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I have a reasonably lengthy sequence of PNG's which I rendered while I was away from my machine. To my chagrin, I returned to find that I neglected to enable denoising data at render-time!

I am left with a noisy image sequence (.png) with minor, but noticeable fireflies.

enter image description here

Is it possible to denoise footage that has already been rendered in Blender?

I have tried repairing my footage via inputting the .png sequence into the Blender VSE, and using the denoising data-node in the compositor - but it does not recognize it as a proper render string, or as render data! Thus it will not be accessed via the compositor.

Pierre Ducos
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  • You can run denoising on the images, but the results probably won't be what you expect because the denoiser expects additional data (sample counts and such). This is what you enable with that check box. – Allen Simpson Apr 06 '22 at 15:06

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Don't know about the VSE, but yes, the Denoise node in the Compositor can denoise already rendered image sequences, which means you can import a sequence there, plug it in the Composite output and plug a Denoise node inbetween.

Just note: it doesn't work very well on let's say noisy images from cameras etc. where the noise is maybe even a bit blurred. It has to be the crisp, "one-pixel-noise" from a Blender render to work best.

setup

Before denoising:

noisy

After denoising:

denoised

Gordon Brinkmann
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  • Is the Red node titled "####" an Image Sequence node? (Thank you for your speedy reply!) – Pierre Ducos Apr 06 '22 at 15:12
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    @PierreDucos That's right, it's an Image Sequence node. – Gordon Brinkmann Apr 06 '22 at 15:12
  • I have just one more question - When I render the image sequence, it isn't using our lovely compositing nodes! What do I do to enable the compositor at render time? I am rendering from the VSE. – Pierre Ducos Apr 06 '22 at 15:25
  • I found this thread, for anyone looking to render composite nodes from the VSE! https://blender.stackexchange.com/questions/39396/use-composite-nodes-in-blender-video-sequence-editor – Pierre Ducos Apr 06 '22 at 17:08
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    @PierreDucos Sorry, was a bit late for me to answer, but well, you found a way. I didn't know you needed to render it from the VSE, because just for denoising this wouldn't be necessary. But in the Compositor you should mute or delete the Render Layer so that the scene isn't complerely rendered although you just want the image sequence. Maybe I should add this to the answer. – Gordon Brinkmann Apr 06 '22 at 19:32
  • That would be good! In the end, I created two scenes, enabled rendering from the VSE in BOTH scenes, added my PNG sequence in BOTH scenes, added a "scene" strip in BOTH scenes (each strip referencing the opposite scene - a scene can't reference itself!) and THEN, once the Compositor could be recognized (via the Scene strip in the VSE, which DOES render with composite passes) I rendered - and it worked! (Peachy!) This thread explains this process in further detail: https://blender.stackexchange.com/questions/39396/use-composite-nodes-in-blender-video-sequence-editor – Pierre Ducos Apr 07 '22 at 22:25