thecoalman - 4:42 am on Jun 22, 2013 (gmt 0)
The ideal format for archiving is the most original source, it's all downhill from there.
I should add that is not absolutely true, if for example you're capturing VHS using a DV converter using some very light filtering on the capture can do wonders. This will also greatly improve your output for compressed formats like MPEG2 because the encoder doesn't have to allocate as much bitrate to the noise.
Virtualdub is a great tool for processing video and has numerous filters. There is lot of tricks you can do with this like creating sequential images and then use your favorite image editor to batch process the frames with a noise filter. One thing to note if you're going to explore this is be sure to read up on how to unfold interlaced frames before processing. then refold them...