[Intel-gfx] [RFC 0/2] Enable Nearest-neighbor for Integer mode scaling

[Ville Syrjälä]

On Wed, Sep 04, 2019 at 08:32:09AM +0530, Sharma, Shashank wrote:
> Hello Ville,
> 
> On 9/3/2019 10:50 PM, Ville Syrjälä wrote:
> > On Tue, Sep 03, 2019 at 10:22:25PM +0530, Shashank Sharma wrote:
> >> Blurry outputs during upscaling the buffer, is a generic problem of gfx
> >> industry. One of the major reason behind this blurriness is the
> >> interpolation of pixel values used by most of the upscaling hardwares.
> >>
> >> Nearest-neighbor is a scaling mode, which works by filling in the missing
> >> color values in the upscaled image with that of the coordinate-mapped
> >> nearest source pixel value.
> >>
> >> Nearest-neighbor can produce (almost) non-blurry scaling outputs when
> >> the scaling ratio is complete integer. For example:
> >> - input buffer resolution: 1280x720(HD)
> >> - output buffer resolution: 3840x2160(UHD/4K)
> >> - scaling ratio (h) = 3840/1280 = 3
> >>    scaling ratio (v) = 2160/720 = 3
> >> In such scenarios, we should try to pick Nearest-neighbor as scaling
> >> method when possible.
> >>
> >> Many gaming communities have been asking for integer-mode scaling
> >> support, some links and background:
> >> https://software.intel.com/en-us/articles/integer-scaling-support-on-intel-graphics
> >> http://tanalin.com/en/articles/lossless-scaling/
> >> https://community.amd.com/thread/209107
> >> https://www.nvidia.com/en-us/geforce/forums/game-ready-drivers/13/1002/feature-request-nonblurry-upscaling-at-integer-rat/
> >>
> >> This patch series enables NN scaling on Intel display (ICL), when the upscaling
> >> ratio is integer.
> > I think we'd probably want a property for this sort of stuff. igt
> > could perhaps also use it to enable crc based scaling tests.
> I was initially planning to attach this to scaling mode property, 
> probably create a new option in there called "Integer mode scaling" or 
> we can use the "maintain aspect ratio" sub-option too. Do you think it 
> would make sense ? Or should we create a new property altogether ?

I was thinking a new prop. It would also expose the possibility of
adding even more filter/window functions. Maybe someone wants a
linear filter for instance.

> > Another problem is that we currently don't expose the panel fitter
> > for external displays so this would be limited to eDP/DSI only.
> > I have a branch that implements borders (for underscan) for DP/HDMI
> > which is at least moving the code a little bit into a direction where
> > we could consider exposing the panel fitter for external displays.
> 
> This would be very interesting, do you have any plans to publish this soon ?

I can send it out. Been hanging on to it because there's other pending
stuff on the list as well, but a few more patches probably won't hurt :)

-- 
Ville Syrjälä
Intel