How do I go about filtering out "video noise" without making the low-light portions of videos look "blocky"?
http://forum.videohelp.com/threads/235245-Avisynth-denoise-filters-comparison-%28WARNING-56K-MODEM!!%29
that thread has some comparison shots between different denoise filters of AVIsynth. Maybe you will get some tips from those images.
Sorry, but that thread doesn't answer my question about filtering out "video noise" without making the low-light portions of videos look "blocky"
You don't gonna like what you are reading next.
It is all a trial by error. Take a small test sample, and try applying the filter(s) and change one parameter at a time. See if the situation improves or get worse. If the video is already compressed, most likely you never get the result you want. Agent_007 is proposing to use Avisynth. Applying filters always has the risk of degrading the picture. I never use these, don't have the time or patience to do this.
Try other filter(s) our combination.
If you want more information: Avidemux noise filter (http://www.google.com/#sclient=psy-ab&hl=en&site=&source=hp&q=AND+avidemux+AND+noise+AND+filter&oq=AND+avidemux+AND+noise+AND+filter&aq=f&aqi=&aql=&gs_l=hp.3...6057l6057l0l7019l1l1l0l0l0l0l58l58l1l1l0.frgbld.&pbx=1&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=c2bfba639d23eb7a&biw=1362&bih=873)
Check in avidemux Preferences: Video: Default Postprocessing: Unmark the 3 options and see if it improves. If it does not: lower strength.
Document every step on paper what you are doing. when you get the result you want: make new paper with steps you did make and archive it very well.
Perhaps other users will share there secrets on filter usage?