Would perhaps be a better fit for a different forum, but then all the nuances involved would be better suited for the calibration community to appreciate fully, so I'm posting it in here.
So the default stance of every calibration enthusiast is to turn off post processing. This is an exploration into what if not.
And its highly subjective.
I already owned a HDFury Linker (scales 1080p to 4k all framerates, no other resolutions), and recently bought a mClassic
(from Marseile Inc) as an impulse buy - finding out that both chained together produce next to no input lag, and significantly enhance some of my gaming sources (720p output) had me pleasantly surprised.
But the mClassic always had this distinct ringing around edges (oversharpening) I was kind of urked by - which is why I recently bought a DVDO iScan Mini (initially for the ringing filter, but its so much more) just to test it in this chain - and the outcome is -- fantastic.
Not so much on the 720p gaming sources I originally planned to use it with (DVDO iScan mini adds a little (beat em ups still playable) input lag with its scaler disabled (image enhancement can be left enabled seperately - so this is not a problem), and very noticeable input lag with the scaler enabled), but on 720p movie/tv sources.
To say it outright, the subjective impression of a low bitrate 720p internet source movie, becomes that of more than 1080p content of a high bitrate source. To put it bluntly - its day and night.
Almost jokingly - the result is 'best' with all three scalers chained, and here are their separate 'effects'.
TV input settings have all post processing disabled as usual (DVDO is faster to navigate and more granular, and also can be turned off (passthrough) at the press of a button).
Only upscales 1080p sources to 4k. Does so cleanly - does so without introducing noticable artifacting. Does a much better job of it than my B6 OLED from 2016 (which has a notoriously bad scaler). In my chain this is the last item before the signal goes into the TV. Compared to the DVDO iScan Mini upscaling an image to 4k, this adds more 'sparkle'. Its hard to explain otherwise, but the DVDO iScan Minis 4k output looks a bit dull in comparison. Its hard to describe why - there is no obvious sharpening or artifacting present - but thats just the visual impression I'm left with.
PC fonts are mostly left untouched - its just 'a good upscaler'.
DVDO iScan Mini
This is the second to last item in my chain - and its a post processing powerhouse. Two user setable preset slots, four presets in total. Much faster to access and tinker with, than your in TV settings, much more granular. Has the highest impact on subjective output quality overall. I use it exclusively for detail enhancement (-5/+5 scale), edge enhancement (same scale) and the deringing filter (because of the mClassic).
Produces most artifacts on PC fonts of anything in the chain. (If set to an ideal state for movies.)
This is the first item in my scaler chain. It mostly does edge enhancement (with ringing), but it also does some deblurring and some image smoothing, but only a very slight one - and also the best one of the scalers in my chain - with any reasonably detailed (even low bitrate) 720p source.
Can only output 1080p or 1440p - I use its 1080p output in my case.
PC fonts show noticable ringing with this enabled. But no other artifacts.
DVDO settings will depend heavily on the source.
I always have the deringing filter enabled.
I always have Output smoothing disabled (as the mClassic already does 'enough' on that front).
I always have basic settings like sharpness and others zeroed in
On detail enhancement, anything between 3 and 6 can be ok (depending on the source, slightly higher quality allows more enhancement - if the visual noise gets too much, you'll niotice it.
On edge enhancement anything between 2 and 5 can be ok, depends mostly on how the film was mastered. On 'soft' with frequent boka, or on cartoons you can push this higher, before the separation between forefront and background content becomes too comical.
This one is pretty easy to dial in, depending on the content. Also - interestingly this changes image characteristics similar to what a gamma slider would do - so it changes perceived image depth. On some content this makes the overall content look more 'natural' (pleasant) only because of that.
Again, the DVDO will by far produce the most artifacting on lets say a still interface image (f.e. Kodi Media Center UI), but it also produces the most positively noticeable effects on perceived image quality in film.
And, crucially - its interface is very fast, which means, you are actually willing to use it.
On the downside - on SD content, you have to dial in detail and edge enhancement much lower (about 2 for both (f.e. low preset)), or the image will just start throwing fake detail artifacts in your face like there is no tomorrow. Instantly noticable, and mostly unbearable.
The DVDO also has an OFF button on the remote, which quickly allows you to compare before and after - which is very nice as well. I frequently go through at least 3 presets per content and also look at the off state, it helps.
The DVDO also has a distinct info display for input and output resolution and framerate, which helps immensely. (LG Oleds do not.
Input chaining for me is
any resolution>mClassic>1080p>DVDO>1080p>HD Fury Linker>4K
All devices but the mClassic are 12bit capable.
None of the devices except for the HD Fury Linker are HDR capable - so this is a SDR only usecase.
As far as price is concerned, I picked all the devices up a the following pricepoints:
mClassic - 70USD
DVDO iScan Mini - 200USD
HDFury Linker - 80USD
And of course not at once, but over a few months, so I didn't notice up front, that I was 350USD into this, before I tested.
I've also put in an HDMI splitter, so I can look at the source quality without getting up and recabling.
The interesting thing for people in here probably would be to know the effects of all those different scalers, as well as the input latency they add ('none' for HDFury Linker and mClassic combined - more for the DVDO iScan mini, even more when it has scaling enabled (which it doesnt have to in my chain)), and what they do to the image.
Also the main input I want to leave you with is, that on 720p sources, the difference is night and day - and yes, it very much makes a difference that with the DVDO you can finetune postprocessing (detail/edge enhancement) depending on your source, which you cant (and wont do (slow interface)) with your TV.
edit: Oh, and my input source is 1080p (mClassic will still do the post processing, while then also outputting in 1080p), even with 720p sources. There are no postprocessing filters on the source (simple Android TV box in my usecase, running Kodi).