I'm using virtualdub 1.10.5. I loaded in my 1080 video, added the neat video filter and done remving the grains with it. And back in the preview window, everything is normally as it shows input and output panes. However, after about 6 seeks in the time line, the output pane start showing grains again, not as much as the original.
If I open the filter dialog box and click ok, the output pane preview correctly again.
And if I open the filter dialog box and click cancel, it will add more grain to the output pane. Repeating this will add even more grains, eventually making it identical to the input.
Ok I think I know where the problem came from. It's the adaptive filtration option that was causing this. When I turn it off, everything work as normal.
Well I don't really know what adaptive filtration do, I just leave it on.
And after testing a few more videos, looks like the problem only exist in my dragon ball z level set blu ray clips, where they have huge amount of grains.
Please check the description of that option in the user guide to make sure you use it correctly. I do not recommend to just enable it everywhere, that is not right. Which is why it is off by default.