DV denoiser?

[bb]

When shooting at low light conditions I get a lot of small dancing dots in red, green, and blue. The video doesn't look too bad, if you watch it from a distance, but for a cleaner picture and for encoding I'd like to get rid of this special sort of noise.

Does anybody know a good filter? I tried the old and the MMX denoiser for VirtualDub, Donald Graft's smart smoother, and a bunch of others, but the result wasn't convincing.

Thanks for suggestions.

bb

[bb]

Ok, I tested several filters in the meantime. Here are my results (if anybody is interested...):

Best way to get rid of the color dots is the following combination of filters:

1. chroma noise reduction (found it through Donald Graft's fabulous site)
Luma 15.98%, 85.16%, Wide
Chroma1 20.98%, 100%
Chroma2 20.98%, 100%

2. dynamic noise reduction (MMX) (= dnr2)
8

3. resize (Precise bilinear) (comes with VirtualDub)
640x480


bb

[Corrado]

Thanks a lot, I'll try the combination with my DV shots the next time I encode.

Which format did you use for the final movie? DivX? Did it make some difference as far as noise reduction is concerned?

PS: why reduction to 640x480 (Aspect Ratio 1.33)? Your DV PAL material should be 720x576 (AR 1.25), right?

Corrado

[bb]

Hi Corrado,

yes, I used DivX4. AR is intended to be used for PAL, which is 4:3. So if you want to watch it on you computer screen without distortion, I think 640x480 is all right: pixels on the computer monitor are square while TV pixels aren't. BTW: sometimes I use 640x360, which is for 16:9 (my camcorder has a 16:9 mode). But I'm not sure about this, I'll have to check it again. Anyone else?

Noise reduction is done before encoding, but depending on the codec settings the final picture might be more or less blurred, which has an impact on the noise as well. It's necessary to reduce noise as much as possible before the codec comes into play, because noise will influence motion tracking negatively. With lots of noise you'll get larger files, and the quality will be less.

The problem is to get rid of as much noise as possible without loosing too much sharpness. Spatial or temporal smoothers didn't give good results in this case.

bb

P.S.: If your DV is interlaced, use Donald Graft's excellent smart deinterlace before the other filters, either through AviSynth or directly as a VirtualDub filter (I don't think this would change the performance, because we have to use RGB anyway).

P.P.S.: If you use VirtualDub's "File / Save processing settings" feature you must be aware of the fact that the dynamic noise reduction filter looses its settings. That means, after "Load processing settings" you'll have to set the dnr filter to 8 manually each time.

[Corrado]

Originally posted by bb
If your DV is interlaced, use Donald Graft's excellent smart deinterlace before the other filters, either through AviSynth or directly as a VirtualDub filter (I don't think this would change the performance, because we have to use RGB anyway).

I wonder if we can use the "chroma noise reduction" and the "dynamic noise reduction" filters in YUV color space through AviSynth script.

If yes (or if there're equivalent filters for YUV), then both resizing and deinterlacing - with GreedyHMA - can also be used in YUV and the speed will be higher.

Corrado

[bb]

If I had found something appropriate, I would have posted it, because I prefer the AVISynth way, too. I even tried to use the VirtualDub filters through AVISynth, but that was slower than using them directly in VirtualDub (maybe because of the necessary ConvertRGB?).

If you find a good YUV chroma denoiser, don't forget to tell me ;)

I didn't find a YUV equivalent to the dynamic noise reduction either. That filter really bothers me, because the programmer must have forgotten to implement a "configure" method. That's the reason why "Save processing settings" doesn't work with this filter.

bb

[neuron2]

Didn't you guys see the scriptable version of DNR that I have at my site? http://sauron.mordor.net/dgraft

[bb]

@neuron2:

Thank you, will test it this weekend. BTW: is your dnr version MMX optimized like dnr2?

On your "Other Filters and Tools" page there is the Chroma Noise Reduction filter which gave me good results. I don't see how I could use it through AVISynth.

Thank you very much for your amazing filters. My favourite is the smart deinterlacer filter, which I use a lot for TV captures.

bb

[neuron2]

@bb

Yes, it is the MMX version.

Smart Deinterlacer is both loved and hated by many. :-)