These are good questions, thanks for bringing this up! What you're seeing with the deinterlacing sounds like interlace artifacts. In over-simplified terms, interlacing is when a single video frame is composed of two fields (one field is every even line, and the other is all the odd lines) that are recorded one after the other. On standard NTSC sets, these fields are displayed in sequence. On progressive sets (all HDTV sets), they are displayed at the same time. The interlacing is most obvious during fast movements, and therefore when it's displayed on a progressive set, it can cause those blurry artifacts. All HDTV sets have circuitry that converts interlaced video to progressive scan. So in theory, if your final destination for the video is going to be your TV, you can probably opt to not de-interlace it, as your TV will probably do a better job of it than your encoding software will. If you do de-interlace the video when you encode it, the HDTV will just handle it as progressive scan, and you won't take advantage of the de-interlacing magic that it has to offer. The only way to know what works best is to experiment, which it sounds like you have. As far as 2-pass encoding is concerned, it's a matter of file size and not so much quality. It'll make one pass analyzing the video, and logging information about it. Then on the second (or sometimes third) pass, it will actually do the encoding and vary the bitrate depending on the information it logged in it's first pass. So for example, portions of the video that don't need high bitrates (such as all black screens) will be encoded at lower bitrates, thus reducing file size. In some instances this may actually decrease quality, depending on what portions of video the encoder decides requires a low bitrate. It will also take significantly longer to multi-pass encode a video. I suggest really experimenting, because these are things that will have different effects on different sets, and different viewers as well. What I did when I was experimenting for this article, was just rip a single 5 minute chapter off of a DVD, and run that through WinFF at different settings until I found one I liked. A lot of this boils down to personal preference.