Quote:
Originally Posted by Mentar
And to complete the circle of my argument: Does that mean that you can take any source and just use the same technique to create MHD out of a SD source? In my opinion, no - you can apply the same technique, but the quality gain depends on the detail grade of the source. If the source itself has been created HD, the MHD trick works, because there are enough details for the upscale to trigger, and to avoid making the upscale look like a mere oil painting. If the source itself is merely conventional SD quality, it does not.
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I don't get why you keep feeding the trolls by redefining HD. It's irrelevant whether an SD source was created by HD downscale, a scanner, or MS Paint! The level of detail counts. And the maximum level of detail is probably higher when people aim for HD, thus your correlation. But it is definitely possible to get a better upscale from an SD source than from a HD->SD downscale due to resolution interference on downscaling. In reality, of course you are right - the HD downscales look better because the ones creating only for SD don't really care about image quality anyways.
As to all these image "tests" so many people did: To revert an upscale, you have to use the exact same method backwards the upscaler used. I think this is what most people in this thread didn't get. The exact method of the original upscaling the station did is very important if you try to proove anything by reproducing it. This is why results differ. You have an upscaled SD source. People who hit the mark by choosing the method to re-downscale it get better results than others.
Let me try to make rules out of this:
- The maximum possible quality is defined by the minimum resolution used at some point in the process. Any results below the maximum are meaningless, as screwing up is easy.
- Most image processing is NOT bijective and thus IRREVERSIBLE. Even if it theoretically is reversible, in reality it's usually not because of differing methods used.
So it's pretty simple really: If you get a decent image, do not mess with it if possible. If you get it messed up, try to carefully make it bearable again, damaging as little information as possible.
Eclipse did the RIGHT thing NOT resizing the image again. Blame the ones who created the original source if you don't like the quality!
one more thing: As far as I'm concerned, all quality losses discussed here are minor compared to the first HD->SD downscale. I must completely disagree with Mentar's comparison of HD->SD->HD scaling with HD->HD->HD encode. The difference in detail is
massive, proving the theoretical numbers. See Gundam 00 or the likes. I've watched the opening so often now - it's just beautiful. Unlike any TV rip I've seen before. But probably it's just the first one I saw that was neither high-compression reencoded before the final encode nor ever resized to SD.