Reverse sharpen footage in Resolve, is it possible?

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Umberto Uderzo

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Reverse sharpen footage in Resolve, is it possible?

PostWed Feb 28, 2018 10:18 pm

I'm currently using Fusion to patch a bunch of clips from oversharpening.
I simply subtract a blurred version of the frame from the real frame and use this difference as a patch to fix the oversharpen (partially).

But using Fusion for this simple task is annoying because this means that i need to transcode all the footage. I'd like to replicate the same filtering effect in Resolve but i really cannot understand how to do it because this needs the footage to be translated into float16 format to handle negative values, but looks like Resolve is not capable of doing it.

Any hint? Thanks!
Last edited by Umberto Uderzo on Thu Mar 01, 2018 8:34 am, edited 1 time in total.
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Mads Johansen

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Re: Desharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 5:21 am

Here are a few ideas:

Midtone Detail (MD in tab 2) in Color page sub 0 or adding blur.

There is also a studio only openfx plugin that gives more sharpen controls (can't remember the name, saw it in a sharpen video a while ago, sorry), that should also give that option.

BR
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Hector Berrebi

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Re: Desharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 7:14 am

Mads Johansen wrote:Here are a few ideas:

Midtone Detail (MD in tab 2) in Color page sub 0 or adding blur.

There is also a studio only openfx plugin that gives more sharpen controls (can't remember the name, saw it in a sharpen video a while ago, sorry), that should also give that option.



The OFX sharpening tools (Studio only I think) are excellent because they give control over small/medium/large detail work. there are two (Sharpen and Soften & Sharpen)

Like Mads wrote you can use MD sub zero, if -100 isn't enough.. you can chain a few

In the blur slider, going down (towards 0) sharpens
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Umberto Uderzo

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Re: Desharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 8:33 am

The sharpen OFX plugins looks to me not so effective in trying to remove a sharpness filter. The only "decent" way i found so far is to trying reverse the sharpen filter by some subtract/add of a blurred version of the frame, too badr Resolve doesn't allow this kind of operations because it doesn't handle negative pixel values as Fusion can.

I'll give a spin to the MD, maybe with a edge detect mask.
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Hector Berrebi

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Re: Desharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 10:26 am

Umberto Uderzo wrote:The sharpen OFX plugins looks to me not so effective in trying to remove a sharpness filter. The only "decent" way i found so far is to trying reverse the sharpen filter by some subtract/add of a blurred version of the frame, too badr Resolve doesn't allow this kind of operations because it doesn't handle negative pixel values as Fusion can.

I'll give a spin to the MD, maybe with a edge detect mask.



I must have misread your initial post... my answer was bit off there.. ignore it. sorry :)
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Jed Mitchell

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Re: Reverse sharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 5:30 pm

I haven't tried this specifically, but you might give frequency separation a try and basically reverse the workflow to soften the high frequency detail instead of the low frequency that is commonly done for skin smoothing. Here are two threads I know of discussing ways to build this in Resolve:



http://www.liftgammagain.com/forum/inde ... olve.2983/
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Cary Knoop

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Re: Reverse sharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 6:09 pm

Umberto Uderzo wrote:I'm currently using Fusion to patch a bunch of clips from oversharpening.
I simply subtract a blurred version of the frame from the real frame and use this difference as a patch to fix the oversharpen (partially).

But using Fusion for this simple task is annoying because this means that i need to transcode all the footage. I'd like to replicate the same filtering effect in Resolve but i really cannot understand how to do it because this needs the footage to be translated into float16 format to handle negative values, but looks like Resolve is not capable of doing it.

Any hint? Thanks!

Perhaps I do not understand but Resolve uses single precision 32 bit floats that handle negative values just fine.

By the way I question if your approach will actually improve the quality of the footage. Over-sharpened parts (both halos and ringing artifacts) are very hard to remove because you would have to distinguish between wanted and unwanted high frequency content, which is a very complex operation.
A simple subtracted blur will filter out all high frequency content.

There is a Vapoursynth script which works against halos, but the processing speed is glacial.
https://github.com/IFeelBloated/Vine
Last edited by Cary Knoop on Thu Mar 01, 2018 10:12 pm, edited 1 time in total.
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Jean Claude

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Re: Reverse sharpen footage in Resolve, is it possible?

PostThu Mar 01, 2018 6:43 pm

I have not tested but maybe :
a starting solution is to create a layer node and add in the top node a gaussian blur OFX. Then test on the layer mixer the composite mode. It should be tested. Optionally add a correction node to the output of the layer mixer for a last adjustment. Possibly on the gaussian node, see to adjust the key output from the node key panel.

Not easy... :oops:
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Umberto Uderzo

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Re: Reverse sharpen footage in Resolve, is it possible?

PostSun Mar 04, 2018 9:25 pm

Thanks Jed for the link. I did some testing and Resolve looks like is able to manage negative values, but i got fooled by the fact that in no way i can alter the scope scale to show them, and the layer mixer is still difficult for me to deal with, as i feel the Fusion way more easy to understand. Anyway, i'll do some more experiments to figure out the correct procedure.

Cary, about your question on video quality: i know that each filter is applied to the original footage will degrade more and more the quality, so no, i'm not looking to enhance the quality. What i'm after is to remove the "cheapy" look that the oversharpened Spark footage gives. If i can get my result by slightly degrading it, i can accept the deal.
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Umberto Uderzo

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Re: Reverse sharpen footage in Resolve, is it possible?

PostMon Mar 05, 2018 1:18 pm

Ok, i think i got it.

The graph in the attached screenshot does more or less what i'm expecting.
First, i subtract a sharpened version of the image from the image itself (i decided to work with negated sharpening instead of blurring, as the sharpen ofx plugin gives more freedom).
Then, i add the difference obtained from the previous nodes to the original image, with a 50% key to avoid overblurring.

desharpen.jpg
See zoomed for details.
desharpen.jpg (812.97 KiB) Viewed 305 times


By tuning the sharpen node parameters i can more or less fix the image.

Now i can create a compound node to group all this logic but... is it possible to publish inner node parameters? Or should i need to enter the compound node each time i want to tune it?
Moreover... is it possible to save the compound node for later use in other clips?
Thanks! Umberto
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Micha Clazing

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Re: Reverse sharpen footage in Resolve, is it possible?

PostMon Mar 05, 2018 2:23 pm

If you need to work around the lack of negative values (which surprises me as Resolve internally works in float32 according to Peter Chamberlain), just add 50% grey to your subtraction, and subtract 50% grey again when you add the result back.
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Umberto Uderzo

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Re: Reverse sharpen footage in Resolve, is it possible?

PostTue Mar 06, 2018 6:25 am

Thank you Micha for the hint! Anyway I discovered it was my fault. Resolve is capable of handling negatives.
So far, so good ;)
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Hector Berrebi

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Re: Reverse sharpen footage in Resolve, is it possible?

PostTue Mar 06, 2018 6:38 am

Umberto Uderzo wrote:Now i can create a compound node to group all this logic but... is it possible to publish inner node parameters? Or should i need to enter the compound node each time i want to tune it?
Moreover... is it possible to save the compound node for later use in other clips?
Thanks! Umberto


Nice solution.. the OFX sharpening tools are indeed very good.

1. You need to enter Compound node each time

2. Only way I can think of is by saving a grade, then using Display Node Graph command you can drag the Compound to a node on any clip...
Alternatively you could save a grade containing only the Compound then Append it to other clips, though this might not be always convenient.
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