[jd17]

Hello!

First of all - thanks for the great thread and work you have done here.

I have a few questions regarding scaling quality and methods.

I am currently using a RPi2 running LibreELEC 7.02 (Kodi 16.1) as my main device and I run Kodi on my Samsung Tab S 8.4 too.
In Android, I see the option "Enable HQ Scalers for scalings above 0...100%".
When playing a video the scaling methods to select are "bilinear" and "nearest neighbor", but changing does not seem to have an effect when HQ is enabled.
However all these options do not exist in any of the OpenELEC/LibreELEC RPi builds I used so far.

I am also considering buying an nVIDIA SHIELD box to replace the RPi2 once I buy a 4K TV. I want to be sure to get the best scaling on a 4K TV since the impact is so significant, especially when watching 720p or even SD sources.

Questions:
- Which scaling method is used on Raspberry Pis?
- Which scaling method is used on regular Android devices (e.g. my Tablet) with the HQ option?
- Which scaling method is used on the SHIELD with HQ enabled (if available)?


There is a big list of (apparently somehow manually selectable) scaling methods in the Kodi wiki:
http://kodi.wiki/view/video_playback

- Auto - If supported uses Lanczos3 Optimized when video resolution is lower than 720p (1280x720) and video FPS is lower than 30, otherwise it uses Bilinear.
- Bilinear - fairly simple and fast method (video resized with this method may appear slightly smoothed/blurred but with no edge halos also called ringing artifacts).
- Bicubic - more sophisticated method than Bilinear (more precise and slightly sharper video than Bilinear, but can introduce some ringing artifacts).
- Lanczos2 - 4-tap filter that uses a 2-lobe Lanczos windowed sinc function (sharper than Bicubic with less aliasing).
- Spline36 Optimized - 4-tap + 3-lobe filter, more precise than Lanczos2, which tries to produce the sharpest image with slightly less ringing artifacts then Lanczos3 Optimized (differences only noticeable with high resizing factors or when downsizing).
- Lanczos3 Optimized - 4-tap filter that uses a 3-lobe Lanczos windowed sinc function (comparable results to Spline36 Optimized, with less aliasing and more sharpness, but more ringing artifacts).
- Spline36, Lanczos3* - 6-tap filters that are more precise variants of above "Optimized" versions (they are sharper but might produce more ringing artifacts in some situations).

Characteristics of different methods:
- Sharpness - Bilinear < Bicubic < Lanczos2 < Spline36 Optim < Lanczos3 Optim < Spline36 < Lanczos3
- Aliasing artifacts - Lanczos3 < Spline36 < Lanczos3 Optim < Spline36 Optim < Lanczos2 < Bicubic < Bilinear
- Ringing artifacts - Bilinear (no ringing) - Bicubic < Lanczos2 < Spline36 Optim < Lanczos3 Optim < Spline36 < Lanczos3

*On GL builds these methods are slower than the optimized versions; this is the reason why they are not available by default but can be activated by advanced users in advancedsettings.xml

Are these somehow accessible on Pi, Tablet and SHIELD?

Thank you in advance!
Please tell me if this is not the right thread for these questions...
I just thought this might be of interest here since there is a big interest in best possible picture quality (proper 24p, good deinterlacing etc.)...