Today I found Defly again on my harddisk.
Quotes from Konstantins Homepage.
“Even though Octane has a built-in noise reduction (that seems to be based on principle explained here)
it’s sometimes useful to be able to do filtering independently from rendering,
to avoid lost details during animation or re-rendering animation,”
“Konstantins Visnevskis, 04-06-14 17:11:
… Anyhow, I’m wondering, why something like this still is not implemented in Blender.
The principle is really simple.”
Okay, as a Non-Programmer I don’t think it’s really simple, but
maybe a developer can contact Konstantins.