1) Could you have forgetten to to specify your codec and compression when trying to apply the filter? I've never heard of a filter boosting your output file size like that. It sounds like Nandub was just outputting uncompressed video. 2) You can always apply filters to completed videos, but what you are actually doing when you do this is decompressing the original file, applying the filter, and then recompressing the output to a new file. 3) As far as "learning" the filters, quite a few of them (resizing, brightness/contrast, sharpen, blur, etc.) are obvious just by openning them and seeing what options they have listed. When you get to the ones that have strange-looking names, it's probably not a tutorial on how to use that filter that you need, but an explanation of what problem that particular filter is trying to solve.