[vdr] 1:1 pixel mapping - a waste of time?

Ville Aakko ville.aakko at gmail.com
Mon Jan 5 23:52:10 CET 2009


2009/1/6 Scott <scott at waye.co.uk>:
> As Im just starting to get vdr working, I was wondering if 1:1 pixel mapping
> between the video card (nvidia onboard HDMI output) and my flat panel
> (Samsung plasma) is a waste of time.  When looking at a "computer" generated
> image like the desktop, its going to make a difference, but with broadcast
> material (SD mostly), I imagine that the material is scaled anyway to fit
> the resolution of the panel (which in my case I think is 1024x720, but that
> has a bit of overscan).  So it wont be 1:1 anyway, or am I wrong here?    I
> know this is a bit off topic, but there seems to be a fair bit of experience
> here.

I'd say it's not a waste of time.

In general, it is a good idea to avoid any (unnecessary) processing.
If you do not setup your video card to your display 1:1 to your
panel's native resolution, you're most likely going to get an extra
scaling of the video image (which is totally unnecessary and degrades
the image).

For example, if your panel is 1024 x 720, and your video card is setup
for 1280 x 768, then you'd end up first scanling a PAL/NTSC/whatever
video to the 1280 x 768 and then your panel is going to scale it to
1024 x 720. You'd get better results if you'll scale straight to the
native resolution of the panel via the video card, or set the video
card to the native resolution of the source material and let the panel
do all the scaling.

I don't know how to do the latter, and even if it is possible in all
cases. In my setup, I have set up my video card to 1:1 to the panel I
have (fullHD), since I have material in several different resolutions,
and also use a desktop on my VDR box.It's more hassle free this way,
if I would have chosen the latter case, then I would be constantly
chancing resolution. It should be quite easy to setup 1:1 pixel
mapping with any reasonably new display, video card and X.org, since
the X.org uses EDID information quite well these days. Though, in
practice, the DVB broadcasts are so much degraded by the mpeg
compressing process at least here where I live, so it doesn't actually
matter that much how you do the scaling ;=).

YMMV. In any case, a (single) scaling process gives better results
than 2 x a scaling process.

-- 
Ville Aakko - ville.aakko at gmail.com



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