Image Scaling Examples

[Owen]

These images are from a 1080i Mpg2 Pioneer demo.

They where captured via the Print Screen function from my HTPC running Zoom Player Pro in VMR9 full screen exclusive renderless mode on Windows XP. Scaling is via nVidia 8800 hardware.

No editing or manipulation of any kind has been done. The original .bmp images where converted to lossless .png format in ACDSEE to save file size.

The first image is the original 1920x1080 image unaltererd.

This second image has been scaled down 1 percent and a black border inserted by Zoom Player to fill up the 1920x1080 frame.

I also did a 1 pixel downscaled version, but I just cant tell it from the original image and therefore did not post it.

To view these images properly you should download them and use a viewer that allows viewing in original size to avoid rescaling by your software or video card.

Here is the 1 pixel downscaled version as requested. (updated version)

More images, this time in 100% quality .jpg, as some of them where just over the 2M limit of this forum in .png format..

Original image 1920x1080.

There is the same image scaled up 5% and then back down 5% to simulate the effect of scaling for overscan, except that in this case double scaling has occurred to make the images easy to compare. This double scaling will obviously magnify any potential scaling differences.

It is softer then the original, but only just. With motion video you would not pick it.

There is the double scaled image above with a very small amount of sharpening applied, the smallest the ACDSEE image editor will allow. You can get the same effect by turning the sharpness control on your TV up a little. As you can see it is sharper then the original unscaled image.

Now for fun we have the original image scaled down to 1366x768 and then back up to 1920x1080. Again a small amount of sharpening has been applied, but you can do the same on your display by adjusting the sharpening control up a bit.

This one is very interesting, if anything this scaled image is sharper then the original and looses no noticeable detail either, vet it can have no more then 1366x768 visible resolution after the scaling process.

The scaled images in the last set of .jpg images have slightelly higher brightness due to a fault in the ACDSee image editor used, so this needs to be taken into account when comparing.

If people want to get worked up over the tiny differences like these images show, good luck to them, they are a lot more anal then I am.

Personally, I would rather concentrate on things that make a real difference to my viewing experience, but to each his own.

This image is for the benifit of MLXXX, it is downscale 5% by nVidia 8800 hardware.

[bevancoleman]

  Owen said:

These images are from a 1080i Mpg2 Pioneer demo.

They where captured via the Print Screen function from my HTPC running Zoom Player Pro in VMR9 full screen exclusive renderless mode on Windows XP. Scaling is via nVidia 8800 hardware.

Apart from the size I assume? Cause that is quite easy to pick Apart from that it's very, very close. Quite remarkable what a good scaler can do.

You could probably pick the difference better on a fully digital source (i.e. not from film) like modern toons. Of course all video sources will use anti-aliasing, so you are never going to have a single distinct pixel which can be used as a give away. This smoothness (caused by the anti-aliasing) is why movies can be scaled with marginal quality loss.

Games, particularly those without AA, will show up the difference much more. However it's debatiable which will look better, teh scalling will help smoothen out teh aliasing and may actualy look better then the original.

[Mr.Bitey]

The one with the border (scaled) actually looks a bit sharper, there are three little indents on the gold thing just to the left of the bright part of it that look 'clearer' on the scaled (bordered) image than the other one.

Cheers,

Blindy

[Owen]

  bevancoleman said:

Apart from the size I assume? Cause that is quite easy to pick Apart from that it's very, very close. Quite remarkable what a good scaler can do.

You could probably pick the difference better on a fully digital source (i.e. not from film) like modern toons. Of course all video sources will use anti-aliasing, so you are never going to have a single distinct pixel which can be used as a give away. This smoothness (caused by the anti-aliasing) is why movies can be scaled with marginal quality loss.

Games, particularly those without AA, will show up the difference much more. However it's debatiable which will look better, teh scalling will help smoothen out teh aliasing and may actualy look better then the original.

The Pioneer demo is from a 1080i video camera not film, however video from any kind of camera NEVER has 1920x1080 visible resolution even though it often has 1920x1080 pixels. It’ simply a function of how camera (film or digital) capture images, and that is just not understood by most people. 1:1 mapping is just not needed for video content.

There is a lot of misinformation on the net, and people need to understand that PC text - graphics and video have nothing in common.

Scaling is a form of anti aliasing, and can easily improve image quality. By improve I mean make it look more real and less digital.

As for “artefacts” people seem to associate with scaling, I have yet to see any such thing in my 7 years using a HTPC. I have no doubt the scalers in some displays are bad enough to exhibit something that could be called an “artefact”, but I have not spent enough time looking at crappy displays to ever observe such a thing. The normal result of poor scaling is a soft image, that’s all.

[Owen]

  mr.bitey said:

The one with the border (scaled) actually looks a bit sharper, there are three little indents on the gold thing just to the left of the bright part of it that look 'clearer' on the scaled (bordered) image than the other one.

Cheers,

Blindy

The smaller the image the sharper it looks, simple as that.

Sharpness has nothing to do with resolution.

I have downscaling the image to about 50” on my 70” SXRD and it looks much sharper then at full screen, even though it is using only about two thirds of the displays pixels and has therefore definitely lost resolution.

[bevancoleman]

  Owen said:

The Pioneer demo is from a 1080i video camera not film, however video from any kind of camera NEVER has 1920x1080 visible resolution even though it often has 1920x1080 pixels. It’ simply a function of how camera (film or digital) capture images, and that is just not understood by most people. 1:1 mapping is just not needed for video content.

Maybe I should have been more explicit, I mean from any camera, digital or otherwise.

I was thinking of movies that are 100% CG (as in most moden toons) where every pixel is set inderviualy by the renderer. Of course since they will be using AA and since the source frame is at a higher res then 1080p (4k or better) it probably makes no difference.

  Owen said:

Scaling is a form of anti aliasing, and can easily improve image quality. By improve I mean make it look more real and less digital.

Loosly yes, but only sorta. It's true that for a while computers used to do AA by simply rendering to a higher res and then scaling it down to the display res but AA algs are a fair bit more advanced then that now. More importantly AA uses an effective image of many times the size the final image. I.e. 1080p could be sourced from 7,680x4,320 (4x) -> 15,360x8,640 (8x) effective image.

Note I say effective, thats because AA algs tend to be a bit smarter then just rendering a large 8x frame and scaling it down. On some pixels they may not render in higher details at all, and on others they may render at much, much higher res. The choice would be a based on an error margin, if there is no significant difference using 2x AA from the original non-AA pixel then it will not continue to 4x, alternitivily it will keep up'ing the res until there is no significant change.

  Owen said:

As for “artefacts†people seem to associate with scaling, I have yet to see any such thing in my 7 years using a HTPC. I have no doubt the scalers in some displays are bad enough to exhibit something that could be called an “artefactâ€, but I have not spent enough time looking at crappy displays to ever observe such a thing. The normal result of poor scaling is a soft image, that’s all.

BiLinear can generate some interesting effects, but thats because it only scales in on direction (X), on Y it just drops/adds lines

Any modern device should use quad (4 point) scaling at minimum, and hopefully 8-point or better. Of course what devices should and do use...