Blackmagic Forum

Hello everyone,

I'm experiencing a severe issue when using Optical Flow Retiming in DaVinci Resolve 20 Beta 2 and Beta 3 on Windows 11 with my AMD Radeon RX 7900 GRE.

As soon as Optical Flow is enabled—especially in combination with Retime—massive image distortions and glitches appear, making the footage unusable. The issue becomes particularly severe when using object tracking in Fusion and then applying slow motion with Optical Flow via Retime.

The issue is fully reproducible and occurs across different projects and clips. The problem is significantly worse when I use keyframe curves or uneven speed values like 26 instead of 25.

Some important notes:

I cannot reliably comment on Beta 1, as I hadn’t used Optical Flow with Retime in that version.

In DaVinci Resolve 19.1.4 and earlier versions, I had no such issues using the exact same hardware and settings.


I suspect this might be a compatibility issue between the current Optical Flow implementation and AMD GPUs—specifically the RX 7900 series.

I'd also be curious to know if other AMD users (especially with 7900 cards) are experiencing similar problems.

Thanks and best regards,

Hello everyone,

I’ve now tested this issue with two different GPUs and was able to reproduce the bug on both:

• AMD Radeon RX 7900 GRE
• NVIDIA RTX 5080

The issue occurs regardless of the graphics card used.

As soon as Optical Flow is enabled in combination with tracking in Fusion, severe image distortions occur – the footage becomes unusable.

Some important notes:

• Optical Flow alone works fine.
  
• Tracking without Optical Flow also works without issues.
  
• Only the combination of Tracking + Optical Flow causes major visual artifacts – especially when using non-integer speed values (e.g., 26% instead of 25%). With even values like 50% or 75%, the issue is less frequent or doesn't occur.
  
• The problem exists in Beta 2, Beta 3, and Beta 4.
  
• In DaVinci Resolve 19.1.4, this issue did not exist with the same hardware and settings.

I suspect a fundamental issue in the new Optical Flow implementation, which is not GPU-specific.

I’ve included a share link with a sample video showing the issue as well as the original clip.
https://www.dropbox.com/scl/fo/p9wq5t1t ... tknog&dl=0

If any developer is reading: I’m happy to provide project files and diagnostic logs if needed.

I’d be very interested to hear if other users can reproduce this behavior.

Thanks and best regards,
Faruk

We're gonna need a DRP, because just tracking the flower doesn't change the footage.

Hi Mads,

thank you for your response.

To clarify: yes, Optical Flow is being applied after tracking – I apologize for not stating this explicitly in my initial post.

I’ve now added a .drp project file to the same folder, along with an additional original clip. With this particular media file, exporting is not possible without triggering an error, even when no effects are applied beyond the tracking and retiming.
https://www.dropbox.com/scl/fo/p9wq5t1t ... tknog&dl=0

Please let me know if any further diagnostic material is needed.

Best regards,
Faruk

I think I have the solution as to why:
As seen on page 3177 (Overall image processing) in the manual, Fusion is before timeline processing. Since Speed Change is a timeline processing, Fusion has no idea that there's extra frames, and Davinci then inserts black frames.

I don't have time to test today, but I see three options: 1) Stabilize the footage in Fusion, render it out at 100% speed in your intermediate format of choice, then do the speed changes.
2) the reverse: Do the speed changes, render, then Fusion stabilize
3) Stabilize in Color page. Since the Speed change is a Timeline processing, Color does have access to the extra frames and it can be done in one go.

Fusion does not need to know there is any retime going on. It produces frames that for all intents and purposes from Fu perspective are final (like in rendered video). These frames should then be retimed in timeline processing, again regardless of the frames source. There is no logic by which it should start inserting black frames "by design". If timeline env makes an unfillable request to Fusion or valid request fails to render a frame in Fu it is a bug.

Hello,

Mads Johansen wrote:3) Stabilize in Color page. Since the Speed change is a Timeline processing, Color does have access to the extra frames and it can be done in one go.

That does indeed seem to be the cause.
I tested it earlier – and basically, it works if you track an object in the Color tab and then apply stabilization.

In my real-world projects, I often stabilize signs or labeled objects in moving footage to enhance readability and create a distinct visual effect. This allows me to deliberately draw the viewer’s attention to specific elements in the image.

In Resolve 19, this workflow worked exactly as I intended – possibly even in version 18, though I’m not entirely sure. That’s why I’m surprised the behavior has changed now.

So far, I’ve preferred doing this in Fusion, since the Transform node gives me more direct control over the visible framing.

I’ll have to test whether this kind of approach can be replicated in the Color tab.
I'll also try prerendering, even though it’s not my preferred workflow, as I want to avoid unnecessarily increasing the number of project assets.

Hendrik Proosa wrote: If timeline env makes an unfillable request to Fusion or valid request fails to render a frame in Fu it is a bug.

I agree with Hendrik, this definitely wasn’t the case before and I believe it really is a bug.

The issue is still present, even with the official release version, which in my opinion was published far too early.

What’s the best way to directly address this to the developers? Are they monitoring this forum, or is there a way to open a proper support ticket?