Digital noise reduction - a warning

[Quasipal]

Just thought I would share as I have just wasted 2 hours re-doing a VHS to DVD dub. To cut to it, some scenes had tiny falling snowflakes behind the actors. These flakes helped set a mood and were important to the feel of the story. As these tiny white grains were random and only on the limit of VHS resolution the JVC and Panasonic VCR's with DNR lost around 90% of the snow falling, making the film have a different feel. I have done them again using my Panasoniv NV-HS800, with AI turned on and this lost none of the snow (but now I have some grain).

So, just be careful that when you select DNR on your VCR or on the computer, that you are not losing anything that is mixed in with the video grain.

[chowmein]

You would have better control over this sort of thing using an avisynth denoiser, eg MCTemporalDenoise.

[lordsmurf]

Something of that nature is likely to be re-lost, due to the nature of MPEG compression.
This is one of the few areas that HD becomes very useful.
And this is when I'd look to creating HD upscaled H.264 Blu-ray versions.

[Lodovico]

You would have better control over this sort of thing using an avisynth denoiser, eg MCTemporalDenoise.

Or use NeatVideo in VirtualDub, tuned to a patch of the VHS grain without snowflakes. If the noise reduction is still too strong during the snowflake scenes, you can reduce the effect of the filter or turn it off altogether in those segments by Blending it with the Curve Editor.

I've also had to re-do a few captures because the VCR DNR button had taken out too much. I get better results now by doing the noise reduction in software. (This is when capturing to lossless avi - if you're using a DVD recorder, then some pre-capture DNR is advisable to improve compressibility.)

[davexnet]

Interesting post. I wonder how analog capture cards (with their own flavor of DNR) would handle this ?