Temporal Noise Reduction : Ghost images from previous clip

Hi everybody!
When using Temporal Noise reduction on a single clip (which has been cut through an edl or manually), there is a ghost image, coming from the previous clip on the timeline, which appears in the first frame of the clip where the noise reduction is applied. (same for the last frame)
No way to have a workaround?
Neat Video Noise Reduction doesn't have this issue even if it uses also Temporal noise reduction.
Maybe this could be fixed in a future update by BlackMagic?
Many thanks
Luca

Never saw that behavior myself. How may frames you using? (I typically use 3.)

Does the problematic clip have handles for the TNR algorithm to use?

There are also settings for Motion Estimation that you could play with. Or you could set some keyframes to remove TNR from the 1st and last frame, maybe hit those frames a bit harder with spatial NR.

Although you have a cut in the timeline, I suspect the clip you're degraining has a scene change one frame before your first visible frame. That's where the ghost image is coming from.

Good thought, Igor.

I have experienced this many times with the scene-detect/EDL workflow. The workaround I've found is:

1. Option-drag a copy of the clip in question up to the next track on the timeline
2. Remove your grade from the copy
3. Create an edit on the second frame of the copy and copy that first frame back a frame (basically, duplicate the first frame)
4. Go to the Deliver page and export the copy (with duplicated first frame) in some high-quality codec
5. Edit the new clip back into your timeline (it now has a handle at the beginning)

I feel like Resolve should detect when the frame it's trying to use is from a different shot (in knows how to detect cuts, after all), but for now, this is what I do.

Can you get them to send you the project with one-second handles on each clip? That should cover this issue with TNR, and allow applying transitions or slipping a cut a frame or two.

Hi everybody,
sorry I was absent for a while.
Indeed no in this case I cannot change the workflow of the production.
The only solution was to put keyframes at the beginning and at the end of each clip. But this is a lot of work as I usually have hundreds of clip to denoise...

Juts to be more clear about the issue if it was not clear for someone.
Take a movie that need to be color graded.
Make an export .mov and an edl.
Import a timeline in Resolve with the cuts from the edl.
Then apply the TNR. For ex with 3 nodes
You don't see the issue all the time, you can see the issue particularly when there is a big change in luma between two shots. Ex first shot clear second shot dark.

Another way to overcome the issue is to use Scene cut detection and then Add cuts to media pool. This will add in the bin all the cuts as separate clips.
(Unfortunately I cannot change anything in their workflow for this production)

By the way Neat Video use also Temporal Noise reduction but does not have this issue. So an upgrade from Blackmagic would be welcome.

I cannot change the workflow of the production.

Why not? The one you're using is...odd.

In DaVinci Resolve, the decision to export clips with handles is just a checkbox. I imagine that the major NLEs have this capability. How is asking them to reexport but with handles this time a change to their workflow?

I cannot ask to change the workflow because they use it since years and they don't want to change for me just arrived...

There is no handles in this case. It's an AAF from Avid but taken from a single file.
It means they have a timeline on Avid with a single video cut in many parts. Don't ask me why.

But my point is that Resolve could change the way to evaluate the noise, taking into account that there is a cut on the timeline so it shoudn't go to look on a previous clip, this would be much easier...

Are you using a timeline based TNR node or clip based nodes? Clip based should not see frames from adjacent clips. If timeline based node, that’s probably the problem.

It's not a timeline based node, it's a clip node.
IT see it as a unique file because if you look in the media pool it's a unique file but it is cut ine the timeline in many clips.

if I understood correctly your issue, this is a common issue for either shots that have a first frame of slate or for already cut reels of a feature for restoration that you cut with an edl. also for already conformed pieces that you cut with an edl.

even if you cut a shot, there is always a frame of hidden tail that is the outgoing shot (or the incoming) and the TNR will look into it and use it. being a completely different image, the TNR will do a garble of it.

The recommendation to BM was to introduce a checkbox where the TNR ONLY use the frames that are visible (in the cut) for computation. that was a couple of years back and few threads deep in the software suggestions.

there are very few workarounds unfortunately....

The recommendation to BM was to introduce a checkbox where the TNR ONLY use the frames that are visible (in the cut) for computation. that was a couple of years back and few threads deep in the software suggestions.

Thanks for your message, I hadn't found previous threads about it.
It's a shame blackmagic didn't hear it. Moreover I believe a lot of people use it and never realize that there are ghost images. Quite often you don't see it in play unless you stop at that frame.

I'm late to this discussion, but here is what I found out just now, after having the same issue in Resolve 17:

I was able to get rid of the ghost images by setting the Motion Range in the Temporal NR panel to Large (Medium seems to be the default).

In my case the clips all came from one telecine file and had therefore no handles. (or rather. the "handle" was the previous image)

Hope this helps.

The recommendation to BM was to introduce a checkbox where the TNR ONLY use the frames that are visible (in the cut) for computation (exclude tails). that was a couple of years back and few threads deep in the software suggestions.

this is still a HUGE problem when working on restoration projects: you have a ringle reel with cuts and the temporal noise reducer ALWAYS generate artifacts at the first and last frame.

super annoying.

Would NeatVideo handle this?

The recommendation to BM was to introduce a checkbox where the TNR ONLY use the frames that are visible (in the cut) for computation (exclude tails). that was a couple of years back and few threads deep in the software suggestions.

this is still a HUGE problem when working on restoration projects: you have a ringle reel with cuts and the temporal noise reducer ALWAYS generate artifacts at the first and last frame.

super annoying.

It's the same with using Optical Flow for speed changes, and has the same workaround. Once I have cuts added, I render the whole timeline as individual clips, adding a prefix. If possible I use the same codec so I can bypass the re-encode to make things quicker.

With these clips added to the media pool, just drag and drop onto the timeline, since they will be in order.

Not ideal of course, especially when dealing with long form as it will double the required space. But if you only use TNR on a few shots then those could be singled out for creating as separate clips.

* actually for long form it would be better to export an EDL and load that into Scene Cut Detection as mentioned earlier in the thread, not something I've tried though

It’s a lot of workarounds… and space….

Would NeatVideo handle this?

Yes, there are zero artifacts with a scene cut workflow with Neat Video, and I'm not sure of the reasons why except that it's completely different software. My guess is that they're looking ahead at least 4-5 frames and can interpolate the difference between a scene cut and an ongoing shot, and that works for both their versions of TNR and SNR.

Note the initial cost of Neat is $349 (even more expensive than Resolve itself), but ours has paid for itself many times. It's also very slow compared to Resolve's NR -- I think ours renders at about 12fps as of version 5.5 -- but it's a lot better than it was a few years ago, when Neat was more like 2fps. Neat has salvaged a few jobs for us where it started out "almost unreleasable" and improved to to "barely acceptable," which thrilled the client.

There''s a few tips and secrets with Neat, and I believe @Jason Bowdach has covered some of them in a past tutorial over on MixingLight.com.

There's a special version for Resolve only, which is cheaper.
And it's pretty fast with M1

Guys, I’m not asking for a different software solution: we have literally close to a hundreads of machines, i cannot ask to install “this magical plugin that solve the problem until it kill teh realtime to a crawl and the client leave in pain”.

Resolve has a noise reducer tool, just add a functionality to it to DO NOT look at tails when a cut is there.

But isn't it always like this? You can either ask the manufacturer with a 'pretty please' and wait for it or find an alternative if you need it now?
And then, for so many machines it should be possible to strike a good deal with Vlad or get floating licenses.

Guys, I’m not asking for a different software solution: we have literally close to a hundreads of machines, i cannot ask to install “this magical plugin that solve the problem until it kill teh realtime to a crawl and the client leave in pain”. Resolve has a noise reducer tool, just add a functionality to it to DO NOT look at tails when a cut is there.

I think the issue is that Blackmagic Design is very busy fixing bugs and adding new features, so my guess is they rarely have the time to go back and fix a legacy feature like Noise Reduction. I can think of a long list of feature suggestions and improvements that have yet to be taken care of going back many years (at least to Resolve 12). As it is, it's amazing to me how much gets accomplished in each release.

Warner Bros. MPI is actually using Neat Video with their latest film restoration projects (including the acclaimed Godfather 4K Dolby Vision release this year), and they have some interesting ways of using the tool. Part of their secret is to mix one layer of a noise-reduced render with an original-clip video layer -- sometime as a composite, sometimes as a wipe, sometimes as a blend. It's great when you have the time to to it that way, allowing you to noise-reduce only shadows, only highlights, Y-only, or chroma-only, or just specific colors.

But isn't it always like this? You can either ask the manufacturer with a 'pretty please' and wait for it or find an alternative if you need it now? And then, for so many machines it should be possible to strike a good deal with Vlad or get floating licenses.

I think Walter's point is that if you work for a large facility (as he does), it's tough to convince them to run out and pay for X seats of additional software to do a specific function. What used to happen to us at Technicolor is we'd have one room with certain options and another room with other options, but you could never get both of them at simultaneously for a scheduled session. I think there are ways to juggle problems like this logistically -- for example, have a render workstation in the machine room that has all the plug-in(s) -- but every facility is different. I don't know if Neat offers site licenses or not.

In the audio mixing business, you could have something like an iLock and keep all the authorizations for a Pro Tools system on that, and then plug-in this device on any other system you needed temporarily just to open up those functions. Not so simple with video.

I think the issue is that Blackmagic Design is very busy fixing bugs and adding new features, so my guess is they rarely have the time to go back and fix a legacy feature like Noise Reduction. I can think of a long list of feature suggestions and improvements that have yet to be taken care of going back many years (at least to Resolve 12). As it is, it's amazing to me how much gets accomplished in each release.

It's the same with most softwares, established bugs get a lot less action than bugs in new features because users are already used to them and fixing might break workarounds, introduce new bugs etc. Established Resolve users are also not generating any income whatsoever due to licensing logic so fixing old bugs has zero sales value.