Line Doubler quality

[Rahzel]

I just got a projector with RGB (BNC) inputs that I would like to hook a DVD player up to through a Line doubler. My question is, since the Line doubler only accept S-Video input, will I lose the RGB quality and basically just be the same as S-Video? It doesn't seem to make much sense to have RGB output when the only input is S-video, unless it converts it to RGB.

[Silver]

Yes if you have to convert to S-video at any stage you will lose the advantage that RGB has over S-video. It does seem odd that your unit would have only s-video in and RGB out.

The process of passing a signal through a line doubler will decrease the quality slightly anyway, how much depending on the quality of the line doubler.

[b3atmania]

In Europe most widescreen TVs have a line doubler (we don't have HDTV broadcasts in Europe, instead everything is broadcasted in plain PAL and upscanned by the TV). Quality suffers a lot because of this. Problem with only doubling the lines is that it introduces blurring on fast moving objects. Many line doublers counter this by doing all kinds of digital processing on the image, which is going to be expensive in a standalone unit.

Since DVDs are recorded non-interlaced anyway, your cheapest solution will be to just purchase a DVD player with progressive scan output. Find one with VGA output and you can skip signal transcoding completely. Even if you only get a DVD player with component (Y/Pb/Pr) output, you will have a better source signal than S-video.

If you want to transcode component to RGB I can recommend the Micomsoft XSelect-D4 from personal experience.

[ericball]

The main difference between RGB (and component) and S-video is color bandwidth.  For S-video the color difference signals are bandwidth limitted to 3.57MHz (~455 pixels per line, ~375 pixels onscreen).

A line doubler, on the other hand, attempts to de-interlace the video.  A good line doubler will also perform inverse telecine for video which has been transferred from film.

So RGB will give better color, but a line doubler will give a better image.

Oh, and not all DVDs are non-interlaced.  There are some truely horrid examples of bad image encoding out there which look fine on an interlaced TV but will drive progressive output DVD players nuts.