Feasibility of D-to-Dl scaler using NN/Point for 4k output?

[BONKERS]

With the advent of 4k displays, and re-released retro devices commonly using 720p (1080p still applicable) and scalers to 720p there is the gap of upscaling from that resolution to 4k.
For pixel based games and the desire for a sharp image this presents the problem of the display's built in scaling.
They often do not at all offer the simplest of scaling methods needed for integer scaling, Point/Nearest Neighbor. Resulting in a soft, slightly blurry, or smeared image. Or some combination of any as the display tries to apply interpolation to try and fill in the gaps.
This isn't so bad for offline video content.

However,4k is the perfect target resolution for simple point scaling due to 720p being a simple 3x3(9) scale and 1080p being 2x2(4) scale.
This brings me to my point, the cost(and powerful enough units readily available) for complex FPGA Analog to Digital converters and upsamplers makes creating one for a 4k target output resolution unfeasible.
But, what if there was a simple HDMI/DVI to HDMI/DVI upsampler that only had 2 modes (9x point sample, 4x point sample) simply for pixel quadrupling or pixel nonupling?
The last step to getting a perfectly scaled and sharp image for 4k output while taking the TV's processing out of the mix so it's a non factor.

Would such a device be complex to make or expensive? Would an FPGA be necessary? (I'd assume yes unless you had a dedicated IC). Does such a simple scaling method still run into the same cost/availability/level of power wall that say making a 4k XRGB/OSSC does even though the step of analog to digital conversion and processing to upscale to 720p/1080p is not present?


I really wish PC GPU vendors would finally add this option to their drivers so it would be an easy thing to test and see for any modern PC game. (Instead we are still stuck with crappy box/linear sampling or whatever super basic method they use).
With an emulator it's easier to test and see the effect of this type of thing, at least for retro consoles.
A) Run test with display set to output 720p/1080p, upscale the 240p source with a 3/4x integer scale to that and then let the TV do the rest.
B) Run same test, but with display set to native 4k and upscale 9x integer.


I feel like such a device would be really useful for lower cost retro console re-releases(Lower cost FPGA clones, 720p emulation boxes), adding one last step in the chain of an OSSC/XRGB or playing low resolution HDMI output based consoles on a 4k TV without the potentially blurry or smeared upsampling since few TV manufacturers have the feature. Though it would not help out the cases for the OSSC where the output is limited to 480p. (Perhaps do a simple 16x integer scale and output 1:1 1920 horizontal lines used out of 2160 ?)


Simulated comparisons

2D 240p source
http://www.screenshotcomparison.com/comparison/113265
http://www.screenshotcomparison.com/comparison/113266
3D rendering with HQAA
http://www.screenshotcomparison.com/comparison/113263
http://www.screenshotcomparison.com/comparison/113264
720p 3D rendering with no AA (You end up with ugly filtering similar to that awful HDMI cable that claims to try and do AA, but is just filtering the image aggressively)
http://www.screenshotcomparison.com/comparison/113268
http://www.screenshotcomparison.com/comparison/113269


There is 1 3d rendered examples to show where the TV's internal upsampling may be desirable. With lower resolution 3D rendered content that has extremely high quality Anti-aliasing. (Really only possible on PC. So wouldn't apply to consoles too much, with some exceptions). However for most 7th generation consoles, you are often at 720p or slightly less with often no AA or decent texture filtering. Integer scaling becomes much more desirable here.



Decent idea , or do most people not care about how their TV does the 720p/1080p scaling to 4k, or just that jump from 240p to 720p is good enough scaling to keep it sharp enough?
Scaling on TV sets varies quite a bit, I have 1 set that looks awful, 1 that looks decently fine and another that is in between.

[ZellSF]

720p 3D rendering with no AA (You end up with ugly filtering similar to that awful HDMI cable that claims to try and do AA, but is just filtering the image aggressively)

Source on that? Everything I read and seen about the mCable Gaming Edition indicates it does do post-processing anti-aliasing, then some other undesirable image processing (artificial sharpening, dynamic contrast).

[thebigcheese]

There's a whole Digital Foundry analysis of it, too. That indicates that it does what it purports to do.

On the subject, TBH while it would be nice to have a device to do this, one could also just be more considerate of the TV they purchase. the TCL I just bought is not an expensive 4k TV by any means and, when fed a 5x signal from the OSSC, it produces a very sharp scaled image. Obviously this varies from one TV to the next, but with good scaling options already built in, I suspect there will not be much desire to create a separate product for marginally better results.

[Xer Xian]

But, what if there was a simple HDMI/DVI to HDMI/DVI upsampler that only had 2 modes (9x point sample, 4x point sample) simply for pixel quadrupling or pixel nonupling?

There are such task-specific upscalers already, the HD Fury Linker can sometimes be found for under $100 on ebay, and there's a newer one of which I don't remember the name. I don't know if they use a pixel repetition/nearest neighbor algorithm though. For modern games, this scaling method does not give good result (increases jaggedness).

Thebigcheese has a point though, it seems that FHD to UHD upscaling tends to be acceptable on most TV sets already, which makes a dedicated solution not strictly necessary.