How to reduce temporal flickering after frame-by-frame restoration?

[lastchance22]

Hello,
I am working on an anime remaster/upscale from a DVD source, and I am having a temporal consistency issue after processing the frames.
The video was processed frame by frame, then rebuilt into a video sequence. The result looks good visually, but during playback I notice a slight temporal flickering/instability: some details, textures and fine lines slightly change from one frame to another, which creates a subtle "shaking" or "breathing" effect.
It is not a typical compression issue. The problem seems to come from small variations between consecutive frames after the restoration process.
I already tried temporal denoising (TemporalDegrain), which helps reduce the effect, but I am looking for a more effective solution that could preserve details while improving temporal stability.
Are there any recommended filters, workflows or techniques to reduce this kind of temporal flickering after frame-by-frame restoration/upscaling?
I can provide a short sample clip if needed.
Thanks for your help.

sample: http://titant.free.fr/tmp/Sampleraw.zip

[Selur]

side note: since the filtering seems to be rather strong, instead of using a single image model using BasicVSR++ might have been a good idea
for your clip try Filtering->Vapoursynth->Frame->Stabilize and increase the strength, (maybe even enable 'Denoise') that should help at least with small flickering.
Maybe even apply it twice in a row.
https://www.mediafire.com/file/711qyq1kn...2.mp4/file
https://www.mediafire.com/file/5nuakf55i...3.mp4/file
Such issues are way easier to deal with at the original resolution before upscaling.

Cu Selur

[lastchance22]

Thanks for the advice! By any chance, do you know if there's a way to refine the linework to make the result look a bit more like a remaster?

[Selur]

Not really,.. but here are a few thoughts about that:
You can use Filtering->Vapoursynth->Sharpen->aWarpsharp2 or Filtering->Line->Misc->Thin to thin the lines a bit, but that probably will not help much.
Alternatively maybe downscale before resizing and use something like Anime4KCPP/RealESRGAN might help.
Maybe someone over in the Discord Channel of https://openmodeldb.info/ even has a special model for filtering DB.
Downscaling by 2.51 and Upscaling using 4x_UltraSharp:

Starting from the DVDs would probably give you better results.
Alternatively using something like seedvr2 through ComfyUI might also work. (wild speculation)

Cu Selur