"Temporal filter threshold" does the opposite what

questions about practical use of Neat Video, examples of use
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Felix
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Joined: Fri Jul 13, 2012 12:06 am

"Temporal filter threshold" does the opposite what

Post by Felix » Sat Jul 21, 2012 5:54 pm

Hi,

the manual says:
The Temporal filter threshold setting determines how sensitive the temporal filter is to changes (for
example, motion of objects) in consequent frames. Higher values of this setting lead to more aggressive
filtration with less attention to temporal changes (lower motion sensitivity). Lower values lead to less
aggressive filtration
with more attention to temporal changes and better preservation of moving details
(higher motion sensitivity).


So as I understand it, if I set the threshold from 100 (standard) to 0 there should be less noise reduction. But it´s exactly the opposite.
0 smoothes out all noise while 300 only removes very little noise.

Pictures:

Threshold 200 (Filter 0% luminance, 0 % chrominance, radius 1):
Image


Threshold 0 (Filter 0% luminance, 0 % chrominance, radius 1):
Image

So if I want less noise reduction, should I increase the threshold (just like with typical unsharp mask filters)?

Premiere CS5.5

NVTeam
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Post by NVTeam » Sat Jul 21, 2012 7:03 pm

I have just checked the filter in Premiere: the threshold control works for me as described in the user guide. If you get the results that go against the description of the control in the user guide then it is quite likely that the noise profile you use is not accurate.

If you want to adjust the amount of noise reduction, changing the threshold is not the right control at all. The threshold is intended to help you adjust the quality of noise reduction, not to adjust its strength. So if you want to adjust the strenght (amount) then I recommend to leave the threshold on default and adjust the controls that are more directly related to the strength: the noise reduction amounts of the intra-frame filter (in the main window of the plug-in) and the temporal filter radius.

Also, I highly recommend to start with the noise profile - double-check that it is built correctly. Please see the video tutorial.

Hope this helps,
Vlad
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sat Jul 21, 2012 7:18 pm

Thanks for your answer. The noise profile was an auto profil but got 96%.

I checked everything again and my observations are:

If you set the threshold to 0, the motion details are perfectly kept but the noise reduction is stronger.

With a threshold of 100 or higher, motion detail gets more and more distorted but the noise reduction is weaker.

Thing is, Neat Video just works to good with my footage.
I have ISO 3200 AVCHD footage from an FS700 which is pretty noisy and even 0 luminance und 0 chrominance noise reduction with temporal radius 1 and threshold of 100 is too strong! It removes almost all the noise/grain.
So I raised the threshold to 200 but that has a negative effect on motion detail, as the manual says.

I just wonder why a threshold of 0 not only keeps all/more motion details but the noise reduction is also increased. I don´t understand the "mechanic" behind it.

NVTeam
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Post by NVTeam » Sat Jul 21, 2012 7:31 pm

Well, me to, I also do not know why it goes against the user guide. A possible reason is a problem with noise profile. Or perhaps there is something unusual about the footage itself. That is difficult to tell without seeing a reproducable test case. If you can prepare a test project with one short clip and send it (project and clip) to support [at] neatvideo.com, we will directly check what is going on and then the cause should become clear.

Thank you,
Vlad
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sat Jul 21, 2012 7:52 pm

email is being sent right now. Should take 15 minutes.

To sum it up:

1) Noise reduction is very strong even with 0 % noise reduction.
2) Threshold works not as it´s supposed to work.

Edit: The mail blew up your mail server. I´m uplosding it to my webspace...^^


NVTeam
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Post by NVTeam » Sat Jul 21, 2012 9:03 pm

Thank you, I have downloaded the files, we will investigate.

Re: 1) Noise reduction is very strong even with 0 % noise reduction.

It is strong because the temporal filter radius is not zero. Set it to zero to disable temporal filter.

Vlad
Last edited by NVTeam on Sat Jul 21, 2012 9:05 pm, edited 1 time in total.
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sat Jul 21, 2012 9:05 pm

I found something that might help you.

All the noise reduction seems to result from the temporal filtration. Inside the Neat plugin preview there is now noise reduction when set to 0%.
But then in the premiere preview the noise reduction is severe.

Regarding the footage. That´s just some nonesene in ISO 3200 to test High ISOs in the most crappy lighting situation.
Last edited by Felix on Sat Jul 21, 2012 9:07 pm, edited 1 time in total.

NVTeam
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Post by NVTeam » Sat Jul 21, 2012 9:07 pm

Which is by design. The preview inside NV window shows the result of the intra-frame filter only. The preview in Premiere itself shows the results of both intra-frame and temporal filter. So that is normal.

Vlad
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sat Jul 21, 2012 9:15 pm

Ok, thanks a lot for the explanation.

Is it a good idea to disable the temporal noise reduction?
When I do that I have to raise the luminance noise reduction from 0 to 50 % to get simmilar results.

Isn´t the temporal reduction a more efficient way and degrades the picture less than the normal noise reduction?

NVTeam
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Post by NVTeam » Sat Jul 21, 2012 9:20 pm

The clip is not very noisy so it doesn't need a lot of noise reduction, but still disabling the temporal filter is not really needed in my opinion. I think the noise reduction is adequate and the result looks quite good with the radius=1 (all defaults there; and the intra-frame filter is disabled) in your test project. I recommend to just use these settings. That should be better than disabling the temporal and using only the intra-frame.

Vlad
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sat Jul 21, 2012 9:27 pm

Ok, and what about the original issue. 0 threshold reduces more noise than 100? Is that normal, too?

If so, my suggestion would be to add an additional controller to adjust the temporal noise reduction level in a future release, not just on and off (0 frame, 1 frame)

Those new cameras, F3, FS100, FS700 are so low noise and denoise so well that it would be cool to adjust the temporal reduction more fine.

NVTeam
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Post by NVTeam » Sat Jul 21, 2012 9:47 pm

Felix wrote:Ok, and what about the original issue. 0 threshold reduces more noise than 100? Is that normal, too?
No, that is not. We will investigate what causes such an effect with that clip.

Adjusting the temporal noise reduction amount could indeed be useful in some cases.

Vlad
Image Image Neat Video team
noise reduction for video and photos

NVTeam
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Post by NVTeam » Sun Jul 22, 2012 11:17 am

We figured it out. The behaviour of the plug-in in those circumstances is still normal, but not very obvious. When you move the threshold to the extreme low values, the temporal filter is not always applied (low threshold stops it) and to compensate, NV applies spatial filtration instead. This is done to improve the overall visual quality in normal circumstances. The same behaviour of NV causes that effect which you observed when threshold=0 (which is of course not normal circumstances). That is not fully documented now, we will need to address that.

To summarize:
1) do not set threshold to 0 or close to 0; that is not useful in most cases; if you are not sure, better leave it at the default value;
2) to adjust the strength of the intra-frame filter use noise reduction amount controls in the main window of Neat Video;
3) to adjust the strength of the temporal filter use the radius setting and/or blending with the original clip (the latter is done using the controls of the host application).

Thank you,
Vlad
Image Image Neat Video team
noise reduction for video and photos

Felix
Posts: 12
Joined: Fri Jul 13, 2012 12:06 am

Post by Felix » Sun Jul 22, 2012 1:10 pm

Blending with the original clip!
That´s a great idea, will try that out. :D


Thanks a lot (!) for looking into this so quickly and thoroughly, great support!

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