How does an upscaler work?

[hkl8324]

A mean the hardware ones, those upconvert DVD to 720/1080 resolution...
I have a thinking that those upscaler is making something from nothing (DVDs only store 480 information...) Where are those extra line, or details come from? And how do it different from using a software filter (e.g Lanczos3) to resize a 480 viedo to higher resoultion?
And how does those upscaled 720/1080 viedo compare to native 720/1080 (Blu-ray/HD-DVD)???

[foxyshadis]

Upscalers are a mathematical transform, for each output pixel they take a bunch of source pixels, weight them by the nearness to the new pixel's location in the source, and combine them. The specifics define the various kernel transforms, the faster ones have simpler weightings and less pixels.

You can read all about them at wikipedia (http://en.wikipedia.org/wiki/Bicubic_interpolation) or your favorite image processing software's source code.

Hardware is almost always bilinear or point, at most bicubic.

[darkavatar1470]

I have the feeling they won't be much better than doing it by avisynth...
But then again, it's upscaling in real time, which I would probably need 8 cores to do so....

[foxyshadis]

Have you ever watched a video in fullscreen? That's realtime resize. Even an old single-core processor can resize up to 1080p with lanczos while decoding (try it in ffdshow!), though you might need a newer one for using spline or vector-based resize.

[darkavatar1470]

well, I admit there won't be problems upsizing to 1080 by lanczos in real time; but I'd usually throw some other filters down the chain, just plain resizing isn't quite enough.