How does upconversion work?

[Jaguar007]

A question about upconverting? How does a machine upconvert a SD DVD (420 or something like that) to 1080? I know upconverting is not as good as true 1080, but how do you get something from nothing?

Basically how does upconverting work?

[HeavyHitter]

As I understand it, the scaling chip performs an algorithm which does an extrapolation of SD DVD (720X480) to HD (1920X1080 in this case). In other words, it creates "fake" pixel information based on the source material.

[Smackos]

As the post states above.. basically the upscaling chip/software fills the correct pixels and approximates what the ones missing from the new resolution SHOULD be.. but like you even said yourself in your first post-you can't just create something from nothing and since there's no real information there it cannot hope to match the clarity or detail that a true 1080p source material like blu-ray gives.

[dialog_gvf]

Originally Posted by Jaguar007

A question about upconverting? How does a machine upconvert a SD DVD (420 or something like that) to 1080? I know upconverting is not as good as true 1080, but how do you get something from nothing?

Basically how does upconverting work?

It's complicated in practice, but it's easy to give a simple example. Say you have the following pixel values:

120 124 128 130

Now, if you wanted to double your resolution, you could create (interpolate) the intermediate values:

120 122 124 126 128 129 130 ???

The real thing will need to deal with RGB or YUV in two or three (comparing frames) dimensions, and do edge detection to make sure it doesn't fuzz the edges, but it gives you the basic idea.

Gary

[welwynnick]

Everyone usually forgets what is probably the most important process with "up-conversion".

De-interlacing.

SD video is 480i (or 576i), which is interlaced. What we usually want is 1080p, which is propressive. The most important process is de-interlacing; the conversion of interlaced to progressive video. That's complicated and difficult to get right. Get it wrong, and the softening or artifacts are simply magnified up to high def by subsequent scaling processes . Here is a very good description of whats involved if anyone is interested. It's a sales pitch for Silicon Optix, but there's no better explanation, except maybe some of the technical articles on Secrets of Home Theater and HiFi.

Scaling is a walk in the park compared with de-interlacing. It's a straightforward mechanical process that can be done by any amount of cheap silicon (though most folks reckon Lumagen still do it best). Scaling in itself doesn't buy you very much image quality. All displays will do it anyway, and won't have any pixel-matching problems like you have with most digital interfaces.

There are other processes to consider, like noise reduction, frame rate conversion, telecine and image enhancement, but they are for another time.

regards, Nick