Speeding Up Shots -Choppy Render vs Artifacts in Render

Relatively new to Resolve - using since Oct 2020. I've been searching and reading this forum a lot - tons of good info here. I also have been utilizing the manual and videos on their website as well. Hard to believe this product is free, but I get why they are doing it.

Running 16.2.7.010 on a MBP.

I've produced four videos and have bene happy with them so far.

Working on a new one now and running into an artifact issue with Optical Flow.

I've sped up clips along the way and discovered that I needed to adjust frame interpolation to "smooth" out the sped up clips. The sped up video would appear somewhat choppy in certain sections with Nearest.

I've used Optical flow with no real concerns up until this one short section in a video I am working on now.

I did a fly over of this house and there are a few frames that have some funky artifacts. In the first shot, I've circled the area to show what the shot looks like correctly without the artifacts:

Shot1.jpg (201.22 KiB) Viewed 1038 times

There are a few frames where garage windows and a section of roofing with metal flashing that have artifacts produced from optical flow.

Shot2-2.jpg (119.21 KiB) Viewed 1038 times

I tried all three frame interpolation methods as well as adjusting the motion estimation mode and motion range.

Nearest/Frame blend eliminate the artifacts highlighted above, but the video is a bit choppy.

Is there a trick/tip anyone has?

Is there a different way to tackle this problem?

Thanks for the help in advance.

Cheers.

Thread bump.

Any tips/suggestions or another way to tackle this artifact issue?

I discovered on the cut page there is additional effect (Ghosting speed processing button) via the manual, but as far as I can tell that is the only way to access the tool - in that one spot.

Unfortunately, there appears to be a bug in DR outlined in this thread:

https://forum.blackmagicdesign.com/viewtopic.php?f=21&t=113053

Any other way to access "Ghosting" effect as outlined in the manual on page 468?

A keyword search of the manual indicates there isn't, but I figured I would ask just in case. Stuck at this point on this clip.

Cheers,
Matt

Optical Flow Is not a magic bullet solution for all retiming scenarios. The accuracy depends on the type of motion in the frame, so it’s hard to gauge what your specific issue may be, since you only posted stills.

If the shot does not have reliably predictable pixel movement from frame to frame, or has a lot of “cross motion” of various elements (eg a light pole in the foreground moving at a different speed and plane from whatever is directly behind it) then you’ll find that most optical flow algorithms will cause clumpy, tearing artifacts. Resolve does not give you much flexibility in tweaking the algorithms, unlike a dedicated tool like Twixtor, so there’s only so much you can do to deal with issues like that.

One method is to selectively composite together different retiming methods, so that the problematic areas use Frame Blend instead of optical flow. You can sometimes get away with quick and dirty solutions like that, if the majority of the frame looks good when using optical flow retiming.

Optical Flow Is not a magic bullet solution for all retiming scenarios. The accuracy depends on the type of motion in the frame, so it’s hard to gauge what your specific issue may be, since you only posted stills.

Yeah, I figured that out over several videos. Overall it's worked quite well when speeding up clips - this was the first time I've really had an issue. Nearest and frame blend just end up way too choppy. I am working on filming these shots "quicker" so I don't have to speed up the flow in post.

unlike a dedicated tool like Twixtor, so there’s only so much you can do to deal with issues like that.

Yesterday I spent some time looking for solutions outside of Resolve. I ran across Twixtor. Since this is such a tiny small section and the only video I have had an issue with thus far, I don't feel the need to invest in Twixtor as of yet. Perhaps down the road. Better yet, improve my filming speed.

One method is to selectively composite together different retiming methods, so that the problematic areas use Frame Blend instead of optical flow.

I considered this as well. As mentioned above, the resulting choppiness with passing roof in the clip are far worse than the issue above. I've found the optimal settings in Optical Flow that produce the least amount artifacts in the roof and garage windows.

I currently have a "low tech" work around. I needed to add information (titles) to the clip in this section so I timed one of those "titles" with the appearance of the artifacts (it occurs in the highlighted area as it reaches the bottom edge) and placed it in the clouds/sky at the top just before the artifact appears. Not a solution, but the best I can do at this point.

I was hoping to find a potential work around from someone.

I much appreciate the post.

Cheers,
Matt

If it's only a short section, did you try Speed Warp (only available on a per clip base)?