Noise reduction

[EricBall]

Can anyone explain what the "Still picture" and "Time axis" ranges mean? I understand what they do (spatial & temporal filtering respectively) but I'd like to understand what the 0-100 scale refers to.

I've read that "Range" is the number of pixels in each direction that the current pixel is compared with for spatial filtering. Number of frames would make sense for "Time axis", but 100 frames is a huge amount. Percentage maybe? But a perentage of what?

All the recommendations I've seen simply give values with little or no justification other than empirical and subjective testing.

My current project is to make DVDs of some VHS movies I own. The current picture quality is good, but I'd like to get rid of the RF noise I'm seeing.

[EricBall]

Okay, I have made an intelligent guess for a partial answer to my question.

It occurred to me that the most likely explanation for the 0-100 range would be if it was, in fact, a percentage measurement. Going with that assumption, the most obvious parmeter which would be controlled is a mix between the original pixels and the filtered pixels. So is "Still picture" is set to 45 (and "Time axis" is set to 0), then the encoded pixel will be 45% filtered pixel + 55% original pixel.

Although this would provide some degree of control over the output, it doesn't allow for any fine tuning of the filter itself (other than the "Range" setting). So I have no idea whether the spatial and temporal filters are anything more than lowpass (i.e. averaging) filters.

The hoverhelp ("When erasing time direction noise, prevent grain noise and after image.") for the "High quality mode" checkbox provides a hint as to what it does. My guess is it enables some kind of scene-change detection and performs spatial filtering of the frames before the temporal filtering.