and how to recognise & interpret it.

[Tafflad]

I find the Camcorder Color Denoise filter in VirtualDub to be superior to anything that can be done in Avisynth, when it comes to chroma noise.

I had been looking around and came across your post:
http://www.digitalfaq.com/forum/video-restore/565-vhs-chroma-flaws.html
In that you describe use of CNR ..........and the add you now find "Camcorder Color Denoise filter" better, do you run from VD .... if so are default settings good enough or care to advise what are better ?

The 'readme' file gives following:

LoadVirtualDubPlugin ("c:\Program Files\VirtualDub\plugins\ccd.vdf", "ccd",0)
ConvertToRGB32(interlaced=true)
ccd(30,1)

but I can't find any infor as to what the values relate to .... again if you use form Avisysnth could you advise on setings (if those are not ideal)

[jagabo]

The first value is the threshold, the second is the multithreading flag.

[Tafflad]

is it 0= non MT and 1=MT or do I need to set a number of threads?
Can't find any details on this plugin

[jagabo]

You can see how the values relate to the filter by using Video -> Save Processing Settings in VirtualDub. Change a setting in VirtualDub, save settings, then see what changes in the .vdscript file (it's plain text so you can read it with Notepad).

Or do it the other way around. Change the vdscript file, load settings, then see what changes in the filter.

[themaster1]

For commercial tapes in A+ condition (i've tried on many over the years) you have to lower the threshold to 7-10 so ccd(10,1)
in addition of ccd you can use removespotsmc it often help on chroma fluctuations that ccd can't remove (for old tapes generally)
a typical script i use:

avisource()
assumetff()
separatefields()
input=last
U = UtoY().RemoveSpotsMC()
V = VtoY().RemoveSpotsMC()
YtoUV(U, V, last)
weave()
ConverttoRGB32(matrix="rec601",interlaced=true)
separatefields()
LoadVirtualDubPlugin("C:\Program Files (x86)\virtualdubmod1.5\plugins\Camcorder_Color_Den oise_sse2.vdf", "CCD", 0)
CCD(10,1) # from 0 to 100 ; Default =30
weave()
converttoyv12(matrix="Rec601",interlaced=true)

[Tafflad]

You can see how the values relate to the filter by using Video -> Save Processing Settings in VirtualDub. Change a setting in VirtualDub, save settings, then see what changes in the .vdscript file (it's plain text so you can read it with Notepad).

Or do it the other way around. Change the vdscript file, load settings, then see what changes in the filter.

I know this is going to be a real simple Q .... is there a way to zoom in on the image (preview - not change anything) in VD to look closely at impact .. I have looked around menus and can't find a way to 'zoom in' nothing in help file either.

Ignore .... just after posting found the way .. right click on pane .....

[jagabo]

I know this is going to be a real simple Q .... is there a way to zoom in on the image (preview - not change anything) in VD to look closely at impact .. I have looked around menus and can't find a way to 'zoom in' nothing in help file either.

Ignore .... just after posting found the way .. right click on pane .....

Yes, right click on a pane and select a zoom level.

I usually prefer to use Windows' built in Magnifier tool (Start -> All Program -> Accessories -> Ease Of Access). I have it connected to the center button of my mouse. So I can zoom into anything on the Desktop by pressing the center button, another click to zoom back out. You can zoom up to 1600 percent with that.

[themaster1]

To see the differences before/after filtering with avisynth/avspmod (as i believe you don't have superman eyes yet) you can use this:

U = UtoY()
V = VtoY()
Histogram(mode="luma")

[jagabo]

To see the differences before/after filtering with avisynth/avspmod (as i believe you don't have superman eyes yet) you can use this:

U = UtoY()
V = VtoY()
Histogram(mode="luma")

I think what you meant was:

UtoY()
Histogram(mode="luma")

Or:

VtoY()
Histogram(mode="luma")

Or:

StackHorizontal(UtoY(), VtoY())
Histogram(mode="luma")

Or you can just amplify colors of the source:

Tweak(sat=3.0)
StackHorizontal(UtoY(), VtoY())

Or:

StackHorizontal(UtoY(), VtoY())
ColorYUV(cont_y=768)

[themaster1]

yeah i forgot the StackHorizontal part for U&V so like this:

U = UtoY()
V = VtoY()
StackHorizontal(U,V)
Histogram(mode="luma") # or ColorYUV(cont_y=768) #.. thanks jagabo

[lordsmurf]

I find CCD is VirtualDub to be better, yes. CNR has its uses, but not as much these days.

I've never used CCD via Avisynth. But it's verbose. You can test in in VDub, save the settings (.vcf) then read it. It shouldn't be hard to figure out.