4(b). D925 - s-video - BT878 (after AviSynth processing)

This shows the result of a simple levels tweak in AviSynth with a 5-capture average (compare to the original No. 4).

The black level was originally too high, the levels tweak has brought it down to where it should be.

Multiple capture averaging is a technique for reducing noise that can, in theory, be totally non-destructive. All other denoising methods can lead to a loss of detail, either spatial (smoothed textures) or temporal (blurred motion). Even though the latest motion compensated algorithms can help, such denoisers can never be completely non-destructive.

Yes noise levels are reduced (notably in the chroma) and there is no loss of detail, but what impressed me about using this method is the virtual elimination of dot crawl artefacts at colour boundaries. You could argue that you don't actually need a 3D comb filter as this method produces results that are just as good.