Special deinterlacing method for not-really-interlaced video

[mark_k]

This is a suggestion for a new deinterlacing method, primarily useful for "interlaced" source video that isn't really interlaced. I'd better explain what I mean by that...

Almost all older home computers and game consoles, up to and including the PlayStation 1 and Saturn, output non-interlaced video. That's sometimes referred to as "240p", or "288p" for PAL. When you capture video from a system which outputs 240p, e.g. with a USB video capture device, the computer sees a normal interlaced video signal. That's not a particular problem for e.g. saving your gameplay to an AVI file or whatever. But for playback, normal deinterlacing methods are not optimal.

In the "interlaced" video file which you capture, instead of odd and even fields whose lines are interleaved, the video sequence actually consists of ~60 progressive 720x240-pixel frames per second.

Normal weave deinterlacing isn't ideal because it introduces artifacts, with two successive frames being visible at the same time. Normal bob/doubling type deinterlacing can result in vertical "jittering", because it assumes the vertical position of successive fields differs. That's not the case with this not-really-interlaced video.

To properly display such video, each field (actually, frame) could be simply doubled in height. That could be simple pixel-doubling or increasing height by adding an extra line in between each pair, which would be a blend of the two adjacent lines. A further option would be to make the extra lines a brightness-reduced blend of the adjacent lines, which would give a nice CRT-like "scanline" effect.

Having that ability would allow gameplay footage to be played back at its native non-interlaced 50/60fps. And if VLC can output this "de-interlaced" footage, the user then has a nice 480p video for upload to YouTube etc.