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Toning down temporal processing

 
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Kevin Good



Joined: 25 Feb 2015
Posts: 4

PostPosted: Thu Feb 26, 2015 6:25 pm    Post subject: Toning down temporal processing Reply with quote

I guess the two layers of processing are called "temporal" and "spatial"?

In the pop-up I can adjust the "noise reduction amount" and that dials in the spatial NR very specifically.

But outside that window the temporal controls reside. Basically-- I want to be able to tone down the temporal noise reduction. Temporal filter radius of 0 does nothing, 1 is way too much smoothing and things look very artificial. Even turning the temporal filter threshold all the way down, and a setting of 1 on radius looks smoothed-over.

Is there any way to dial in the temporal smoothing more precisely?

Thanks!
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VHSobsessive



Joined: 31 Aug 2011
Posts: 16

PostPosted: Fri Feb 27, 2015 7:17 am    Post subject: Reply with quote

The issue with the temporal filter is that with the threshold turned down, instead of seeing more unfiltered pixels, we see some kind of undocumented spatial filter applied, which kicks in wherever the temporal filter decides to leave a pixel unfiltered.

Clearly it helps to reduce visible noise wherever the temporal filter decides not to apply noise reduction, and therefore improves compressability, but it makes fades look worse (blotchy) than if they were completely unfiltered.

Would be nice to be able to switch this undocumented spatial filter off, it wasn't there in the version 2 demo. Hoping it will be optional in version 3.7 or 4.0.

Another possible improvement is to be able to blend the filtered video with the unprocessed source, using a slider. I think this has been requested before by other users.

My only real criticism of NV is the way fades are handled, it's a wonderful plugin otherwise. Would really like to see this addressed somehow.
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jpsdr



Joined: 11 Aug 2008
Posts: 193

PostPosted: Fri Feb 27, 2015 8:49 am    Post subject: Reply with quote

VHSobsessive wrote:

My only real criticism of NV is the way fades are handled, it's a wonderful plugin otherwise.

Same for me, fades are a little odd, and it seems to be more related to temporal filter than spatial filter. But otherwise, excellent results.
After, handling properly fades and applying a specific algorithm to them may not be so easy as we thought...
First basic issue, proper detection : Do you want 0% of false detection, at the cost of missing some fades, or do you want to be sure to detect all, at the cost of a few % false detection...?
Etc...
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NVTeam



Joined: 01 Sep 2005
Posts: 2238

PostPosted: Fri Feb 27, 2015 9:41 pm    Post subject: Reply with quote

There are indeed two filters, temporal and spatial, just as described in the documentation of Neat Video. There is a complex relation between them that would be too difficult to document. We believe that is not really needed for most uses anyway.

If you see that the temporal noise reduction is way too aggressive (even if you disable the spatial filter by setting the noise reduction amounts to 0%) then the most likely reason for that is an inaccurate noise profile. And the best solution is not to try to tone down the temporal filter itself but to re-built the noise profile to make it more accurate.

Using the threshold for toning down the temporal filter is wrong. Threshold adjusts the way the filter detects and treats moving objects. It is not about strength of the filter in general. In most situations, it is best to not touch this control and use the default value.

We do hear your suggestions regarding blending with original and will likely add that in the next version. There may be something new about fades as well. We are working on that too.

Thank you,
Vlad
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noise reduction for video and photos
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jpsdr



Joined: 11 Aug 2008
Posts: 193

PostPosted: Sat Feb 28, 2015 9:23 am    Post subject: Reply with quote

NVTeam wrote:

If you see that the temporal noise reduction is way too aggressive (even if you disable the spatial filter by setting the noise reduction amounts to 0%) then the most likely reason for that is an inaccurate noise profile.

I thought that if you set noise reduction to 0% (like the "no filtration" preset is doing), you have only the temporal filter, and in that case, noise profile was absolutely irrelevant. Meaning that if you want to do only temporal filtration, you chose any filter profile you have avaible, set "no filtration", and go... Am i wrong ?
If not, it could be good to have an option more "global" to do only temporal, avoiding to have to select a noise profile when finaly not needed.
The case i want to to temporal only is the following. I've a video which was previoulsy denoised, but not excellent. Noise itsel is removed, but large area flicker from frame to frame. A similar result would be to use NV without temporal. So, i want to apply temporal filter on this video, and only temporal.
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VHSobsessive



Joined: 31 Aug 2011
Posts: 16

PostPosted: Sat Feb 28, 2015 3:23 pm    Post subject: Reply with quote

I always switch off spatial noise reduction but for temporal, the profile certainly has an effect. The 'noise level' settings (but apparently not the 'noise reduction amount' settings) also have an effect, though it seems to be subtle.


E2a : the 'noise reduction amount' settings in fact do also slightly affect the temporal filter, I just checked.
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NVTeam



Joined: 01 Sep 2005
Posts: 2238

PostPosted: Sat Feb 28, 2015 8:01 pm    Post subject: Reply with quote

jpsdr wrote:

I thought that if you set noise reduction to 0% (like the "no filtration" preset is doing), you have only the temporal filter, and in that case, noise profile was absolutely irrelevant. Meaning that if you want to do only temporal filtration, you chose any filter profile you have avaible, set "no filtration", and go... Am i wrong ?


Absolutely wrong.

An accurate noise profile is necessary for both temporal and spatial filters.

Vlad
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noise reduction for video and photos
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jpsdr



Joined: 11 Aug 2008
Posts: 193

PostPosted: Sun Mar 01, 2015 12:44 am    Post subject: Reply with quote

Thanks for clarification of this point, it's important.
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jpsdr



Joined: 11 Aug 2008
Posts: 193

PostPosted: Sun Mar 01, 2015 10:54 am    Post subject: Reply with quote

Sorry if i ask again, but i want to be sure to not misunderstood something. If i want to apply only temporal filter, if i'm doing this, is it the correct way :
- Build a noise profile and select it.
- Choose "no filtration" setting.
And start process on video... Wink
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NVTeam



Joined: 01 Sep 2005
Posts: 2238

PostPosted: Sun Mar 01, 2015 11:36 am    Post subject: Reply with quote

Yes, that is correct (selecting the profile is only needed in VD plug-in).

Vlad
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noise reduction for video and photos
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